HYDROLOGTC PROPERTIES OF SEVERAL UPLAND FOREST HUMUS TYPES. IN THE LAKE STATES REGTON Thesis for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY WADE LOWRY NUTTER 1968 TTTT”7mmWWW 3 293 00795 9731 This is to certify that the thesis entitled HYDROLOGIC PROPERTIES OF SEVERAL UPLAND FOREST HUMUS TYPES OF THE LAKE STATES REGION presented by Wade Lowry Nutter has been accepted towards fulfillment of the requirements for Ph.D. Forestry degree in ‘ ‘\ 7‘ . f ) ///2§\ ’/C"5'( :L,I./;//( /, é ,,--- (elf; __ Major professor Date March 20, 1968 0-169 » BINBIIG IY HUAG & MS 880! BINDERY IND. LIBRARY, amoras L ................... ABSTRACT HYDROLOGIC PROPERTIES OF SEVERAL UPLAND FOREST HUMUS TYPES IN THE LAKE STATES REGION by Wade Lowry Nutter Forest humus has an important role in the evapora- tion and uptake of water in the forest soil profile. To better define this role for different humus types within a geographical region ten sites in Michigan were sampled that included a variety of soil and forest conditions and the three generally recognized morphological humus varients of mull, duff-mull, and mor. Undisturbed cores of the humus—soil complex, 16.5-cm diameter and 25.4-cm deep, were excavated from the profile keeping the humus-mineral soil interface intact. Rates of evaporation in controlled environment chambers were deter- mined by weight loss and water redistribution within the humus-soil profile during evaporation or infiltration was determined by the attenuation of a transmitted gamma radia- tion beam in 2.5-cm increments of depth. During two separate experiments each humus-soil core was subjected to a free water potential evaporation of 0.76 and 0.43 cm/day. Wade Lowry Nutter The humus classification used in this study is a system prOposed for the Lake States Region based on the degree of biological activity and organic matter incor- porated in the mineral soil. Based on the results of this study, the humus types were separated by their hydrologic properties into four groups, each independent of inter-site mineral soil variation. Listed by humus type they are l) mulls without an F horizon, 2) mulls with an F horizon, 3) more, including pseudo duff—mulls, and 4) duff-mulls. A continuous falling rate of evaporation was observed during a 50-day period with the humus horizons acting as a mulch to reduce the rate of evaporation to a rate lower than the maximum water transmitting properties of the humus-soil complex. The complexes of mull and duff-mull humus types held more water at 40-mb tension and the total evaporative loss was greater than in the mors. However, the mors lost by evaporation a greater fraction of the total initial water content than either the mulls or duff-mulls. Water was observed to flow against the humus-soil water content gradient during evaporation in response to an assumed matric suction gradient. At 50 days the loss from the 4- to 5-cm thick organic horizons of mors and duff-mulls was similar to that lost from the first 5-cm of mineral soil. In the mulls the loss from the surface S-cm was approximately twice that of the 5- to 10-cm depth. The F horizon ceased to lose water between 16 and 30 days Wade Lowry Nutter but the H horizon continued to lose water at a decreasing rate for the entire period of evaporation. When the F horizon was removed the initial evaporation rate increased. Total loss at 53 days remained the same for mulls and duff— mulls. In contrast, there was little change in the rate of loss from mors. During a simulated rainfall water advanced quickly through the soil as a wetting front maintaining the non— uniform shape of the initial water content profile except in the surface layer and at the end of the wetting front. The advance of the wetting front was similar in the mors and duff-mulls and also more rapid than in the mulls. During the simulated rainfall the F and H horizons resisted wetting and water moved rapidly through them into the under- lying soil. HYDROLOGIC PROPERTIES OF SEVERAL UPLAND FOREST HUMUS TYPES IN THE LAKE STATES REGION BY Wade Lowry Nutter A THESIS Submitted to Michigan State University in partial fulfillment of the requirements ' for the degree of DOCTOR OF PHILOSOPHY Department of Forestry 1968 ACKNOWLEDGMENTS The author is indebted to the members of the Guidance Committee--Drs. J. B. Harrington, Jr., W. J. Hinze, R. J. Kunze, and D. P. White (Chairman)--for their assistance and encourage- ment during the course of this study. The assistance and guidance offered by Dr. G. Uehara, University of Hawaii, while he attended Michigan State University as a post-doctorate fellow is also appreciated. The author and major professor, D. P. White, wish to extend their appreciation to Mr. Sidney Weitzman, former Chief, Division of Forest Protection and Watershed Management Research, North Central Forest Experiment Station, U.S. Forest Service, for his initial interest and funding of a forest humus classi- fication study for the Lake States Region and his continued interest and advice in expansion of this study to include hydrologic properties of humus. The work upon which this report is based was supported by funds provided by the United States Department of the In- terior, Office of Water Resources Research, as authorized under the Water Resources Research Act of 1964 and administered by the Institute of Water Research, Michigan State University. ii VITA Wade Lowry Nutter Candidate for the Degree of Doctor of Philosophy Final Examination: March 7, 1968 Guidance Committee: J. B. Harrington, Jr., W. J. Hinze, R. J. Kunze, and D. P. White (Major Professor) Dissertation: Hydrologic Properties of Several Upland Forest Humus Types in the Lake States Region Outline of Studies: Major subjects: Forest Hydrology Minor subjects: Soil Science, Geology, Micrometeorology Biographical Items: Born March 29, 1938, Pittsburgh, Pennsylvania Undergraduate Studies: Pennsylvania State University, 1956-1960 B.S. Forestry, 1960 Graduate Studies: Pennsylvania State University, 1963-1964 M.S. Forestry, 1964 Michigan State University, 1965-1968 Ph.D. Forestry, 1968 Experience: Assistant Sales Manager, Thompson Mahogany Company, Philadelphia, Pennsylvania, 1960-1962; Representative, Equitable Life Assurance Society, Philadelphia, Penn- sylvania, 1962-1963; Graduate Research Assistant, The Pennsylvania State University (University Park, Penn- sylvania), 1963-1964; Research Assistant, the Pennsyl- vania State University (University Park, Pennsylvania), 1965-1966; Graduate Research Assistant, Michigan State University (East Lansing, Michigan), 1965 to date. Member: Society of American Foresters Soil Science Society of America American Ge0physical Union Sigma Xi Xi Sigma Pi Phi Sigma Phi Epsilon Phi iii VITA . TABLE OF CONTENTS ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . LIST OF TABLES O O O O O O O O I O O 0 O O O 0 0 LIST OF FIGURES . . . . . . . . . . . . . . . . Chapter I 0 INTRODUCTION O O O O O O O O O O O O O C II. STUDY OBJECTIVES . . . . . . . . . . . . III. LITERATURE REVIEW . . . . . . . . . . . Humus classification . . . . . . . . Hydrologic properties of humus . . . IV. DESCRIPTION OF SAMPLING SITES . . . . . V. METHODS OF INVESTIGATION . . . . . . . . Sampling procedure . . . . . . . . . Instrumentation and theory of water content measurement . . . . . . . Determination of rates of evaporation and water content distribution . . Infiltration and redistribution of water 0 O O O O O 0 O I O O O O 0 VI. RESULTS AND DISCUSSION . . . . . . . . . Cumulative evaporation . . . . . . . Water content-depth profiles . . . . Discussion of unsaturated flow mechanisms as related to evaporation . . . Comparison of humus types by rates of evaporation and diffusivities . . Effects of F horizon removal on evaporation . . . . . . . . . . . iv Page ii iii vi vii 19 32 32 36 48 52 55 67 73 79 89 93 Table of Contents (Continued) Chapter Page Infiltration and redistribution of water 0 O O O O O O C O O O O O C O O O 97 VII. SUMMARY AND CONCLUSIONS . . . . . . . . . . . 101 LITERATURE CITED . . . . . . . . . . . . . . . . . . . 111 APPENDIX 0 O O O O O O O O O O O O O O O O O O O O O O 116 Table l. Humus, soil, and site descriptions; and location and site history for the ten sampling LIST OF TABLES sites in Michigan . Average humus and mineral soil horizon thicknesses for each core from the nine northern-lower and upper peninsula sites in Michigan . Per cent organic matter in each horizon of a randomly selected humus-soil core from each sampling site Initial water content, total evaporation, total fractional evaporation, and differences due to change in potential evaporation for 0 each representative core Average initial water content, total evapora- tion, total fractional evaporation, and differences due to change in potential evaporation for each site . Total fractional evaporation and total evaporation from the surface lO-cm at both potential evaporations for each representa- tive core . . Total fractional evaporation and total evaporation from the surface lS-cm at both potential evaporations for root mor humus type, core B-2 vi Page 20 23 31 69 7O 76 78 Figure la. lb. 2a. 2b. 3a. 3b. 4a. 4b. 5a. 5b. LIST OF FIGURES Well-develOped root mor humus developed on Kalkaska sand under a mature northern hard- wood forest, site B, Alger County, Michigan Mor humus develOped on Kalkaska sand under a mature northern hardwood forest, site B, Alger County, Michigan . . . . . . . . . . Mor humus developed on Blue Lake sand under a second growth northern hardwood forest, site C, Alger County, Michigan . . . . . . Pseudo duff-mull (mor) humus developed on Rubicon sand under a jack pine forest, site D, Alger County, Michigan . . . . . . . . . Duff-mull humus develoPed on Deerton sand under a second growth sugar maple forest, site F, Marquette County, Michigan . . . . Duff-mull humus developed on Graycalm sand under a second growth aspen and oak forest, site G, Wexford County, Michigan . . . . . Mull humus developed on Munising sandy loam under an old growth northern hardwood forest, site E, Marquette County, Michigan Mull humus developed on Blue Lake sand under a second growth northern hardwood forest, site H, Wexford County, Michigan . Mull humus developed on Mancelona sand under a second growth sugar maple and elm forest, site K, Wexford County, Michigan . Mull humus develoPed on Munising sandy loam under an old growth northern hardwood forest, site A, Marquette County, Michigan vii Page 25 25 26 26 27 27 28 28 29 29 List of Figures (Continued) Figures 6. 7. 0'.) o 10. ll. 12. l3. 14. 15. l6. l7. Cross-section of the humus-soil sampler and handle assembly . . . . . . . . . . . . Humus-soil sampler, handle, core, l/8-inch wire mesh bottom, and perforated steel band Gamma attenuation instrumentation and jig to hold cores and guide the source and de- tector for water content measurements . . . Calculation of “w by determining the sloPes of count ratio (I/Ic) as a function of aluminum thickness Xal . . . . . . . . . . Cross-section of the rainfall simulator . . Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core B-2, mor humus type . . . . . Cumulative fractional evaporation and water content profiles at each potential evapora— tion for core B-S, mor humus type . . . . . Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core C-5, mor humus type . . . . . Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core D—5, pseudo duff—mull (mor) humus type . . . . . . . . . . . . . . . . Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core F-4, duff-mull humus type . . Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core G-5, duff-mull humus type . . Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core E—4, mull with F horizon humus type . . . . . . . . . . . . . . . . . . . viii Page 33 35 4O 44 53 56 57 58 59 60 61 62 List of Figures (Continued) Figures 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core H-4, mull with F horizon humus type 0 O O O O O O O O O O O O O O O O O O 0 Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core K-S, mull with F horizon humus type 0 O O O O O O O O O O O O I O I O O O 0 Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core A-4, mull humus type . . . . . Cumulative fractional evaporation and water content profiles at each potential evapora- tion for core M-4, mull humus type . . . . . Hypothetical matric suction gradients devel- oped during evaporation as a function of core depth and time . . . . . . . . . . . . . Hypothetical moisture release curves for a humus horizon, h and mineral soil horizon, S O O I O O O C O O O O O O O O O O O O O O 0 Average diffusivities as a function of water content for representative mull, mull with F horizon, duff-mull, and mor humus types . . Effect Of F horizon removal on cumulative evaporation from mull and mull with F horizon humus types . . . . . . . . . . . . . Effect of F horizon removal on cumulative evaporation from mor and duff-mull humus types 0 O O O O O O O O O O O I O O O O O O O Infiltration and redistribution of water at average times in minutes for representative mull, mull with F, and duff—mull humus types . . . . . . . . . . . . . . . . . . . . ix Page 63 64 65 66 86 86 92 94 95 99 CHAPTER I INTRODUCTION A prominent part of the forest soil environment is the forest humus consisting of partially or completely de- composed organic detritus either overlying or intimately mixed with the mineral soil. It is a part of the forest which always changes, yet remains somewhat constant with time. Humus is continually supplied with new organic de- tritus throughout the year, the greatest input occurring at the beginning of the dormant season. Each addition is shortly transformed by chemical and biological decomposition to become a part of the uniform and distinct layers which show little change from year to year in an undisturbed state. Forest ecologists and soil scientists have long recognized the importance of forest humus and the underly- ing mineral soil in the development of forest succession and soil horizons. Forest hydrologists have been concerned with the development of these horizons and their influence on the hydrologic pr0perties of forest soils and the hydrologic cycle within a forest. Humus serves a well recognized function of interest to both the forest manager and forest hydrologist; first, 1 it protects the mineral soil surface from the impact of raindr0ps and the resulting erosion and reduction in infil— tration capacity, and second, it stores and transmits water. However, humus is responsive to changes in the forest en- vironment, whether this be catastrophic such as fire or less so in the form of livestock grazing or logging. A change in the hydrologic properties would be expected after such disturbances with reduced infiltration rates, greater surface runoff and erosion, and increased evaporation from the mineral soil. Approximately one-half of Michigan is forested and in view of the projected needs of domestic and industrial water supply, forests will play an important role in the future water budget of the state. It has been estimated that approximately two-thirds of the precipitation that falls on Michigan each year is returned to the atmosphere via evaporation and transpiration. The manipulation of the vegetation through forest management practices and the re- sulting changes in humus (as well as other environmental factors) may well affect not only evaporation and transpi- ration but the water resources of the state as well. Because humus is an important part of the forest affecting the hydrologic cycle it is important to have quantitative information on the hydrologic properties of humus to guide the forest manager in his multiple-use objectives. To understand the disposition of precipitation be- neath the forest canopy, the effects of humus on evaporation, moisture retention, detention, and transmission into the mineral soil must be fully evaluated. Just how much change in the physical properties of the humus-soil complex can be tolerated before the increase in evaporation or the decrease in infiltration capacity become detrimental to the objec- tives of watershed management is not fully known. What is known is explored in detail by Trimble and Lull (1956) in an excellent review of the hydrologic influence of humus and its application in the northeastern United States. They stress that to date quantitative interpretation is lagging behind qualitative recognition. Foresters and soil scientists have devised classifi- cation systems of forest humus based on the arrangement and physical properties of the humus horizons and mineral hori- zons with an admixture of organic matter. Although the quantity of literature on composition, classification and structure of humus is imposing, the information on hydrologic pr0perties for differing humus types within any one region is lacking. No attempt has been reported in the literature on classification that includes both hydrologic and morpho- logic properties although these are closely linked. Hydro- logic prOperties of humus horizons and mineral soil horizons dominated by organic matter are understandably governed by the physical properties of the organic matter, their principal component (Trimble and Lull, 1956). The objective of this study is to determine differ- ences in hydrologic properties of several upland forest humus types common to the Lake States Region and to relate these properties to evaporation loss and water content distribu— tion in the humus and soil during evaporation, and to water content distribution during infiltration. A basis for in- cluding hydrologic prOperties in a humus classification system proposed by White (1965) for the Lake States Region is also presented. This study was conducted in the laboratory under controlled conditions and provides information necessary for guiding later field investigations. Because this is one of the few studies involving different humus types within the same region and investigational methods are new they may have application in other regions. CHAPTER II STUDY OBJECTIVES This study represents one of the first attempts to evaluate the hydrologic properties and characteristics, par- ticularly as related to evaporation, of common humus types found within a specific region. Instrumentation was developed for the non-destructive measurement of volumetric water con- tent such that hydrologic properties of forest humus could be studied in relation to the underlying mineral soil, an important factor that has limited studies on undisturbed samples. Most past studies were conducted under conditions where the mineral soil—humus interface was disturbed and the humus studied apart from the underlying soil. Because liquid water in unsaturated soil will not move across an air-water interface but must move as a thin, continuous film from par- ticle to particle it is important to keep intact all humus and mineral soil horizons so continuity between the horizons is not disrupted. A field sampling procedure was develoPed whereby a core of the humus-soil complex could be removed from the soil profile keeping all horizons intact. The primary objectives of this study were: 1. Determine feasibility of combining hydrologic properties with other physical properties of humus 5 used in a classification system proposed by White (1965) for the Lake State Region. Determine the effects of humus type on rate of evaporation and total evaporation from the humus- soil complex. Study the redistribution of water that occurs during evaporation in the humus and soil horizons. Study the effects of F horizon removal on evaporation. Study the distribution of water with time in the humus and soil horizons during a simulated rainfall. CHAPTER III LITERATURE REVIEW Humus classification The classification of forest humus has traditionally been one of confusion because of the complexity and regional variability caused by the interactions of climate, topography, species arrangement and succession, soil parent material, faunal activity, and of particular importance, the past disturbance history. The basic classification guide in general use today is that of Hoover and Lunt (1952), however it is most suited to the classification of humus types on the glaciated soils of the northeastern United States. A simplified key with particular application to watershed management but retaining the basics of the Hoover and Lunt key is that of Trimble and Lull (1956). These classification systems are based on the arrangement and physical pr0perties of the three distinct humus layers as recognized by Hoover and Lunt (1952). They are: F - Fermentation layer consisting of partially decom- posed organic matter with origin of the material still recognizable. H - Humus layer consisting of well-decomposed, gener- ally black, amorphous organic matter where the origin of the material is no longer recognizable. Al- Surface mineral horizon typified by the accumulation of humified organic matter mixed with mineral soil. An additional organic layer, the L or litter layer, is some- times present in the humus profile as freshly fallen leaf litter but due to its transitory nature is not considered in the classification system of Hoover and Lunt (1952). Trimble and Lull (1956) suggest that litter may have important ef- fects on hydrologic properties during certain times of the year and therefore should be considered in hydrologic studies when present in the profile. Forest humus is broadly classified as either mor or mull, based on the degree of incorporation of organic matter in the mineral soil. A mor humus type is one in which there is an abrupt change from the H layer to the underlying min- eral soil; no organic matter is present in the mineral soil (A2 horizon). In a mull humus the H layer is absent and there is an A1 horizon with a strong admixture of organic matter. An intermediate humus type, with features of both mor and mull, has been termed a duff-mull (Hoover and Lunt, 1952). Each type includes several subtypes according to thickness, structure, and amount of organic matter. The Hoover and Lunt key is based on morphologic features and its application has proven contradictory in the Lake States Region as well as other regions of the United States(White, 1965). These contraditions are due in part to the state of forest humus terminology which Wilde (1966) represents as confused and chaotic and suggests a new system of terminology placing emphasis on readily determinable morphologic features of forest humus and their position rel- ative to the mineral soil. As expressed by White (1965) the fundamental problem in using a humus key in any region is the recognition and interpretation of decomposition processes and the nature and degree of biological activity which is taking place in the organic matter and upper mineral horizons with incorporated organic matter. Wilde (1958) contends that a morphological classification should be supplemented by the determination of chemical and microbiological properties. White's (1965) proposed classification refines that of Hoover and Lunt (1952) to be applicable within the Lake States Region. It is based primarily on the degree of bio— logical incorporation within the mineral soil as diStinguished from incorporation as illuvial colloidal organic matter. The distinguishing characteristics of the three common humus types as outlined by White (1965) are as follows: Mor - presence of an F and well-defined H layer at an abrupt boundary with the surface mineral horizOn which may contain infiltrated organic matter but shows no evidence of incorporation by faunal activity. 10 Duff-mull - shows some evidence of faunal activity; both an F and H layer are present as well as a biologically incorporated mineral-organic Al horizon as distinguished from illuvial colloi- dal staining. Mull - indicates strong evidence of incorporation of organic matter in the mineral horizon by bio- logical activity with no H layer present; a thin F layer may be present. The definition of the mull type humus corresponds to that of Hoover and Lunt (1952). A transition humus type common in the Lake States Region is also described by White (1965). Termed a mor in transition to a duff-mull, it shows some biological incorporation of organic matter in the mineral horizons but is not as well developed as a true duff-mull. A pseudo duff-mull, so called because of an apparent high organic matter content in the mineral horizons, is actually a mor because the organic matter is not biologically incor- porated but rather stained by illuvial colloidal organic matter. These two variants, mor in transition and pseudo- duff mull, are usually associated with a recent change in forest type as a result of drastic disturbance, i.e., fire or logging. Considerable variation exists in the literature on hydrologic studies in the use of the terms litter, forest floor, and humus. Rarely is an actual description of the 11 organic layers presented and the reader is confused as to the actual humus type and what organic and mineral horizons are present. This study will incorporate the terminology used by Trimble and Lull (1956): litter indicates current annual deposits only; humus designates the presence of an F and H horizon in mors or an F and A horizon in mulls; l and forest floor indicates the inclusion of all organic horizons (and Al in mulls) not excluding litter when present.' Hydrologic properties of humus As summarized by Metz (1958), the hydrologic impor- tance of forest humus has long been recognized: Litter (forest humus) does function effectively in reducing raindrop impact and subsequent erosion, in slowing overland flow and allowing more time for in- filtration of water, in maintaining surface soil in condition for rapid infiltration of water, and in reducing erosion by holding the soil in place. To this may be added the ability of humus to store water and to affect evaporation (Trimble and Lull, 1956). Humus has a high absorptive capacity for water but its chief function in controlling surface runoff is building and/or maintaining a macrostructure of the mineral soil cap- able of high percolation rates (Lowdermilk, 1930). Similarly, Trimble and Lull (1956) stress that humus also promotes faunal activity which tends to increase aggregation and porosity. Being highly porous, humus promotes rapid downward movement of water to the mineral soil and at the same time protects the soil from the destructive forces of raindrOp impact. 12 Perhaps more importantly, humus forms an obstruction and resistance to overland flow and thus holds water for in- filtration to take place over a longer period of time (Trimble and Lull, 1956). Disturbances suchas fire or logging can effectively reduce infiltration rates by exposing the mineral soil sur- face. On infiltration plots in upland hardwood stands of the Ozarks, Arend (1941) reported an average forest floor infiltration rate of 2.12 inches per hour as compared to 1.32 inches per hour for similar sites that had been annually burned for the previous 5 to 6 years. Mechanical removal of the L and F layers resulted in an 18 per cent reduction in the infiltration rate as compared to a 38 per cent reduction on burned plots. Arend (1941) explains the marked decrease due to burning to be the result of physical changes in the surface horizon in addition to a probable reduction in micro— biological activity. Trimble, Hale, and Potter (1951) compared percolation rates through small cores of individual humus and soil hori- zons collected in northeastern hardwood forests. They reported percolation rates of mors to be roughly twice that of mulls. Except in one instance there was no significant difference in percolation rates between subtypes within mor or mull classi- fications included in the study. In a lysimeter study in California, Rowe (1955) deter- mined the effects of ponderosa pine forest floor depth on infiltration. The lysimeters were filled with soil and then 13 covered with forest floor material collected in natural stands. Increases in forest floor depth from 1/4 to 1-1/4- inch had little effect on reducing surface runoff and in- creasing percolation rates through the soil. Thus, a 1/4- inch forest floor depth was sufficient to break raindrop impact and maintain soil structure for high percolation rates. A hydrologic property of forest humus that has re- ceived wide attention in the literature is its water storage capacity. Trimble and Lull (1956) contend that an increase in water storage capacity has several effects, most impor- tantly that of flood control where an increased retention provides more storage for large storms and an increased de- tention storage slows movement of water to the stream channels. They stress that any factors affecting humus type and depth will directly affect the water storage capacities. Another factor that has received some attention is the rate of water loss from storage after a storm. Infor- mation of this type, apart from hydrologic significance, could be useful in determining fire danger ratings (Blow, 1955). Helvey (1963), in a study conducted in the mountains of southwestern North Carolina, reported evaporation from the humus to be virtually ended 12 days after the last storm. The amount of water remaining in the organic layers was de- termined by covering a plot with a reflector to inhibit l4 evaporation and by assuming that after 24 hours all down- ward movement had ceased and water held in the humus was available for evaporation. Blow (1955), in a similar study in hardwood forests of eastern Tennessee, reported relatively stable water con- tents of the forest floor (mor humus) 14 to 16 days after . the last storm with field capacity reached in approximately 2 days. Rowe (1955) used samples of ponderosa pine forest floor placed in pans separated from mineral soil and deter— mined rates of evaporation assuming the difference between precipitation and free drainage to be the water available for evaporation. In these three studies, and others of similar nature, the authors have assumed that when field capacity is reached after short periods of free drainage all further downward movement ceases. The water detained in the humus is assumed available for evaporation. Using the procedures described above, Helvey (1960) determined that 3 per cent of the total annual precipitation was lost through evaporation from the forest floor. Blow (1955) reported 2 per cent, and Rowe (1955) 3 to over 5 per cent from forest floors ranging from 1.0- to 3.6-inches in depth. The presence of a forest floor, although a source of water loss as discussed, can also reduce losses in evapora~ tion from the mineral soil. According to Kittredge (1948), evaporation from soil underlying a forest floor is 10 to 80 per cent less than that from a bare soil. Rowe (1955) 15 observes that although evaporation from the forest floor can reach important amounts, this loss is more than compen- sated for by the reduction in evaporation loss from the underlying mineral soil. A mulch, as defined by Hanks and Woodruff (1958), is a medium which transports water only in the vapor phase. Although humus may not be considered a mulch in the agricul- tural sense, it may serve the same function. One difficulty in comparing humus to a mulch arises in specifying the depths of humus as compared to mulch; mor humus depth cannot be com- pared to mull humus depth because of the mineral soil incor- porated in the mull (Trimble and Lull, 1956). However, if forest humus dries quickly and its moisture content remains constant after approximately 12 to 16 days (Helvey, 1963; Blow, 1955), then it may act as a diffusion barrier and be a mulch as defined by Hanks and Woodruff (1958). Hide (1954) presents an excellent review of investi- gations prior to 1954 concerned with evaporation from soil. He lists two important variables which influence the rate of soil water evaporation: l) the vapor pressure difference between the layer from which water is evaporating (zone of evaporation) and the turbulent atmosphere, and 2) the resis- tance to vapor flow of the intervening layer. As long as the soil surface remains moist the principal resistance to vapor movement is caused by the thin layer of non-turbulent air adjacent to the surface. As soon as the soil surface becomes dry the resistance to vapor movement within the soil rapidly increases as the vapor moves through a thickening layer of dry soil. 16 The moisture flux from a soil by evaporation can be either steady-state or nonsteady—state under constant evaporative conditions. Steady-state evaporation generally occurs when the water table is near the surface. Lemon (1956), reviewing the work of the Russian investigator Kolasew, recognizes three stages of nonsteady-state evapora- tion. The first is a stage of rapid and steady loss de- pendent upon net effects of water transmission properties of the soil and atmospheric evaporative potential as deter- mined by wind speed, temperature, relative humidity, and radiant energy. This initial stage ends when a dry diffusion barrier develops at the soil surface. For a saturated soil the evaporation rate during the first stage will equal the potential evaporation from a free water surface. The second stage is one of continual decline in the rate of loss as the water content is depleted. The atmospheric conditions are no longer important and the evaporation rate depends solely on the water content distribution and the water transmitting properties of the soil (W. R. Gardner and Hillel, 1962). The third and final stage occurs at low water contents and is one of extremely slow water movement, most likely vapor diffusion. The effects of a mulch in reducing initial evapora- tive loss from a bare soil were reported by Russel (1939). He concluded that protection of the wet soil surface by a straw mulch from direct solar radiation was more important than the obstruction the mulch provided against vapor 17 diffusion. Mulches 3/4-inch thick were almost as effective in reducing evaporation as depths up to 6 inches. Studying the effects of wind on rates of evaporation from laboratory soil columns, Hanks and Woodruff (1958) reported that l/4-inch thicknesses of soil, gravel, or straw mulches placed on wet soil were as effective as l-l/2-inch thicknesses in reducing evaporation. Evaporation increased with an increase in wind speed which indicated there was an increase in turbulent mix- ing of air within the mulch itself. Thus, vapor transfer from the soil through the mulch was not a true diffusion process. The greatest effect of the internal turbulent mixing was noted in the more porous gravel and straw mulches. Studying the effects of a stubble residue on evapora- tion, Army, Wiese, and Hanks (1961) found a reduction only during the first stage of drying. This was attributed in part to a reduction in soil heating from radiant energy. Another reason was the increase in thickness of the relatively non- turbulent air layer above the soil, resulting in decreased vapor transport from the soil surface. After the soil surface dried, the effect of a mulch became less important and evapora- tion was controlled by the water transmitting properties of the soil. Benoit and Kirkham (1963) in a laboratory study found the rate of evaporation to increase with increased air move- ment and radiation for soil cores covered with 2 inches of either a soil dust, gravel or ground corn cob mulch. Although the samples were near saturation and the mulches were added so 18 there would not be a capillary break at the soil surface, a constant rate of drying was observed that was far lower than the evaporative potential. Although the experiment continued for 70 days a falling rate period of drying was not observed. Flow through the dry surface was by vapor transfer at a rate dependent upon the porosity of the layer. The water content distribution decreased uniformly with depth during evaporation from both mulched and unmulched soil columns. CHAPTER IV DESCRIPTION OF SAMPLING SITES Of the ten sites chosen for sampling in this study, seven were included in White's (1965) investigations to develop a forest humus classification key for the Lake States Region. Each humus type was classified by White after field examination and laboratory determinations of organic matter (loss on ignition), total nitrogen, and pH. Nine sites included in this study on hydrologic pr0perties are in the Spodosol (Podzol) soil region of the upper (northern) and northern part of the lower (southern) peninsulas of Michigan. All nine sites have a history of severe disturbance within the last 50 to 70 years. The re- maining site (sample M) was selected in a relatively undis- turbed forest in Michigan's southern part of the lower (southern) peninsula on a soil of the Alfisol (Gray-Brown Podzolic) group. The samples were collected in September 1966 before current year leaves began to fall. Soil and humus type, location and description of each site are presented in Table 1. At the end of the study humus and mineral A horizon thicknesses were measured on four cores from each sampling l9 table 1. Humus, soil and site descriptions; 20 and location and site history for the ten sampling sites in Michigan. Humus Soil Forest Avg.2 Type Site Type Type DBH inches Mull A Munising N. de. 15+ Sandy Loam Mor B Kalkaska N. de. 5.0- Sand 8.9 Mor C Blue Lake N. de. 5.0- Sand 8.9 Pseudo Duff- D Rubicon Jack pine 5.0- Mull (Mor) Sand 8.9 Mull E Munising N. de. 15+ Sandy Loam Duff-Mull F Deerton Sugar maple 5.0- Sand 8.9 Duff-Mull G Graycalm Aspen, Oak 9.0 Sand Mull H Blue Lake N. de. 7.5 Sand Mull K Mancelona Sugar maple, 9.4 Sand Elm Mull M Hillsdale N. de. 8.0 Sandy Loam 1 All soils are well drained. 2 Tree diameter at 4.5 feet above ground level. 21 Michigan Crown Location Stand Cover and County History per cent >70 Sec. 35 Selective cutting of pines T46W, R23W and hwds. 1850-1900 Marquette 40-70 Sec. 31 Clear out. 1900 T46N, R20W Alger >70 Sec. 18 Clear cut. 1900 T46N, R20W Alger 40-70 Sec. 32 Clear cut and burned. T47N, R20W 1850-1900 Alger >70 SW 1/4, Sec. 35 Selective cutting of pines T46N, R23W and hwds. 1850-1900 Marquette >70 NE 1/4, Sec. 15 Clear out. 1900 T46N, R23W Marquette >70 NE 1/4, Sec. 16 Clear cut and burned, T21N, R12W present stand established Wexford 1918. >70 NE 1/4, Sec. 15 Clear cut. 1900 T21N, R12W Wexford >70 NE 1/4, Sec. 31 Clear cut. 1900 T22N, R12W Wexford >70 SE 1/4, Sec. 30 Relatively undisturbed T4N, RlW Ingham since 1850. 22 site. Samples from site M were destroyed when the steel core was removed and horizon measurements were not possible. Each horizon contained in the 25.4-cm deep cores was measured at four equidistant points around the core's circumference. In many cases where there was a wide transition zone between F and H and between H and A horizons the actual point of measurement is arbitrary. Average horizon thicknesses for each core are presented in Table 2. After horizon thicknesses were measured each humus- soil core was photographed. A photograph of a 25-cm core from each site, except site M, is presented in Figures 1 through 5. Figure 1a, core B-2, is an example of a parti- cularly well-developed root mor with thick F and H horizons and an abrupt boundary between the H and A2 horizons. This sample is quite different from the other site B samples and is presented in this study as an example of water loss from thick organic horizons. The amount of organic matter in the mineral horizon, whether it be illuvial or biologically incorporated, is an important factor in the humus classification system proposed by White (l965)(see page 9). As previously discussed, or- ganic matter content is also an important factor in deter- mining hydrologic properties of the humus-soil complex. With this in mind, organic matter contents of each horizon, . . . 1 . expressed as per cent loss on ign1t1on, were determ1ned 1Samples were ground to pass through a ZO-mesh seive. Organic matter was ignited from a 10- to 20-gram sample at 700°C for 5 hours. Per cent loss on ignition is a weight loss determination. 23 Average humus and mineral soil horizon thicknesses for each core from the nine northern-lower and upper peninsula sites in Michigan. Table 2. Horizon Site-Core Designation A21 A22 A12 A11 F Humus Type centimeters 12.4 2 RfimDAR 10.0 10.2 8.8 10.3 1 m1Tm1T1T vg. 023.wRJA _ _ _ A.AA“A Mull RHRDAR 84252 0 04253 84443 51323 98551 31212 vg. 2.3A4ficA _ ._ _ BfibnuB Mor 667 6 oJBAUnn9 > 81557 03152 01373 21101 26974 31122 V annuficA _ __ _ CnCPCC Mor 603 o co RR888 > 68703 46635 04703 12142 45354 11111 9 v 023.4R3A _ _. . DnunuD _), F_r F.O um“ D( 011 d11 uuu acM S P 63206 73696 53123 21543 95530 0. 01011 V 2q3AaficA EfinpuE Mull 24 Table 2 (Continued) Horizon Site Core Designation A12 A21 A22 A11 F Humus Type centimeters Duff-Mull 01813 12011 V 923.4:3A _ .. . GGGG Duff-Mull 40638 01100 vg. 2445A _ _ _ HHHH Mull 58767 00000 Avg. 243455 _ KKKK Mull Trace This horizon extends below the sample depth (25.4-cm) 2 25 cmmwnoaz .hucaoo .cmmflcoflz .mpqnoo nomad .m nomad .m ouflm .umouom @003 cyan .umonom oooztnmn Gnocuuoc Iona: cuosuuoc oHsumE m noun: onsuma m Hound ccmm mxmmx wcmm mxmmxamm no womoao>oc IHMM co oomoao>ov mead: Hos .QH mmDUHm msebn.nos uoou comoaobovlaaoz .mH mmDOHm 'O;O O C . ’ c. . .’..'. '.".' :‘I‘Nlooogoocv. ..,N ‘ <1 . o. o o." , . 4.39... _. ., - 2...... r O 0000‘ 0" . ‘0'. ‘,".. .- 26 .'..."' ..‘Ona0"“.“. ' ‘0 0.. 9001‘. ’. ofifl-‘ofitw'» ,, A. . .rl'P ’ ~ .0 . *5 .'.......r.'.. .’0000000.O... ¢ '0 0 v, ,: O¢x.*,‘" 'Tb’OI-b 1 “-5,. «an. '4 V‘Wm"‘1544v: 11.51.91},44w.o$¢ \-’ , 0HNI11»$¢!W$¢£HI¢~ ine for- kp jac est, site D, Alger County, humus developed on Rubicon Michigan. Pseudo duff-mull (mor) sand under a FIGURE 2b. forest, site C, Alger County, growth northern hardwood Michigan. Mor humus developed on Blue Lake sand under a second FIGURE 2a. 27 .cmmfiaoaz .nmmflaoaz .mpnsou pnomxo3 .0 ouwm .mucnoo muuoswumz .m ouflm .umouom xmo new comma np3oum .umoH0m mamas Human nuzoum pcooom m Hmpcn pawn Eamommnw pcoomm m Hops: pawn counooa co pomoao>op uses: Hanfilmmno .nm mmson co pomoHo>op mafia: Haseummso .Mm mmstm ' I O f 0 . . t. A . . . 0 I v . d \ . o . l . . 0'. ~ ,. s . oi .‘ O o o o _l . . , .x . c a O. o . . .. .- . . i . ‘..%y . O o r . .. O . . n n . O V c t . . o . . . . o . . n O‘ .\ \ b o 4. a A . . . . C O l. I . . . f. . . . P... O v I; \ Xflfl . . e A. if. C O r .. ENE/«9-01 v.09! «(merit . q p. . ..., .. .. ... Q ' o 'O' 09.0 000 ----- O . '0... N P 28 .mchEMH xouuoo on» no puma pcm mafiumpflmo onv waco .coNflno: HHom ammo IGHE uo3oa ogu ca >ua>mo uoou .cmmflsowz 3oaaos on» ouoz .cmmflnowz .muczou UHOMxoB .m ouwm .umo .mucsoo opposvumz .m ouwm .umo IHOM poospumc cuonuuoc cpzoum thou pooapumc cuonuuoc nuzoum paooom m Hoods pawn oxmq pao cm Hopes Emoa hogan mcflmfi oSHm co pomoao>oo mafia: Hafiz .nw MMDme Ins: co oomoao>op mafia: Hafiz .M¢ mmeHm .0 9.. . o .. :3 "f '5 . I """'o"rs,\ ‘ a a I s s x v. O ‘fi'0.,. ’.100 “""I. o'.'.-.' . (1’ t I .# t . . . . - ca; . . ... .t . o a _ ._ . too, ovultvw 29 .cmmwsowz .cmmflsoflz .mucsou ouuosvumz .m ouwm .umo .mucaoo pnomxoz .M oufim .umoHOM thou poospumn choaunoc nuzonm Sam can dance Amman £u3oum 6H0 cm Hoods Emoa modem mcwmw pcooom m moons pawn mcoaoo Ins: co pomoao>op mafia: Hafiz .nm MMDUHm tam: co pomoao>op unads Has: .Mm mmstm w. to... . we. ... _H". H. 0.” .fl... .1.“ ... xi? OOuflf “a" .4 on... “i .. “06”" “CW 9. dunno a“. .... ”a.” 3. 3.me H. ... .......... .. I . ¢........ 60.. o. co. o...o.. .0... 0000.00; .u.. ...n .O'. .1. 30 for one randomly selected sample from each site. These data, used to verify field and laboratory classifications according to Whitels (1965) system, are presented in Table 3. Note the uniformly low illuvial organic matter contents of the mor mineral horizons as compared with the greater amount of biologically incorporated organic matter in the mull mineral horizons. Site D (Figure 2b), classified as a pseudo duff- mull because of organic staining in the mineral horizons, should be properly classified as a mor since the organic matter content of the mineral horizons is low (Table 3) and no biological incorporation is visibly evident in the hori- zons. Site G was classified as a duff-mull, however the H horizon in two of the cores was broken up and mixed with mineral matter. Because the H horizon was not continuous it was included as part of the A horizon (Table 2). One 11 of these cores, G-3 (Figure 3b), was selected for organic matter determination and the intermixing of pieces of H horizon is reflected in the high organic matter content of the A horizon (Table 3). ll 31 Table 3. Per cent organic matter in each horizon of a randomly selected humus—soil core from each sampling site. Per cent Organic Matter1 Horizon Site- Humus Type Core F H A11 A12 A21 A22 Mor B-2 67.3 38.0 2.9 0.6 Mor B-4 79.2 29.6 4.7 1.7 Mor C-5 77.6 36.8 4.9 0.7 Pgfigi°(33ff‘ D-3 63.4 36.0 4.6 0.7 Duff-Mull F-3 78.3 25.3 7.0 3.8 Duff-Mull G-3 79.4 25.7 9.2 Mull E-2 56.2 9.6 3.3 Mull H-3 78.6 15.8 2.4 Mull K-5 71.7 16.8 6.1 Mull A—4 16.1 0.7 Mull M-3 7.4 3.2 1Per cent loss on ignition 2See text for explanation CHAPTER V METHODS OF INVESTIGATION Samplingqprocedure To obtain an undisturbed sample of the humus and mineral soil a sampler was designed to cut a core 16.51-cm (6.5-inch) inside diameter by 25.4-cm (lo-inch) deep. The sampler is similar to the conventional Uhland soil sampler but cuts a core twice the diameter and three times as deep. This type of sampler permits removal of a soil core that is cut with a leading edge designed to minimize compaction and disturbance. A large diameter reduces the effects of water transmission at the soil-core wall boundary by in- creasing the ratio of core surface area to circumference. The larger sample also serves to reduce the variability common in humus. The core was constructed from 22-gauge (0.79 mm) galvanized steel with a soldered overlap seam on the inside. Boiler tubing with a 0.32-cm (0.125-inch) wall and 16.83-cm (6.625—inch) inside diameter formed the sampler. A beveled cutting edge was extended 2.54-cm (1.0-inch) below the core to facilitate cutting a smooth face on the bottom of the core (Figure 6). 32 33 T 23/4" Steel pipe handle 15" long / 1/4" x 3/4" bolts Figure 6. [.1 ‘jf3/4 Steel p1pe 29" long welded at base 1/4" x 1 1/2" steel TL 6.625" 10" +0.125" 6.500" Cross-section of the humus-soil sampler and handle assembly. 34 Upon positioning the sampler with core in place on the sampling site the F and H horizons were cut with a sharp long-bladed knife using the sampler's cutting edge as a guide. The sampling assembly was then pushed into the soil paying particular attention to keep it vertical. After digging the sampler out a square piece of plywood was placed on top to hold the surface humus layer in place and the en- tire sampler was carefully turned upside down. The sampler was slipped from the core and the bottom face of the soil dressed with a large knife and then covered with several layers of cheesecloth and a l/8-inch wire mesh screen. The screen was held in place by a perforated steel band tightened by a 1/4-inch bolt. The component parts of the sampler and core are shown in Figure 7. The field sampling site was first selected to cor- respond when possible to the exact location sampled by White (1965). A one-half chain square grid was laid out on a uniform site chosen to eliminate extremes in microtopography. Samples were taken at each corner and in the middle of the grid. A sixth sample was taken at random for a photographic record. If a sampling point happened to fall on a non-uniform spot (mound, depression, etc.) or too near a tree the grid corner was extended to the nearest uniform point. If unusual stoniness, rocks, or large roots were encountered the grid corner was extended until this did not occur. Generally seven to eight points at each site were sampled before five cores were obtained for investigation. 35 0 O o .0 0 0 t 0 0,009 . .0 0 . 0 0 0 0 0 0 . 0-0.0.00000.0. .000.0 0.’0000 0 0 . 0 0 0 0 01.0.0.0 0.0 30 0.0.0.0.0.u.0.0.0.0.000.0 . . . ... . .. . 0 0 . 0 . O. O 0 0 0 0 0 0 0 0 0 0 O. 0.... O.‘0. . Q 0 . O 0 0 0 0 . ”.‘u. 0 00.0....00.0.0.0...0.090.904.600.00.O. O O I r 0 0.0 ..H,v.0 0 0 0.0.0.0 0.0.0.0w000.0.0o0003.0.0.0.u 0 0 0 0 . 0 0 0 0 0 0 I o 0000”}.0000300000000...“.H.”."0H09 0. 0.0 . . 0.0 0.0 0.0-0... 0.0.0.0.0.0 03.000.03-00 00. .00... 0 0.0 0 0 0 0. . l 0.0.... .. O . . ..... .0 0.0 C . . 0 00000 0......00..00 .09. 0.00000 , . 000000000000. .. 0 I C . O C . ..O . . 0 m I 0 O 0 s 0 O 0 b O O O O O o 0 I 0 000.0.00000000000.0.0.0.00.0 .0... _ . 0.0 0.0 0 0.0.0 0.0.0000 0 0.0.0 0 0.0 0.0.0.0.0. 0.. . . ..O..c. .0. . . 0.0”...H. .0... Q .0.0‘).0.o'0.0.0 .I- O 0 b 00...000.000000.0000000.0.00.0.0.. . 0. .0. 0 0 0 0 0 0.0 0.0 0.0.0 0 0.0 0.0.0.0 0.0.0..0.0 0.0 0 . 0 0.. . .. 0.0 O 0 C 0.9.. O 0 .0. 0.. .0. O O 00... O '00....0..0.O...6.‘.0 Q o c o o .0"... . 0 . 0 . 0 0.0 o 0 000 0 0 o 0 0.0.000 D 0.90.7000.905000..00.0.0009 O 0 o 0 0 0 . 0 o 0 ..0200.0000.0.0.00.00000.0.00000000000 0.. . .0 .00000.000.000000000000 . .x. .0 0 0 . 0 0 I 0 . . Q . . . 0.00._.0.000000000.0.o.000 0 0. . 00000001000000000000. _ , . 00.00.. . .00000.0.00000000.0.0000 0.0 . p .00.0000000.00000.0.9.0 A. b”..0. .0 .... .0000000000000 .00 . ....000..0.00..0.000 Al..,//FFJ\.N/: O 0 0 0 . 0 0 0 a . . . o 0 . . .. . . . 0 . o. . . 0 0 0 O O o O O 0 . a 0 O O 0 0 . .0 0 a I 0 0 C 0 a o 0 .. 0 a u r 0 0 0 0 O 0 v .0 a o O o o 0 O O . r 0 0 0 0 0 . 0 0 0 O 0 a . v 0 0 O 0 0 0 0 0 I o a I O o 0 o 0 . O 0 0 o D i D l O O 0 0 0 o O o 0H 0 . I . 0 0 0 0'00 0 0 0 0 I 0 . .. 0 D O 0. . 0 o 0 I u 0 .. 0 r O 0 0 0 0 0 0 0 . . 0 0 0 0 0 0 0 0 0.. 0 . 0 0 I O Q 0 0 O . . O Q 0 .0....0..0000 0... 0.0.0000...0 0 0 0.. O O O O O 0 O .0.‘O.: . O 0 O :0 0......0 000. 0...... .0090 CO... ...lo 000000000 .000 ..00..000000 000 . 00 0000 0..0.000. 0 \‘or0oOO... 0 . .000. O. 0. .0. H...’C.O..C..O. ..‘.‘0......I.0 0.0 0.0.0.0.... 000000.000. o ..‘0...Ou0.0 900.0 0 0.0.0.0-v 0.00.0.0 . “.-.‘... ...0. .0 . ...0... O .0. .0... 0.000 000 I 0.0 9.00. 0.0. 0.00...- ..‘0.0.0 .00...0.O.O.. 0 .0..'.” .0'...’.. v9.00... 04.0.C .0. '0’. I 000.0. .‘a 000000.000.0 ..0000.0 V0...’......0 .C’l'.... 0.. 000000 0000000 0 000000 0.. 00 "00.000 0.000.000.0- 00 0000 4 I000 00 i0 0 0 .0000 00000 0.5.104. .0000. 00.0000 000 00.0: a n a . 0,0000 .00 III: .I: 000.00000/00000000 .. I a .. .. . a. 00 : 0~FVEQZ$ ' h wire -1nc 1/8 mesh bottom and perforated steel band. Humus-soil sampler, handle, core, FIGURE 7. 36 Instrumentation and theory of water content measurement To determine changes in water content with depth in the humus—soil core it is necessary to use a non- destructive, high resolution technique of measurement. This can be accomplished by using the principle of attenua- tion of electromagnetic gamma radiation as it is transmitted through the soil or humus. The gamma attenuation method is based on differences in attenuation of a monoenergetic beam as it is transmitted through a column of soil of varying density. If the density of the soil less its water content is assumed to remain con- stant, then any change in the attenuation of the transmitted A beam is due to a change in the water content. Although the principle may be used to measure bulk density (van Bavel, Underwood, and Ragar, 1957), the technique has proven suc- cessful in the laboratory as a means of measuring changes in water content of unsaturated soil columns (Ferguson and Gardner, 1962; Gurr, 1962). The instrument used in this study is a portable, self-contained unit manufactured by Troxler Electronic Labo- ratories, Raleigh, North Carolina and specified as the SC-lO Two-Probe Density Gauge. It employs a scintillation detector to detect the intensity of an attenuated gamma beam trans— mitted through soil from a 5 mc. Cesium 137 radioactive source. The scintillation detector consists of a 1.5-inch diameter by 0.5-inch thick NaI(Tl) detection crystal directly 37 coupled to a photomultiplier tube. The detector probe and source are designed to fit in standard aluminum tubing of 1.9-inch and 0.75-inch I.D. respectively. High resolution is possible when amplified electronic pulses from the detector probe are fed into a single channel pulse height analyzer for electronic discrimination of low energy scattered or partially attenuated photons. A standard Troxler Model ZOO-B scaler counts all non-discriminated pulses from the pulse height analyzer. Both instruments are internally powered by rechargeable nickel-cadmium batteries. Cesium 137, with a half life of 27 years, emits low energy photons with a peak energy of 0.661 Mev (million electron volts) and is preferred over high energy sources because water is a poor absorber of high energy gamma rays (W. H. Gardner, 1965). The manner in which photons of the incident energy are attenuated when transmitted through matter is exponential as expressed by the following law: I = 10 8X9 [-(upX)] (l) where I0 is the incident intensity of the source in counts per minute (CPM), I the transmitted intensity through a sample of thickness X (cm), p the density (g/cm3) of the absorbing material, and u the mass attenuation coefficient (cmz/g), a function of both the radiation energy and the absorbing material. For any mixture of elements the mass attenuation coefficient is the sum of the individual mass attenuation 38 coefficients for each element on a weight fraction basis. All the elements of a dry soil, except hydrogen, have nearly equivalent mass attenuation coefficients. For ex- ample, the average theoretical mass attenuation coefficient of oven-dry soil for nine representative U.S. soils was determined by Reginato and van Bavel (1964) to be 0.0775 cmz/g at 0.662 Mev. In contrast, the mass attenuation co- efficient for hydrogen at the same energy is 0.1538 cmz/g. Hydrogen constitutes a very small weight fraction of dry soil and the density can be determined from a graphical solution of equation (1) by using either two standard ab- sorbers of different density such as aluminum and magnesium or one standard absorber of varying thickness. Because the mass attenuation coefficient is both additive and independent, equation (1) can be written for a moist soil as I = IO exp [—uspS + uwpw)x] (2) whereuspS and “wow are the mass attenuation coefficients and densities of soil and water. The value pw may be ex— pressed as the volume fraction of water or the water content , 3 6 (g/cm ). A direct method derived from equation (2) for deter- mination of the water content 9 in soil columns, attributed to W. H. Gardner (1965), is = — X— Im I0 exp [ (uspS +-Uwpw) Zucpcxc] (3) 39 and Id = IO eXp [-usosX - Zucocxc] (4) where 1m and Id are the incident intensities through moist and dry soil and “CDC and XC are the mass attenuation co- efficient, density, and thickness of the container. Divi- sion of equation (3) by (4), transposing and substituting 0 for pw yields ln(Im/Id) UwX (5) If only the peak energy of 0.661 Mev is used, i.e., collimation and electronic discrimination eliminate all scattered and secondary radiation, the established theoreti- cal value of “w can be used for a solution of equation (5). Perfect collimation and electronic discrimination are rarely attained but satisfactory results are possible when a range of energy about the peak is used including some scattered and secondary radiation. In this case equation (5) must be solved using a mass attenuation coefficient empirically de- rived for each range of energy and each instrument and geometry of design (W. H. Gardner, 1965). For example, Gurr (1962) successfully determined water contents in soil columns by counting the transmitted energies between 0.50 and 0.66 Mev and using an empirically derived pw. The apparatus constructed to facilitate humus-soil water content measurements is shown in Figure 8. The FIGURE 8. 40 ppppp 00000.00.- Oloooosns o O o o C O O O . O I o O 0 0.0.9 o C 9 o O I 0 O .000 0 $0000 . ......oo.000000 ..,..o.00.000t~ '.'...........0 .QOOQIOOOOtooo. 00060000000090. QQOOOOCOOOOOOOO OOOOOOOOOOtOOO~ QOQOOOOOOOOOOOQ' goooooOOOOOOOOODOOa ...o-ocoooooooooooooco~ ...ooo¢o.oo.0000009090o cocoooootOOOOOOOOOOOOOs ..oooooooooooooooooo~o~ goo-oOOOOOOOOOOOOOOOOOI .rooooOOOOOOOQIOOOOOOI .0000000000O009000‘0404 QOOOOOOOOOOOOOOOOOOOOOQ 90000000000009.6090009¢ OODOQOOOOOOOOOQOOOOQQOQ 1M.‘OOOOOO0.00000000000¢ OOCOOOOOOOOQOOOOOOIOOQ COCO-OO’QCCC.0.0U90000 OOOOOOOOOOOOOOOOOOOOOo 00.000000000000000... OOOOOOOOO’OOOOCOOOOOI OOOOQOOOOOObQOGOO'... 0.0000000690000000004 00000000000060.0000. 00900009900000.0900! 00000000990000.0000 000.000.900.0009004 OOOOOOOOOOOOOQQQQQ4 OOOOOOOOOOQQo... .“.‘.......‘ OOOOQOOfl 0.00.000 OOOOQ¢ .0000... 000.000 ....h... ..’.“.Oto‘.; 'OOOQooooooto-o~ O Q Q o a I I I 0 o o O o O O O 0 O ...Q..OO$.I.O‘IO¢G O I O O O o C ‘ o o o t 0 o O a O .’.....QI.. ..~........-I 00690099000 ‘0090000000 00.00000... 00...... 00.0.0900 0.0.0.0000. OOQOQOO¢"' 0.00.000... 09.0.0.0... 900000000000 Cocooooooofi" 00.00.90.000 0.00.000... 0.00.0090... ooooooooo‘ Otfiooooooo 9'0 O.‘HV.O* O -0 Gamma attenuation instrumentation and jig to hold cores and guide the source and detector for water content measurements. The scaler with ratemeter and high voltage power supply is the instrument on the right and the pulse height analyzer is on the left. Between the two is the variable speed control for the motor used to move the detector probe and source. 41 137 source were 12 inches (30-5 cm) detector probe and Cs apart, center to center, with the source placed in an alumi- num tube 0.75-inch I.D. and the detector probe in an acrylic plastic tube 2.0-inch I.D. To permit free movement of the detector electronic cable a slot was cut in the side of the plastic tubing facing away from the source. The aluminum tube containing the source was surrounded by lead shielding 3 inches in diameter with a slot equal to the 0.875~inch O.D. of the tubing in the lower 12 inches facing the detector probe. The upper 10 inches of solid shielding was for source storage. A 1/50 H.P. variable speed D.C. motor quickly and simultaneously positioned the source and detector probe with 1/16-inch diameter nylon cord attached to fishing swivels to prevent twisting. The humus-soil cores were centered between the source and detector on a platform for exact positioning each time water content measurements were made. Two energy levels were used in measuring water con- tents of the humus-soil cores. Only energies between 0.550 and 0.575 Mev resulted in a linear relation between -1n (I/IO) and density p or thickness X. The second energy level of 0.661 - 0.691 Mev resulted in a non—linear relation similar to that reported by Thames (1965). When Thames improved the beam collimation in addition to the already present electronic discrimination a linear relation was obtained. However, Reginato and van Bavel (1964) obtained a linear relation without using collimation, depending on electronic discrimina- tion alone. The reason for the non-linearity observed in the 42 current study is not clear. It is possible that a combina- tion of instrumentation, geometry of design, and lack of collimation were responsible. The lack of collimation may not be as critical when the slightly lower energies, 0.550 - 0.575 Mev, are counted and a linear relation exists. Careful checks were made of known water contents in a quartz sand by gamma attenuation at each of the above energy levels. Results were comparable, indicating that the non-linearity did not seriously affect the accuracy of water content measurements. Calibration procedures were identical for both energy levels used and the discussion to follow will be concerned with calibration results from the 0.550 - 0.575 Mev energy level. Theoretically, the volume of soil measured by a transmitted beam will be a solid angle from the point source subtended by the scintillation crystal. Using similar in- strumentation without collimation and depending on electronic discrimination only, van Bavel (1959) showed that a vertical resolution approximately equal to the thickness of the crystal (0.5-inch) is possible. The resolution of the instrumentation used in this study was checked by passing an aluminum plate 0.79-cm thick through the beam at‘a point equidistant from source and detector. For energies between 0.550 and 0.575 Mev the vertical resolution was approximately 0.6 inches (1.5-cm). Calibration was required to find the value of “w in equation (5) to solve for water content 0. A tray was con- structed inside a standard, empty soil-humus core that would 43 hold 36 aluminum plates, each 0.397 cm thick, normal to the transmitted gamma beam. The tray would hold either aluminum plates, water, or combinations of both. To determine uw it is necessary to solve the follow- ing equation I/IC = eXP [-(ualoalXal + uwowxw] (6) where Ic is the intensity of the transmitted beam through the empty standard core. Count rates of the transmitted beam I were determined for various thicknesses of aluminum and aluminum-water combinations. For the aluminum-water combination an equal thickness of water was added for each aluminum plate removed. These data are shown in-Figure 9 in a plot of -ln(I/IC) as a function of aluminum thickness X al' The lepes, Halo and “alpal' were used to al — L1wpw solve equation (6) for UW. Calculation of each set of slopes in Figure 9 for solution of equation (6) results in a mass attenuation co- efficient for water of 0.0623 cmZ/g as compared with the theoretical mass attenuation coefficient of water at 0.662 Mev of 0.0862 cmz/g. Thus, the value of ”w calculated is valid only for this instrumentation, geometry of design, and range of energy counted. According to W. H. Gardner (1965) the precision of gamma attenuation in water content measurements varies with the thickness and density of the soil core, the mass atten— uation characteristics of the soil, and the magnitude of 44 filope = (“alpal - u p ) 0.0806 1.4- 1.2 U H \ :1 g 1.0 7 Slope = “alpal = 0.1429 .8 ' .6- _ Llalpal - (“alpal - “wpw) .4' Uw pw _ 0.1429 - 0.0806 — 1 .2- = 0.0623 cmz/g I l J l I 4 l l l I r l r 0 2 4 6 8 10 12 14 0.2 0.4 0.6 0.8 1.0 1.2 Thickness, X - cm a1 Densit p - /cm3 -YI a1 9 Figure 9. Calculation of “w by determining the lepes of count ratio (I/IC) as a function of aluminum thickness xal' 45 the counts Im and I in equation (5). The standard devia- d tion in water content, as derived by Gardner, is given by the equation (7) when Id is counted over a period 3- to 4-times longer than Im' For the range of Im between 20,000 and 85,000 CPM ex- perienced in this study the average precision in water content 0 is 0.010 g/cm3 (i.e., 1.0 per cent water content by volume) at the 95 per cent confidence level. Accuracy was determined by comparing calculated values of 0 from equation (5) with actual values of 0 in a known sample. Medium quartz sand was packed to a dry density of 1.433 g/cm3 in a standard core to a depth of 3 inches. The water content was changed by adding a known quantity of water with an atomizer to the quartz spread out on a plastic sheet, thoroughly mixing, and repacking in the core to the required volume. For 6 between 0.085 and 0.410 g/cm3, the latter being saturation, the values of 8 deter- mined by gamma attenuation Were an average 7.7 per cent lower than the actual values of 0. At a water content of 0.200 g/cm3 this represents an accuracy of 0.015 g/cm3. Similar counts through a standard absorber were not possible at the beginning of each period of instrument operation because the detector photomultiplier tube voltage supply could not be finely adjusted. Thus, all values of Im and Id were adjusted to correct for the difference in 46 standard count rates. Five minute standard counts every 20 to 30 minutes during instrument operation were used to correct for any drift that occurred. The standard counts, Ial' were taken through a standard absorber of an empty core with aluminum plates normal to the beam. A second standard, an empty core, was used to check the ratio Ial/Ic' Frequently differential drift would occur and the ratio would change making “w invalid. If this change was significant measurements were terminated and the instrument readjusted to give the proper ratio. At the end of the study each core was oven dried at 105°C for one week after the temperature had been slowly elevated over several days. Very little shrinkage was ob- served since most of the soils were sand with only slight amounts of fine textured material. The humus horizons, already slowly dried by evaporation, did not exhibit ex- cessive shrinkage except in a few isolated cases. What shrinkage did occur was observed to be laterally away from the sides of the core and not longitudinal. Lateral shrink- age will not significantly change the count rate because the quantity of solid material within the zone of measure- ment between the core walls remains the same. After drying, I was counted for 3 minutes at each d depth and water contents were computed by equation (5). All computations were done on the Michigan State University CDC 3600 computer. With knowledge of I and Ic’ the data d in Figure 9 of -ln(I/Ic) and Xal can be utilized to determine 47 density of mineral soil assuming “a1 = “s as demonstrated by Reginato and van Bavel (1964). The assumption that “s is valid for humus and mineral soil with large amounts of incorporated organic matter is questionable due to the in— creased quantity of hydrogen in organic matter. This assumption is valid for organic matter contents in mineral soil less than 5 per cent (inferred from data presented by Reginato and van Bavel, 1964) and would probably hold for organic matter contents as great as 10 per cent. Assuming the validity of Us for humus will result in an underesti- mation of the humus density. To account for the increased hydrogen content in humus a mass attenuation coefficient should be determined for several ranges of organic matter content encountered. This is a time consuming procedure and beyond the sc0pe of this study. Raginato and van Bavel (1964) describe a technique to determine the actual mass attenuation coefficient for soils which could be adapted for humus. A least squares equation fit to the data of -1n(I/Ic) and pal was used to determine the dry density (g/cm3) of mineral soil and to estimate that of humus. The average density of each aluminum plate used in calibration was 2.677 g/cm3. For 36 aluminum plates between the source and detector 30.5-cm apart the effective density was 1.255 g/cm3. A scale of density is shown in Figure 9 along the X-axis to correspond with thickness of aluminum. 48 Determination of rates of evaporation and water content distribution Evaporation experiments were conducted in a Sherer- Gillett (Marshall, Michigan) Model CEL-512-37 environment chamber equipped with a Dryomatic (Alexandria, Virginia) Model 150 dehumidifier. Temperature and humidity within the chamber were controlled by a pair of wet- and dry-bulb temperature sensors.~ Evaporation loss from the humus-soil cores was determined by weighing each core at approximately 2 to 3 day intervals. Water content distribution was de- termined by gamma attenuation at 2 to 3 week intervals during evaporation loss. Two separate experiments with different potential evaporation conditions were conducted in the same environ- ment chamber, each over 7 weeks in duration. During each experiment the temperature was maintained at 24 i 0.6°C, 4 cal/cmz/min, and the the radiation level was 6.04 x 10— air circulation in the chamber remained constant. Relative humidity in the first experiment was 40 i 2 per cent and in the second was 70 i 2 per cent. This resulted in an average potential evaporation, expressed in depth of water evaporated from a free water surface in several standard cores, of 0.76 and 0.43 cm/day respectively. The radiant energy was sup- plied by a bank of incandsecent bulbs to simulate the near infra-red light quality normally found beneath a forest canopy. Forty samples (four of the five from each sampling site) were prepared for each experiment in an identical 49 manner. The samples were wetted from the bottom in tubs by raising the depth of water one inch each day for 10 days, then remaining at saturation for five additional days. After saturation the cores were placed on tension tables at 40-mb (one millibar equals approximately one cm water) tension on the bottom of the core, a total 65-mb tension at the top. Fine quartz sand of 70-120 mesh covered the paper on the tension table assuring contact with the soil through the l/8-inch wire mesh on the bottom of each core. Equilibrium, as established by weighing, occurred in all cores within 3 days. Plastic bags covered the tops to pre- vent evaporation during all phases of preparation. After removal from the tension table a plastic cover and lid from a one gallon bulk ice cream container formed a base. A tight seal was made around the base with masking tape. The cores were arranged in four blocks, one core from each sampling site in each block, equally spaced over a 53- by lOO-inch steel mesh plant bed in the chamber. The blocks, and cores within the blocks, were randomly arranged for each experiment. Water loss by evaporation was determined by periodic weighing on a tOp loading automatic balance with an accuracy of :1 g. This evaporation loss E, expressed as depth of water in centimeters, is calculated for any time period from the relation _ dS E — Fit (8) 50 where dS/dt is the water loss S in grams from the humus-soil core during a specified time interval t in hours, and A is . . 2 . . the cross-sectional area in cm . Cumulative evaporation for a time interval t2 - tl is defined as t2 / Edt = AS/A. (9) t1 Cumulative fractional evaporation is also determined and is simply cumulative evaporation at any time divided by the total initial water content at 40-mb tension. Water content distribution within each core was determined at eight depths by gamma attenuation before evaporation began (t = 0) and at approximately 2, 4 and 7 weeks thereafter for each experiment. Water content mea- surements were made at the center of one-inch increments of depth, except at the surface, because the physical di- mensions of the scintillation crystal and resolution precluded smaller increments. The source and crystal were centered at depths from the surface of 0.75, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, and 7.5 inches corresponding to 1.9, 3.8, 6.4, 8.9, 11.4, 14.0, 16.5, and 19.0 cm. Each core, when removed from the chamber during water content measurements, was covered with a plastic bag to prevent evaporation. Total time out of the chamber for each core was generally less than 30 minutes. A third evaporation eXperiment was conducted on the remaining fifth core from each sampling site to observe 51 the effects on evaporation by removal of the F humus layer. The cores were prepared in the same manner as in the first two experiments and evaporated in the chamber at the same constant conditions and 40 per cent relative humidity. At the end of eight weeks the cores were saturated and drained as previously described, the F humus layer removed, and the cores placed in the chamber under the same conditions for the same period. To simulate the conditions in the chamber as applied during the first two evaporation experiments, the 10 cores in the humus removal experiment were arranged in a single block with 30 empty cores filling the remaining blocks. Evaporation rates were determined by weight loss as in the earlier experiments. Water content distributions were not measured. Biological activity in the humus and soil horizons no doubt continued during the evaporation experiments. Earthworm activity in the mulls was most evident in the form of new casts deposited on the surface. Other visible evidence of change in humus structure due to biological activity was not noted. When the samples were not in use, the biological activity was arrested by storage at 4°C. Due to relatively low evaporative potentials the humus and soil horizons dried slowly. Lateral shrinkage, restricted to the surface of the F layer, was observed in a few cases. All visible changes, when they did occur, were noted throughout the study. 52 Infiltration and redistribution of water To study the water transmitting properties of the humus horizons, simulated rainfall was applied to one core from each site selected from the group previously used in the evaporation experiments withE‘horizon intact. Changes in water content during and after application were measured by gamma attenuation. To apply water uniformly and at a constant rate a rainfall simulator was constructed similar to one described by Adams, Kirkham, and Nielsen (1957). The simulator (Fig- ure 10) consisted of an acrylic plastic reservoir, 16.25-cm I.D., in which raindrOp applicators were supported 5-cm above the humus-soil surface. The raindrop applicators were 0.635-cm O.D., 0.152-cm (0.060-inch) diameter bore, 2.54-cm long glass capillary tubes with 0.129-cm (0.051- inch) diameter Chromel-A wire 2.8-cm long supported in each. One-hundred fourteen such applicators were arranged 1.3-cm apart in six concentric circles and affixed in two round plastic plates 2.6-cm apart. A pressure head regulator as described by Adams, gE_§1. (1957) was used to maintain a constant head in the reservoir of 0.6 cnn producing a simulated rainfall of 3.0 cm/hr (1.18 inch/hr). The cores selected for the infiltration study were saturated and drained on the tension table following the same procedure outlined for the previous experiments. 53 Acrylic plastic-Z 16.25 cm 17.0 cm , 7,. - , s 5,. , _ , , ,i_ ,- + - - - - - - - - - - - - «f. Chromel-A wire in 5.0 cm capillary tube ‘ L. L— L Figure 10. Cross-section of the rainfall simulator. See text for explanation. 54 Because of the coarse texture of most soils used in this study the rate of water movement is rapid at high water contents and water applied to the surface will move too quickly to follow with the type of gamma attenuation in- strumentation used. To avoid this problem the cores were subjected to a high evaporative potential to decrease water contents before applying simulated rainfall. Generally 1.5- or 2—cm of water was applied in ap- proximately 30- or 40-minutes depending on the texture of the soil. The core bottom was open to the atmosphere so air could move freely ahead of the wetting front. Imme~ diately before applying simulated rainfall the initial water contents were determined by gamma attenuation at the same eight depths used in the previous experiments. Mea- surements following the wetting front continued during and after application at approximately one-minute intervals until redistribution was slow, at which time they were spaced over longer intervals until the wetting front reached the core bottom. CHAPTER VI RESULTS AND DISCUSSION The variation in rate of evaporation and cumula- tive fractional evaporation among replicates or samples from each site was slight and these results can be presented as an average for each site. However, due to differences in depth and physical arrangement of horizons in relation to the point of water content measurement, water content-depth profiles in each sample from a particular site varied con- siderably preventing the determination of an average water content—profile for each site. For the purpose of illustra- tion and discussion an average sample was chosen to represent each site. These selected samples will be termed representa- tive but must not be considered to fully represent all conditions at each site. Cumulative fractional evaporation and water content profiles as functions of time and potential evaporation are presented in Figures 11 through 21 for each representative core. Organic and mineral horizon depths are indicated in relation to total core depth on the water con— tent profiles. A complete tabulation of cumulative evaporation ex- pressed as depth of water in centimeters, cumulative 55 56 Volumetric Water Content o .10 .20 .30 .40 .50 .60 0 ‘ F n P E O ___ a) — 2' A: .p Q: 0) ‘ A " D ‘ ” 0 0d 22 0 0d (Una Al6d A17d 20r E130d - E33d v51d V53d 25- L PE = 0.76 cm/day PE = 0.43 cm/day .8- <3 PE = 0.76 cm/day 8 13 PE = 0.43 cm/day "-1 '7' 9 4.J (U 6' m .6- a m f > J m c . H '5? . ”6’45 m ’ .,r;7' 8 I’A" O :3 .4" '5 Ifl/A’ O-H 0 ° ,/€?’ ’,a S '1 /.// ’I” [LI .3_ '1 // ’/”” 6 AK IJY' .: , A/ / fl .2? r g” /// l l/ / ,—{ A’ / s 6 ,’ o ‘,/ 5 /’A ’A’ U 01. ’1/ ”/’ _.... 1. ————-— 3 ‘A ”A,/’ ___..—-———-" 0*“ fi— Lr"—:—' 1 l . 1 1 1 l L 0 10 20 30 40 50 Time-days Figure 11. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core B-2, MOR HUMUS TYPE. Depth-cm 20 25 Cumulative Fractional Evaporation 1 Figure 57 Volumetric Water Content .40 .50 0_ .10 .20 .30 .40 .50 y F I I j T 1 EL_ A21 A22 G) 0d . )- Al6d L A17d @30d o33d VSld V53d PE = 0.76 cm/day PE = 0.43 cm/day " O 0 PE = 0.76 cm/day ’ _ A PE = 0.43 cm/day s ’4 ’A .9fflflr . ’ [,é;?' a /’A’./ ar’.// . 9 ,{//' 6 /_// [A 6 / /’ 9 )- / ,’ A / I, l/ //A’ 1( » b / ‘ 0 /! / _.,A // // ”””” !{ )O-FH r, g c // : / ” r ’ . ’ / /% e /// '1 fl // b / / A’ ’4’ 0 / ’I” III’ . l l l l I 4 l I l 10 20 30 40 50 Time-days 12. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core B-5, MOR HUMUS TYPE. 58 Volumetric Water Content 0 .10 .20 .30 .40 .40 .50 I I ‘I r I l 5. 10h E 2’ fi - a. 15 o O 0 0d ‘ 20' Al6d P Al7d a30d E133d VSld V53d 25L ‘ PE = 0.76 cm/day PE = 0.43 cm/day .8- , O PE = 0.76 cm/day s A PE = 0.43 cm/day , 7 b O O . ".1 '1 4.) g o 8" 06 - A m 6 ,93’ > /,/' m .5r 9 /1¥;/. 7'. Af/ 8 a fi(,i)/ .3 .4 " 6 ;/ K o E a g/ ,z”A 03 P , / I’l” .— m , ‘//y 5"; , 0 10 cm 6 A/ ,,/ of] 'I C‘7 /’II t; .2 " '1 ‘ / A’/ '3 /// v 4" O-FH g .1 " o //// [A— ———————— A' ___________ ‘A U n // /// ’4’! L 1 I I I I I I 1 l 0 10 20 30 40 50 Time-days Figure 13. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core C-5, MOR HUMUS TYPE. 59 Volumetric Water Content 0 .10 .20 .30 .40 I I I I 5. 10. E ‘3 fi 15» Q 0 0d “‘ 0 0d 8 Al6d Ale 20% B30d - B33d VSld V53d 25 . L PE = 0.76 cm/day PE = 0.43 cm/day 8 _ O (3 PE = 0.76 cm/day , A PE = 0.43 c d ’ g 57- m/ ay 6 I} ’ /"”A”A m c ,It' 3 .6" ",J¥;" 3wA % a /’j'/”/”’0‘10 cm > 5. ° ’4' ' I” m . I a A,.. H . . g I / / ’9 A O .4 . 1 // o. I, "I' 13' . //f’/ ,4?” O-FH 8 ' , ,/ I: '3 P o //A’// // A’ A G) / / > t // /o // .,.| .2 I [A / A U / // / m x / / , H , / , :3 ’ / // 5 .1 ' K // U n //;/ , I L l l 4 l I l I 1 0 10 20 -30 40 50 Time-days Figure 14. Cumulative fractional evaporation and water con— tent profiles at each potential evaporation for core D-5, PSEUDO DUFF-MULL (MOR) HUMUS TYPE. 60 Volumetric Water Content o .10 .20 .30 .40 .50 .60 o .10 .20 .30 .40 .50 .60 I I I 7 l I ' U f V F ‘_‘_ F V" v 7 ‘I II 0) CH- 5 b ‘ A 7. I.” 11 I) As \\ _ A S 10 "I. 0 12 f) n .. 0 “—- m 15 P Q) n a D H 0 0 0d 0 0d 20 _ ‘ A16d _ Al7d 930d @33d V51d V53d 25 L - PE = 0.76 cm/day PE = 0.43 cm/day .8 - O PE = 0.76 cm/day A PE = 0.43 cm/day c; .7 b o H 4.) {3 .6 - 0 Q: o m E. .5 - . a e g c .3 '4 c ,£Y’A 3 , ,M. “3 3 - ’ ,I/Af/ I): o a 1 7A? a g a ,A’é. 0-10 cm qfl .2 I- 9 X ’ ’f””A U A’/ .. ”___,.—— m e by’ lak” = H , ,,” g l _ 6 IA, " .———"‘"" = ’’’’’’ A r’ K ’7” 5 ————————— -'A—- '''' — ['13 ’1’, 1 I L 1 I I l l I l 0 10 20 30 40 50 Time-days Figure 15. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core F-4, DUFF-MULL HUMUS TYPE. 10 15 Depth—cm 20 25 Cumulative Fractional Evaporation 61 Volumetric Water Content .10 .20 .30 .40 .50 o I U r 1 I -F— 31. A11- A12" B3Od V51d PE = 0.76 cm/day 0.76 cm/day 0.43 cm/day O 'U (:11 II II 0 \\ Time-days Figure 16. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core G-5, DUFF-MULL HUMUS TYPE. 62 Volumetric Water Content 0 .10 .20 .30 .40 .50 0 .10 .20 .30 .40 .50 f l I I I .F— T I I I I All 5- ——r A 12 {'5 10) t c ‘5. m 15' ' 0 <3 0d O 0d 20 _ A16d - Al7d EJ30d 833d VSld V53d 25 PE = 0.76 cm/day — PE = 0.43 cm/day .8- 0 PE = 0.76 cm/day : A PE = 0.43 cm/day O 0.7F -H 4) S O .6 . o o. “3 c a: = A ,_| .6~ : A"/.ér m ’ .—;fr:>”” § 4 " ///A’/ u ° ' 6 ° ‘,a”% g 6 ‘/,Ar 0~10 cm H K .fi m .3. a / ,I’ /A’ ’I” 9 g o / ’,,’ -.-| A/ /A' ’A U .2 - r, // ’ ' ””””” 2 /A [A”” 5 a a fif /“ " 0-5 cm g 01 P / e"- v 1’ ,/ 0 10 20 30 40 50 Time-days Figure 17. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core E-4, MULL WITH F HORIZON HUMUS TYPE. 63 Volumetric Water Content 0 .10 .20 .30 .40 .50 0 .10 .20 .30 .40 .50 I 1 Y I 1 F T I I j I A 5_ 11_ 53 10h- A12- ‘3 .5 Q1 15. n m 9 0 0d 0 0d 20? A16d r Al7d a30d B33d V51d V53d 25L . PE = 0.76 cm/day PE = 0.43 cm/day 08 P O PE = 0.76 cm/day A PE = 0.43 cm/day a o 07 b -H 4J m 8 .6 b a Q: m > c m 05 ' f f; . 8 4 ., sac/A “I". o " // (U 5 /// a _ I: .3 _ a //.B’/- :10 cm a /./ I, g 6 ’A”- / I O .H A ’,. 0—5 cm 4., .2 " O K/ / IA '13 r 3’ "’K/ IIIIII 9 I A/’ z””,A””’ S .1- ,. A’ 3, ,: ..... C) , ,AK ’,,ZA’ 1’ /// 5;; J, I I 1 1 I 1 ‘ A l o 10 If f0 40 50 Time—days Figure 18. Cumulative fractional evaporation and water con— tent profiles at each potential evaporation for core H-4, MULL WITH F HORIZON HUMUS TYPE. 64 Volumetric Water Content 0 .10 .20 .30 .40 .50 0 .10 .20 .30 .40 .50 I r I I W 'F— I I I I I 5- :- A11 E 10- - (I) . ‘3 A12 4.) .- 8' 15L 9 . O 0d A16d Al7d 20F E130d I a33d V51d V53d 25L . PE = 0.76 cm/day PE = 0.43 cm/day 08 P O PE = 0.76 cm/day A PE = 0.43 cm/day c .7b 0 :3 9 m H .6 " c 0 e 53* . A c .A’ El .5 b 9 A/’A’;/ a .,<:>’ '8 9 ;§A// / Q .4 f 6 /- :3 x! ,1 o 6 /K ,,” TU / I: ,i” 0’10 cm a .3 . /g' /£r" '1 0 fi( .x// > 2 _ / 6 // —-_.-______;-£-A :3 ' 0 ,° ,,’A 0—5 cm ‘6 A/ 6 // // PI / / /,I g .1 b 'l / //A/ // ,v / U 6 // ’A/ 0. // ’.—-"' l/l’f'”n I l l A A I l l l 0 10 20 30 40 50 Time-days Figure 19. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core K-5, MULL WITH F HORIZON HUMUS TYPE. 65 Volumetric Water Content 0 .10 .20 .30 .40 .50 .60 0 .10 .20 .30 .40 .50 .60 5? All? 8 10L ___ . 3’ .c 4.) 84 15* ' D 0 0d A12 9 0d. _ ' AlGd _ A17d 20 [330d a33d vsld v53d . L 25 PE = 0.76 cm/day PE = 0.43 cm/day .8 P 0 PE = 0.76 cm/day c :7. A PE = 0.43 cm/day o -H 13’ H .6 b 0 §* 5 m .5 n ' Fl 5 2,46 3 5 2A,}!- O 04 ID 5 ’,’)( .H ,39’ u c é“ 0 e 43”” S 3 L " /A/ a) 5 / 0A 3 2 3/K I”’ g P 0/A 5 ,I’II ’:A H K’ ' él’ ”” ()5cm :3 I, p ..—-- ’I’ - 5 '1r' / /’”(4¢¢!éir ————————— A’ U "/1 ’l”’ O 10 20 30 4O 50 Time-days Figure 20. Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core A-4, MULL HUMUS TYPE. Depth-cm Cumulative Fractional Evaporation 66 Volumetric Water Content O .10 .20 .30 .40 .50 0 .40 .50 0 0d 0 0d Al6d A17d BBOd B33d L V51d L V53d 25 PE = 0.76 cm/day PE = 0.43 cm/day .8P 0 PE = 0.76 cm/day A PE = 0.43 cm/day .7' .6' o .5" e ‘ Ala/3A : ,EA" ” . 745/ .4' 6 '/A’/K/ 5 AW’ '4 /’A/ .3' 9 a/fl/ ””,,,2A a / ‘/ a, t ’J" 0-10 cm .2! e ,z” o f! A” ____::O—A / /e ,,”A——— /' ,H’—- 0-5 cm 1% Al // /A——-"” . 0/ / // / // //;/’ 0 10 20 30 4O 50 Figure 21. Time-days Cumulative fractional evaporation and water con- tent profiles at each potential evaporation for core M-4, MULL HUMUS TYPE. 67 fractional evaporation for each core, and averages for each site as a function of time and potential evaporation are presented in Appendix I. Volumetric water contents as a function of depth and time and bulk density as a function of depth, both determined by gamma attenuation, are pre- sented in Appendix II for each core. Cumulative evaporation For every sample included in this study the cumula- tive fractional loss at any time t > 0 at the high potential evaporation (0.76 cm/day) was greater than that at the low potential evaporation (0.43 cm/day). The classical initial stage of constant rate evaporation equal to the potential evaporation is not evident in these data and probably lasted only several hours. It is observed in several sam- ples, most notably K-S (Figure 19) that a constant rate period extended for several days but at approximately 0.2 cm/day the evaporation is far below the potential evapora- tion of 0.76 cm/day. For the mull humus types (Figures 17 through 21) the rate of fractional evaporation generally decreases more rapidly after 30 days at the low potential evapora- tion than at the high potential evaporation. To a lesser extent this is generally true for the mor and duff—mull types (Figures 11 through 16). This is a departure from the type of curves associated with the drying of bare soil. W. R. Gardner and Hillel (1962), studying the evaporation 68 from bare soils at various potential evaporations, indicate that at sufficiently long periods of time the cumulative evaporation will be the same regardless of the potential evaporation. This same result might be expected for the humus-soil cores at very long times, perhaps two‘ to three- times longer than the approximate 50 days which these results represent. Although there was a considerable difference between humus types in the total water retained at 40-mb tension and the fractional evaporation, the difference in depth of water lost by evaporation between the two potential evaporations was small and showed little variation with humus type. This data is tabulated in Table 4 for the representative cores and in Table 5 as an average for all cores from each sample site. The difference in loss between the two potential evaporations for the averaged data in Table 5 ranged from 0.6- to 1.2-cm, averaging approximately 0.9-cm. Except for sample B-2 (the well-developed root mor) and the duff—mulls, the difference in loss due to potential evaporation was ap— proximately the same for both mulls and mors. However, this difference for all humus types represents less than 0.02 g/cm3 water content. The data of Table 4 and 5 indicates that the total depth of water retained at 40-mb tension is less for the mors (except B-2) than the mulls and duff-mulls. This re- flects the improvement of soil structure associated with mulls and duff-mulls due to increased faunal activity and 69 mmo. m.o vom. m.m m.n 5mm. m.v v.5 VIE Has: omo. o.H mme. m.v m.m mvm. m.m o.oa vu¢ Has: mHH. m.o mmm. ¢.m m.m new. ~.¢ m.m mum Ex: Has: mma. H.H mmv. m.m m.m mmm. m.m o.w elm m\3 Hans vmo. >.o 0mm. ~.m N.m vam. m.m v.m vim m\3 Has: ham. m.H mmv. h.m m.m who. m.v m.m mum Haszlmmso oma. o.a mmm. m.m w.m ovm. m.m h.o vim Hasslmmso sea. m.o owe. H.m ~.m mom. h.~ m.m mun -mmmmvowwme vow. m.o mum. H.N m.m th. o.m m.m mlu no: mHH. m.o Hum. m.m m.v man. >.m n.v mum H02 mma. v.H mom. o.m m.m omm. v.v v.o mum no: 80 EU 80 80 EU EU .mm>m .mm>m .mm>m .mm>m HmwuHsH .mm>m .mw>m HMHuHGH muoo mama mdfidm .omum amuoe .omum Hmuoa .omum Hmuoa Imuflm Hmuoa Hmuoa Hopoe mocmumMMHa mmwxso m¢.o n ma mmu\so ma.o n mm .muoo m>fiumucmmwummu comm no“ coaumnomm>o Hmwosmuom cw mmsmco 0» map mmocmnmmmwv paw .GOHumuomm>m HMGOfluomnm Hmuou .coflumuomm>m Hmuou .ucmusoo umum3 HMHufiGH .w magma 7O .vIU mosaoca uoc moon mmmuw>¢ .mlm mosaosw uoc moop mmmum>¢ m a sac. m.o omm. o.¢ m.n has. m.v v.5 2 Has: mac. m.o Ame. ~.¢ m.m oem. H.m ¢.m a Haas HHH. n.o wow. ~.m o.m mam. m.m m.m x m\3 Has: mNH. m.o «mm. H.m m.m Ham. m.m n.m m m\3 Hans baa. m.o mom. m.m o.s cam. s.s H.n m m\3 Has: mma. o.H “we. o.m m.m mmm. o.v v.m u Hasznmmso mma. N.H mam. m.~ m.m mam. m.m m.m m assaummso mod. a.o man. o.m m.~ mam. a.m o.m a uwmmmvowmwwm NmH. o.H Ham. m.~ m.m man. m.m N.¢ No no: mma. m.o has. a.m m.¢ mmh. m.m «.s Hm no: 80 EU EU EU E0 EU .mw>m .mm>m .mw>m .mm>m amapwsH .mw>m .mw>m HMHUflGH mnou mums mdfidm .omum Hmuoa .omum Hmuoa .omuh Hmuoa .muflm Hmuoe Hmuoa Hmuoa moamumMMHo amnxso m¢.o u mm mmn\so oh.o u mm o®flflm 30mm HON coflumuomm>o Hmwpcmuom cw mmsmso on map moosmummmwp cam .soaumnomm>m HmcoHuomum Hmuou .cowumuomm>m Hmuou .unmgcoo Hmum3 Hmwyflcfl momHm>¢ .m manna 71 incorporation of organic matter. The organic matter not only improves aggregation, particularly in sands by cemeta- tion (Baver, 1956), but also absorbs and retains water. A good example of this is mor sample C and mull sample H (Tables 4 and 5), both developed on Blue Lake sand. The depth of organic matter is greater for the mor than the mull but probably due to improved structure and incorporated organic matter the mull retains about 1.5-cm more water than the mor at 40—mb tension. In the case of sample B-2, the well-developed root mor, the thickness and water hold— ing capacity of the H horizon contributed to this sample's capacity to retain more water (Table 4). The data in Tables 4 and 5 also indicate that mors, including the root mor B-2, lose a greater fraction of the total water in the core than either duff-mulls or mulls. However, the water remaining in the mulls and duff-mulls at the end of both the experiments (51 and 53 days) was greater than that in the mors. Any mulching effect due to thicker organic matter accumulations in the mors is not ap- parent from this phase of the study. In summary, the mors retain less water after satura- tion and lose a greater fraction of this water by evaporation than do either mulls or duff-mulls. The total loss, in terms of actual depth of water evaporated, is generally greater at both potential evaporations for mulls and duff-mulls. During the low potential evaporation experiment a temporary failure of the humidity controls in the environment 72 chamber at 30 days caused the relative humidity to drOp from 70 to 30 per cent, increasing the potential evaporation. This situation continued for two days. As shown in Figures 11 through 21 the rate of evaporation increased for all samples and decreased thereafter until the normal rate was reached at approximately 45-48 days. This has several im- plications. If the evaporation is a true falling rate drying process as defined for a bare soil only the water transmitting properties of the soil control the rate of evaporation and not the atmospheric conditions.- Thus, the criteria of the falling rate stage of drying for bare soils appears to fail for these humus-soil complexes. The rate of evaporation for the mulls without an F horizon, samples, A and M (Figures 20 and 21) changed only slightly and much less than the other samples due to the increased potential evaporation. This is to be expected since these two mulls most closely represent a bare soil. The total loss at 53 days appears to be the same. whether the change in potential evaporation had occurred or not. W. R. Gardner and Hillel (1962) report similar results for bare soil when covered to prevent evaporation. After the cover was removed the evaporation rate increased until the total corresponded with that of a sample not covered.) At any time thereafter the total loss and evapora- tion rate were the same for both samples.. Gardner and Hillel (1962), also report that the addition of a small 73 quantity of water to the soil results in an increased evaporation rate until the quantity added is lost and then the evaporation rate returns to the rate associated with that time had water not been added. The total loss is in- creased by the amount of water added. Although the work of Gardner and Hillel (1962) does not cover the same situa- tion experienced in the humus-soil cores where an increased evaporation rate occurred due to an increased potential evaporation, it appears that similar mechanisms of water movement and evaporation within the soil are involved. Water content-depth profiles Several observations are common to all the water content-depth profiles as a function of time and potential evaporation as shown in Figures 11 through 21. The consid- erable heterogeneity of the humus-soil cores is reflected in the variation in initial water contents (t = 0) between and within horizons. Also noted is the uniform change in water content with depth during a specified time interval, particularly at the lower depths and regardless of the dif- ferences in initial water content with depth. In most cases the loss below lO-cm depth was decreasing uniformly as a function of time. Another observation is that the apparent water loss is the same for both potential evaporations, not only in the horizons above lO-cm but also below this depth. This is due in part to the small differences in evaporation 74 loss at the two potential evaporations. A difference of 1.0-cm in total evaporation is only 0.04 g/cm3 water con— tent. When this difference in loss is distributed over the time intervals of water content measurement and depth of the core it is generally less at any point than the precision and accuracy of the gamma attenuation instru— mentation. Surface water contents were lower during the low potential evaporation than during the high potential evap- oration experiment. It is noted that the initial water content was less in almost every case at the low potential evaporation and this trend continued during the period of evaporation. This demonstrates the resistance to wetting or hydrOphobic nature of dry organic matter. Although the cores were saturated in the same manner before each experi- ment, the organic matter was probably drier after the high potential evaporation experiment than it was when collected in the field and initially saturated. Water content measurements permitted an analysis of the relative water loss from the surface layers of the cores. This is accomplished by integrating between water content curves for the desired time interval and depth. The integration procedure was accurately and quickly com- pleted by cutting the areas to be integrated from graphs and weighing. This method permitted more flexibility than numerical methods since profiles could be drawn freely between points of water content measurement to adjust for soil heterogeneity. 75 The results of the above analysis for the repre— sentative cores at both potential evaporations are shown in Figures 11 through 21 as part of the cumulative frac— tional evaporation with time curves. These curves show the average rate of evaporation and cumulative fractional evaporation at the time of water content measurement for the combined F and H horizons (O-FH in the Figures) and total upper 10-cm layer (0-10 cm in the Figures) for the mors and duff—mulls, and the 0- to S—cm and total upper lO-cm layer for the mulls. It is quite apparent from Figures 11 through 21 that the total fractional evaporation for the upper 10-cm depth is quite similar for both potential evaporations in each representative core and what differences do exist represent little water. For instance, the total loss in the upper lO-cm of core B-5 is 1.9-cm water at the high potential evaporation and 2.0-cm at the low potential evaporation, a difference of only 0.1-cm (Table 6). Be— cause of the small differences in evaporation loss at both potential evaporations, the difference in quantity of water lost in the upper lO-cm may represent only 0.01 to 0.03 g/cm3 water content which is within the approximate precision and accuracy of the gamma attenuation instrumenta- tion used. Thus, to show any real differences in loss of 'water within various layers due to a change in potential evaporation the differences must be greater than those .mnummc oaum can muo 00 sum .cummo Sonoa on momuusm .summu sonoa op um uOHIo uOHIm .mummmH oarmm can mmlo mo Edm .nummp Houoa ou mUMMHSm “OHIO .cumwo Ecloa ou coNHuon mm pmcwnsoo mo Eouuon “caumh 76 mmn\so m¢.o mm mmc\so mn.o mm .npmmp Eoum ou mOMMHSm tom .coNflHoa mm Umcwnfioo mo Eouuon ou oommusm “mmlo H H.m mum. moa. moa. H.~ omm. mmo. mma. «-2 Has: m.~ mmm. moo. nma. v.~ mmm. moo. and. «.4 Has: m.~ omm. «ma. emu. v.m mum. mma. mmm. mum m\3 Has: G.H mam. hmo. HmH. o.~ mmm. mmo. omm. esm m\3 Has: m.a mam. «mo. mam. m.H mmm. Goa. and. sum m\3 Haas oaao oauo oaum mno oauo oauo calm mmuo G.H Hmm. aha. moa. m.H mmm. NNH. FHH.W mum Hasznmmso ¢.H wom. Hoa. mos. m.H mom. sma. mmH. sum Haszummso m.H mmm. mma. 5N4. m.H mmm. spa. nos. mun -memvowwmmE N.H mqm. Gmm. boa. v.a «mm. com. smH._ muo no: o.m was. mom. Nam. m.H Gas. Has. mm~., mum no: EU EU @wmmm oauo calms mmuo owmmm oauo oaumm mmuo -Mmmw mama msssm Hmuoa .mm>m HMGOHuomnm Hmuoe .mm>m HMcOHuomum . .mnoo m>aumucmmmummn comm MOM msoHHMHomm>m Howucmuom anon um EUIQH ovumusm may scum cofiumuomm>m Hmuou can coaumnomm>m Hmcoflpomum Hmuoa .m magma 77 experienced. This does not detract from the usefulness of the data in determining relative rates of loss or relative loss from layers within the cores. The cumulative fractional evaporation for 16 days at the high potential evaporation is greater than that at the low potential evaporation for all representative cores (except D-5, Figure 14) and the differences in most cases should be considered real. This indicates that at the higher potential evaporation the initial rate of loss within the surface layers is greater than that at the lower potential evaporation. The total cumulative fractional evaporation for mulls from the O- to 5-cm depth is generally about twice that of the 5- to lO-cm depth (Table 6). The loss in the mors from the combined F and H horizons is about equal to that from the mineral soil surface to the lO-cm depth. In the well-developed root mor, core B-2, the major loss occurred in the H horizon with only small losses in the underlying 5.3-cm of mineral soil to a total depth of lS—cm (Table 7). The data in Table 6 indicate that generally the total loss of water from the upper lO-cm in each humus type, in terms of depth of water evaporated, is independent of the initial total water content. Although the mors generally have a greater cumulative fractional evaporation in the upper lO-cm, the total loss in terms of depth of water is similar to that lost in the mulls and duff—mulls. 78 .npmwc Eouma 0» mommusm "mane .cummc Hound ou coNfiuoc m mo Eouuon “manm .coNHuoc m “3 sh .coNHHoc m “m no a h.~ Nov. Nmo. mum. Hoa. m.m mom. mho. Hem. mmo. Eu EU male male malm mum mlo malo mHIo malm mum Hmlo .mm>m .mm>m Hmuoa coflumuomm>m HMQOHuomnm Hopes coawmuomm>m Hmcowuomnm smc\so m¢.o u mm smoxso ma.o u mm .mlm muoo .mmwu moans Hoe uoou How ms0flumuomm>m Hafiucmuom anon um Eclma mommusm may Eoum coaumuomm>w Hmuou can cowumnomm>o Hmcowuomum Hmuoa .h magma 79 It is interesting to note in core B-2 (Figure 11), the well-developed root mor, that sometime between 16 and 30 days evaporation from the F horizon ceased for both potential evaporations. This no doubt occurred in the other samples with an F horizon but was not observed be- cause the surface water content measurement was either below the F horizon or the volume measured included part of another horizon. The evaporation rate from the H hori- zon in core B-2 closely resembles that of the entire core since most of the evaporation loss was from the H. Discussion of unsaturated flow mechanisms as related to evaporation Factors effecting the rate and total evaporation from a humus-soil core can be separated into two groups; intrinsic and extrinsic. Intrinsic factors are those within the humus-soil core and extrinsic factors are those outside and controlled externally. The extrinsic factors are temperature, relative 'humidity or vapor pressure, air turbulence, and radiant energy supplied to the core surface. During each experi- ment the above extrinsic factors were held constant with the exception of relative humidity which was varied be- tween experiments. The intrinsic factors primarily control the trans- Inission of water to the soil surface. Among these factors Imay be listed the heterogeneity of the humus-soil complex, temperature and vapor pressure gradients due to evaporative 80 cooling, initial water content and water content gradient, matric suction gradient, conductivity, diffusivity and specific water capacity variations between non-homogeneous horizons, and column length. Another intrinsic factor possibly affecting transmission of water in the humus hori- zons is the property of most organic matter to shrink and change internal structure with changes in water-content. Assuming that Darcy's law is valid for the flow of water in unsaturated soil, the nonsteady-state flow in one direction is generally expressed ae__ M E“ K" 32 (10) .32. 82 where 6 is the volumetric water content, t is time, 2 is distance, ¢ is the total potential and K is the capillary conductivity expressed in length per unit time when ¢ is expressed in units of head. In an isothermal flow system the potential is primarily due to matric or capillary suction and gravity. The value of K has considerable range and is a function of the matric suction or water content with its maximum value at saturation. For a homogeneous isothermal flow system where a single valued relationship exists between the water con— tent and matric suction the potential can be eliminated from equation (10) by defining the variable diffusivity as 61¢ D(6) = K(6)a—e— = K(9)/C(9) (ll) 81 where the diffusivity D(6), expressed as length squared per unit time, is a function of the water content and C(0) is the specific water capacity, or d6/d¢. When gravity is neglected, C(e) is the lepe of the matric suction-water content curve, dB/dP. A single valued re- lationship between the water content and matric suction exists only for a homogeneous column and when water con- tents are obtained under the same conditions, i.e., during adsorption or desorption. Neglecting gravity and using the relationship of conductivity to diffusivity, the flow equation (10) expressed as a diffusion type equation is CD a _ a as —-5-£(D(e)-é-E (12) 0) ('1' In summary, according to the above theory the iso- thermal flow of water in unsaturated soil is due primarily to the driving force of the matric suction gradient when the gravitational head is small. The water content gradient can be substituted for the matric suction gradient only when the matric suction-water content relationship is single valued, or in other words, when the soil is homo- geneous throughout its depth and is in a complete desorption or adsorption cycle. The above theory is presented for an isothermal flow system. However, cooling during evaporation results in a temperature gradient and may cause a net transfer of soil xvater from warmer to cooler regions (Cary, 1966). Flow 82 due to temperature gradients may be in both vapor and liquid phases with the vapor flow primarily as molecular diffusion. As the water content decreases the relative importance of thermally induced flow increases; liquid flow decreases and vapor flow increases. A change in the temperature gradient will have a greater effect on vapor flux because of the ex- ponential relation of vapor pressure with temperature. Although evaporation from soil is not an isothermal process, it has been shown that the diffusion flow equation (12) adequately describes the major components of flow dur— ing evaporation (Philip, 1957; W. R. Gardner, 1959). This is necessarily true when the soils are initially wet or near saturation. At low water contents the thermal gradi- ents are more important and must be considered. When a homogeneous soil has both uniform initial water content and diffusivity with depth the flux is also uniform with depth at low evaporation rates (W. R. Gardner and Hillel, 1962). Short column lengths and/or high initial water contents will also result in uniform drying with depth (Covey, 1963). Jensen and Klute (1967) demonstrated in small soil columns that during evaporation water will flow against the water content gradient as vapor in response to a thermal gradient. Under isothermal conditions water flowed as a liquid against the water content gradient in response to the matric suction gradient. In either case the water con- tent decreased with depth in a more or less uniform manner. 83 During evaporation from a heterogeneous field soil Hallaire (1958) reports that the water contents of succes- sive soil layers to a depth of 60-cm, although not at the same initial water content, decreased uniformly with depth in response to a suction gradient and not the water content gradient. In fact, flow was generally against the moisture gradient. The matric suction varied with depth in a con- tinuous and regular manner except in the surface layers where greater evaporation loss occurred. This indicates that below the surface layers the water flux is proportional to the matric suction gradient. When evaporation begins from an initially wet or near saturated soil, water flows in response to the suc- tion gradient in both the liquid and vapor phases (Hanks, H. R. Gardner, and Fairbourn, 1967). The vapor flow is restricted to the surface layer.. As the soil dries the magnitude of thermal induced flow increases but the major flux is still in response to the suction gradient. The depth or zone of evaporation has been estimated in a number of ways. H. R. Gardner and Hanks (1966) used heat flux plates and determined that the zone of evapora- tion moved into the soil from the surface at a continuously decreasing rate and the zone in which evaporation took place was about l-cm thick.' This was also confirmed by Fritton, Kirkham, and Shaw (1967) by observing the depth of dry crust deve10pment and salt accumulation. The higher the potential evaporation the deeper the zone of evaporation 84 moved into the soil. Above the zone of evaporation the transfer of water is in the vapor phase, below the zone the transfer is primarily liquid if the soil is sufficiently wet. From this brief outline of water flow in unsatu- rated soil during evaporation, some concepts of flow in the humus-soil cores can be developed. Because the initial and final water contents of the samples used in this study were generally high we can conclude from the earlier dis- cussion that thermal gradients were probably slight and only a small percentage of the net flux was thermally in- duced. Also, any thermal gradients that did develOp were probably quickly altered by heat transfer into the soil through the uninsulated core walls because external con- ditions around the cores were constant. Thus, the following discussion will center on theoretical matric suction gra- dients as developed during evaporation and their relation to observed results. The discussion will apply to the results from both potential evaporations since only small differences in loss occurred. From the water content profiles in Figures 11 through 21 it is evident that for all humus types the ini— tial water content in the surface organic or mineral hori- zons with high organic matter content is greater than that at deeper depths. Since the matric suction was slightly greater at the surface after equilibrium was reached on the tension table, the moisture release characteristics 85 (water content as a function of matric suction) differ from layer to layer reflecting heterogeneity in physical prOperties and density. Although the matric suction gradient is uniform and continuous with depth (except at the surface) and not affected greatly by heterogeneity, the amount of water loss at each depth is determined by the moisture release characteristics of the soil as con- trolled by physical properties. As an example of the forces involved in unsaturated flow within the humus-soil cores the results from a mull will be discussed. For purposes of illustration it will be assumed that the initial matric suction at the surface is equal to that at the bottom when actually there was a slight difference of 25-mb. The initial matric suction P0 as a function of depth is shown in Figure 22. Hypothetical moisture release curves for desorption are presented in Figure 23 for a soil with an upper layer h with incorporated organic matter and a deeper mineral layer :3. Coarse to medium textured soils, containing a quantity of large pores, as in the deeper mineral layer, have characteristic moisture release curves where the greatest amount of water is lost at relatively low suctions. On the other hand, due to highly absorptive organic matter mixed with mineral soil and improved structure the upper layer retains more water at low suctions and loses water less rapidly with an increase in suction. Thus, the initial water contents of the humus layer eho and the mineral soil 86 t Pn P3 P 2P1PO Depth-cm Matric Suction Figure 22. Hypothetical matric suction gradients developed during evaporation as a function of core depth and time. Volumetric Water Content _-———-———- b—-——— th PhlPSZPslPO 0 Matric Suction Figure 23. Hypothetical moisture release curves for a humus horizon, h and mineral soil horizon, s. 87 layer 680 are shown to differ due to the ability of the media to retain water as a function of the matric suction. As evaporation loss from the humus-soil core con- tinues the matric suction gradient becomes steeper as demonstrated by Hallaire (1958). The change in gradient dP/dx is represented in Figure 22 at times t1, t2,...,tn. The matric suction increases in a continuous manner re- gardless of the heterogeneity except at the surface where a larger gradient exists due to develOpment of a dry layer as evaporation progresses. This surface gradient is not shown in Figure 22. Translating the information of matric suction as a function of depth to the moisture release curves in Figure 23 readily explains the water content profiles ob- served during evaporation. As the matric suction increases more rapidly in the upper humus layer it loses more water than does the lower mineral layer. Thus at time t1, (ehl — eho) > (0 - 6 ), and at a later time t2, (6h2 - ehl) > (682 - 6 81 so sl)' This situation continues for any time interval considered during the period of observation. Depending on the moisture release characteristics, these differences in water loss as shown may decrease with time. It may be concluded that the evaporative loss at any time from a heterogeneous soil is a function of the matric suction gradient and its inter- action with the moisture release characteristics as they vary with depth. 88 The same principles advanced above will also apply to the other humus types. In the mors, instead of a gradual change in physical characteristics with depth there is a sharp discontinuity at the H-A2 interface. A series of moisture release curves may be constructed for the organic and mineral horizons leading to results similar to those observed. The actual zone of evaporation in the humus-soil cores is difficult to determine from the water content profiles because of the masking effect of heterogeneity. Differences due to varying the potential evaporation are also masked by heterogeneity and by the small differences in actual water loss as previously discussed. At both potential evaporations the mulls without an F horizon (Figures 20 and 21) generally exhibit a continuous loss of water at the 2- to 3-cm depth indicating that the zone of evaporation was above or within this depth. This depth is similar to that reported by Fritton, §E_al. (1967) for bare soils under a similar potential evaporation. The zone of evaporation in humus types with an F horizon is most certainly below the F horizon and probably within the H horizon when present since it is still losing water at the end of the experiment. The F horizon may exhibit a continual loss of water over a long period of time due to a slower release to evaporation of the absorbed water in twigs and other woody material. The primary zone of evap- oration, the zone where most of the soil water is evaporated, 89 would move into a lower horizon with more continuous smaller pores after the initial water is lost from the F horizon. The F horizon was visually observed to be dry after a few days in most humus types verifying that addi- tional loss was absorbed water. Comparison of humus types by rates of evaporation and diffusivities A comparison of the average cumulative fractional evaporation curves for each site indicates that some simi- larities exist in the general curve shape or change in rate of evaporation with time. Based on these and previously discussed hydrologic properties the humus types can be separated into four groups, each representing a distinct humus condition. The cumulative fractional evaporation curves in Figures 11 through 21, although representative and not an average for each site, nevertheless indicate the general shapes. Differences in shape are more distinct for the average curves of each site. The four basic hydrologic groups, as represented by general humus types, and characteristics of each are: 1. Mulls without F horizon - includes cores A and M (Figures 20 and 21); initial high evaporation rate rapidly changes at approximately seven days to a continuous, gradual falling rate. 2. Mulls with an F horizon — includes cores E, H and K (Figures 17, 18 and 19); initial evaporation 90 rate is somewhat constant for 12 to 20 days, and thereafter decreases at a gradual falling rate. 3. Mors and pseudo duff-mulls - includes cores B, C and D (Figures 11, 12, 13 and 14); evaporation rate is uniformly decreasing for the entire period of evaporation. 4. Duff-mulls - includes cores F and G (Figures 15 and 16); evaporation rate also decreases uniformly with time as with mors but rate of decrease is less. Average diffusivities as a function of the total water content at any time were determined by adapting a pro- cedure presented by W. R. Gardner and Hillel (1962) using a solution of the unsaturated flow equation (12) as outlined by W. R. Gardner (1962). The rate of evaporation is shown to be E = -dW/dt = D(6)Wfl2/4L2 (13) where E is the evaporation rate, 6 is the average water content of the soil obtained by dividing the total water content W by the length L, and D(0) is the known diffusivity function. This assumes an exponential relationship of dif- fusivity and water content first shown to exist by W. R. Gardner (1958) and greatly facilitates the solution of the diffusion flow equation (12) . There is no evidence to sup- port this assumption for all soils, particularly heterogeneous soils. 91 Using equation (13), W. R. Gardner and Hillel (1962) predicted the rate of evaporation at a very high potential evaporation during the falling rate stage from a homogeneous bare soil. Results were then translated to match the end of the initial constant rate stage at lower potential evaporations to predict the corresponding fall— ing rate stage of evaporation. Although all the initial boundary conditions were not met in the humus-soil cores, equation (13) was solved for the diffusivity function A 2 2 D(6) = (-dW/dt)4L /Wn (l4) and average diffusivities as a function of average water contents within the cores were computed. Plots of the computed diffusivities as a function of water content can be separated into four groups by humus type corresponding to those previously discussed. This is to be expected because (-dW/dt), or E, was the primary variable used in separating the evaporation curves into the four hydrologic groups. The results are presented in Figure 24 for one sample from each group. A similar curve exists for all sampling sites included in each group. Re- sults in Figure 24 are for the high potential evaporation; those computed for the low potential evaporation are com- parable but approximately ten per cent lower indicating that boundary conditions were not met. Diffusivities for mulls without an F horizon and duff-mulls approach a somewhat constant value after an 92 o Mull (A) 12_ B.Mull with F horizon (K) 1 V'Duff-mull (G) A Mor (B) 10 r- . - '1 F 3 . 'U \ N 5 r- J I >1 4.) -H > 6 r- - -a m 5 w: m . . a .1 4 I- A d t l' i A . J A 7716‘. AL '1 2- A 4 - '4: r. 4 . 4 L l l l L l l 0 .10 .20 .30 .40 Volumetric Water Content Figure 24. Average diffusivities as a function of water content for representative mull, mull with F horizon, duff-mull, and mor humus types. 93 initial rapid decline at the start of evaporation. In contrast, the mulls with an F horizon and mors show a relative uniform decrease in diffusivity with decrease in water content. These results must be interpreted as due to an interaction of the humus and mineral soil con- stituents and not the humus alone because the diffusi- vities computed are an average for the total core. However, these results do provide a verification of the grouping of humus types by the associated rates of evaporation and suggests a range of diffusivities to expect. Effects of F horizon removal on evaporation To determine the role of the F horizon in evapora- tion one humus-soil core from each sampling site was placed in the environment chamber at the high potential evaporation for 53 days with humus horizons intact. This same procedure was followed for another 53 days after the cores were rewet and the F horizon removed. The result- ing changes in evaporation rate and shape of cumulative evaporation curve were similar for each of the humus samples contained in the four hydrologic groups previously described. These results were presented for one humus- soil core from each hydrologic group in Figures 25 and 26. Complete results for cores before and after F horizon removal, including average depth of the F horizon, are presented in Appendix III. 94 Cumulative Evaporation-cm 10 20 36 4o 50 Time-days F removed Mull with F K-l F horizon 1.4-cm thick Cumulative Evaporation—cm 10 20 30 40 50 Time-days Figure 25. Effect of F horizon removal on cumulative evaporation from mull and mull with F horizon humus types. Cumulative Evaporation-cm Cumulative Evaporation-cm 95 Mor B-l F horizon 2.0-cm thick l l l 10 20 30 40 50 Time-days F in place Duff—Mull G-l F horizon 3.4-cm thick 10 20 30 40 50 Time-days Figure 26. Effect of F horizon removal on cumulative evaporation from mor and duff-mull humus types. 96 Removal of the F horizon had the greatest effect on mulls that originally had an F and duff-mulls. Evapora- tion rates increased during the early stages and later decreased such that total cumulative evaporation at 53 days was similar to that when the F horizon was intact. Because the initial quantity of water retained in the core was less after removal of the F horizon, removal resulted in a greater fractional loss. Removal of the F horizon on the mors resulted in little change in the initial evap- oration rate but the rate generally decreased at later times.. The total cumulative evaporation when the F was removed was less than when the F was intact. Mulls not having an F horizon are represented by core A in Figure 25. This core does show a change in evaporation rate that is probably due to two factors. Un— decomposed debris consisting of leaf petioles and veins and several small twigs, as shown in the photograph Figure 5b, were removed from the surface of the core at the same time the F horizon was removed from the other cores. Al— though only 5-grams in dry weight, these may have been enough to act as a form of stubble mulch keeping the tur- bulent air layer further above the soil surface. A second contributing factor may have been a 0.6-cm lower initial water content at the time the organic matter was removed from the surface. Core M, the other mull similar to core A, had nothing removed from its surface and the evaporation curves were the same during both experiments providing a check on the conditions in the environment chamber. 97 In summary, removal of the F horizon has its greatest effect on mulls and duff-mulls indicating that the F horizon serves a functional role as a mulch even though it initially retains and then later loses water by evaporation. The re- moval of the F horizon from mors has little effect on the initial rate of evaporation. This indicates only slight mulching effect from an F when underlain by a continuous H horizon in contrast with duff-mulls where the H horizon is generally not continuous and contains mineral matter above or intermixed due to faunal activity. Infiltration and redistribution of water Simulated rainfall was applied to a single humus- soil core from each of the ten sampling sites. The intensity of simulated rainfall was 3.0 cm/hour and duration was be— tween 30- and 40-minutes. The initial entrance of water into the core and its subsequent redistribution was fol— lowed by gamma attenuation. Water content measurements were continued'until the wetting front reached the end of the core, generally after 1.5- to 3-hours. The sample from site M, a mull, developed a few surface cracks during the drying period prior to infiltration and therefore yielded erratic and non-representative data. Movement of water into and within the humus-soil cores was rapid due to the coarse textured soils and exhibited little difference between humus types. However, 98 some observations can be made regarding differences in water transmission and retention properties of the humus horizons. Changes in water content as a function of depth and time for three of the nine completed cores are pre- sented inFigure 27. These are a mull (A—3), a mull with F horizon (K-4), and a duff-mull (F-2). Cores A-3 and F-2 received approximately 2-cm of water in 40-minutes and K-2 approximately 1.5-cm in 30-minutes. Average times of water content measurement are noted in Figure 27. Solid lines denote water content profiles during water applica- tion and dashed lines after application ceased. Horizon depths are also noted. A complete tabulation of volumetric water contents as a function of depth and time for each core are presented in Appendix IV. Water advanced into the soil as a wetting front maintaining the non-uniform shape of the initial water con- tent profile except at the surface and end of the wetting front. This phenomena results from the matric suction-water content relationship for absorption varying with the heter— geneous soil. Only after the soil becomes sufficiently wet and water has moved into deeper layers does the water content profile become more uniform with depth.. Core A-3, Figure 27, is a good example of this phenomena. Infiltration and advance of the wetting front were similar in the mulls with and without F horizons, and also similar in the mors and duff-mulls. After entering the 99 .mmmmu mafia: Hawaimmsp cam .m suflz HHDE .HHSE m>apmucmmmummu How mopssflfi cfl mmeu mmmum>m um Hmum3 mo coausnflnumflcmn cam coaumupawmsH Nlm HHSZIMMDO HH [m]. CH om ma OH vim m Suflz HHSS 9 some \\ .1 8mm a axe 2:0 _ x - so 0 __\ a. a” Nam _ _ 2.“. A: \Q 1 HH¢.. Q\ L — L b h] om ma OH O unmucou Hmumz oauumfidao> mtfi Hafiz 1V. Emomb “\ 500 B : Ehm a away 5 1* EC .hm musmflm om mo—qndea 100 soil the wetting front advances in mulls more slowly than in mors and duff-mulls. This is attributed not only to finer soil textures in some mulls but also to incorporated organic matter and improved structure. Although the F horizon was visibly wet during in- filtration, the results from duff-mull F-2 in Figure 27 show the actual water content to increase little during the period of infiltration. This is also true for the H horizon where the water content during infiltration in- creased from 0.31 to 0.34 g/cm3, as compared to the water content at 40-mb tension of approximately.0.50 g/cm3. Apparently in dry organic layers there is a resistance to wetting as previously noted and infiltrating water only wets the organic matter particle surfaces and not the smaller pores. This apparent resistance to wetting was observed in all mor and duff—mull cores except mor B-S. Because of the resistance to wetting, water moves rapidly through the porous organic matter into the under- lying soil. The organic matter does not act as a sponge, at least not during the initial phases of infiltration. It would be expected that for precipitation of long dura- tion, longer than the 30- or 40-minutes used here, more water would be absorbed as the resistance to wetting is re- duced with time. _However, when precipitation beings, dry organic matter layers serve only to break raindrop impact and provide a means of quick transfer to the mineral soil. Little water is initially retained in the organic matter. CHAPTER VII SUMMARY AND CONCLUSIONS The objectives of this study were 1) to determine the hydrologic influence of forest humus on evaporation and the distribution of water within the humus-soil complex during evaporation; 2) to determine the movement of water into and through humus horizons during infiltration and percolation; and 3) to establish a hydrologic basis for the morphological humus types recognized in White's (1965) prOposed humus classification system for the Lake States Region. Ten sampling sites were chosen in the forested regions of Michigan including a variety of soil and forest conditions and the common humus types of mull, duff—mull, and mor. One other humus type common to the Lake States Region, a pseudo-duff-mull was also sampled. Relatively undisturbed samples 16.5-cm in diameter and 25.4-cm deep were excavated from the humus-soil profile and evaporation experiments were conducted in a laboratory environment chamber under controlled conditions of temperature, rela- tive humidity, air turbulence, and radiant energy. By changing the relative humidity, two different evaporation lOl 102 experiments were conducted on the same samples at potential evaporations from a free water surface of 0.76 and 0.43 cm/ day. Average water content changes in 2.5-cm depth incre- ments were determined by the attenuation of a gamma beam transmitted through the humus-soil core. This study supports the hypothesis that soils with biologically incorporated humus, mulls and duff-mulls, are hydrologically different from mors or mors with colloidal infiltration of organic matter (pseudo duff-mulls). The humus types included in this study may be logi- cally separated into four hydrologic groups, each apparently not influenced by the site to site variations in mineral soil characteristics. Although based primarily on the change in rate of evaporation with time during a 51- to 53-day period of constant potential evaporation, other hydrologic prOperties observed during evaporation and in- filtration for each humus type also fit into the four hydrologic groupings. The four groups listed by humus type are l) mulls without an F horizon; 2) mulls with an F hori- zon; 3) mors, including pseudo duff-mulls; and 4) duff- mulls. These four groups consist of humus types as recognized by White (1965) for the Lake States Region with only the additional distinction being made in the mulls for the presence or absence of an F horizon. This distinc— tion is necessary in hydrologic considerations because of the influence of the F horizon on evaporation. 103 For every sample included in this study the cumula- tive evaporation at any time was greater at the high potential evaporation than that at the low potential evapo- ration. An initial constant rate stage of evaporation of several days duration equal to the evaporation from a free water surface as documented in the literature for homogeneous bare soils (Lemon, 1956; Gardner and Hillel, 1962; Fritton, et al., 1967) was not observed in this study. Thus, during the early stages of evaporation the presence of organic matter, either as separate horizons or incorporated with mineral soil, reduced the initial evaporation loss as com— pared with that from bare soil. The falling rate stage of evaporation in the mulls without an F horizon corresponded closely with that des- cribed in the literature for homogeneous bare soils where the rate of evaporation depended primarily on the water transmitting prOperties of the soil and not on atmospheric conditions. In the case of humus types with an organic layer above mineral soil a change to a higher potential evaporation resulted in a significant change in the rate of evaporation. Thus, the presence of organic layers reduce the rate of evaporation to some value lower than the maximum water transmitting properties of the humus-soil complex. Because of the increased organic matter in the mineral soil horizons and its influence on soil structure and water holding capacity, the mulls and duff-mulls held 104 more water after saturation and subsequent drainage at 40-mb tension than the mors. The mors lost by evaporation a greater fraction of the total initial water content-- approximately 80 per cent as compared with approximately 60 per cent for the mulls and duff-mulls at the high poten— tial evaporation. However, since mulls and duff—mulls had a greater water holding capacity, the actual evaporative loss in terms of water depth was generally greater. Results i were similar at the low potential evaporation. The differ— ence in evaporation loss between the two potential evapora- -;'_l _.—.r-.. I .- tions ranged from 0.6- to 1.2—cm with an average of 0.9-cm loss for all humus types. This difference represented approximately 0.04 g/cm3 volumetric water content over the total depth of the core. Water was observed to flow against the humus-soil water content gradient during evaporation in response to an assumed matric suction gradient. Thermal gradients were assumed negligable. The amount of water loss was governed by the matric suction-water content relationships for each horizon as influenced by the organic matter present. The initial water loss was uniform with depth but as the matric suction gradient increased, greater loss occurred near the surface. Below the lO-cm depth the loss was generally uniform with depth and also uniformly decreasing with time for all humus types. Although the total loss at SO-days from the upper lO-cm was approximately the same for both potential evaporations, the loss during the first 16-days 105 was generally greater at the high potential evaporation. As is the case for loss from the total core, mors had a greater fractional loss in the upper 10-cm. However, the actual total water loss in the upper lO-cm was similar for all humus types. The loss from the 4- to 5-cm thick organic horizons in mors and duff-mulls was generally similar to that lost from the first 5-cm of mineral soil. In the mulls the loss from the upper 5-cm was about twice that of the 5- to lO-cm depth. During evaporation the F horizon ceased to lose : significant amounts of water sometime between 16 and 30 days, regardless of the potential evaporation used in this study. However, the H horizon when present continued to lose water at a decreasing rate for the entire period of study. The removal of the F horizon had the greatest ef- fect on evaporation from mulls with an F horizon and duff— mulls. In both groups the initial rate of evaporation was increased, but at 53-days the total loss was approximately the same despite the fact that the total water content of the core was greater when the F was present. The shape of the cumulative evaporation curves, or the changes in rate of evaporation with time, for these two groups after the F horizon was removed resembled that of mulls without an F horizon. Removal of the F horizon from mors had little effect on the rate of evaporation and only a slight effect on the total cumulative evaporation at 53 days. 106 Although there was no direct correlation in change in rate of evaporation with thickness of F horizon removed, there was evidence that a small amount of twigs and unde- composed leaf petioles and veins on the surface of a mull reduced evaporation by providing a thicker layer of non- turbulent air at the soil surface. When a simulated rainfall of 1.5- to 2-cm in 30- to 40-minutes was applied to a humus-Soil core that had been previously dried by evaporation, the water advanced quickly through the soil as a wetting front maintaining the non-uniform shape of the initial water content profile except in the surface layer and at the end of the wetting front. Only after the soil had reached a high water con- tent did the water content profile become more uniform with depth. Infiltration and advance of the wetting front were similar in the mulls with and without F horizons and also similar in the mors and duff-mulls. The rate of wetting front advance was slower in the mulls due to in- creased organic matter in the mineral soil. These results agree with those earlier reported by Trimble, et al. (1951). During simulated rainfall the F and H horizons resisted wetting and water moved rapidly through them into the underlying soil. The actual water content of the F and H horizons increased only slightly as the surfaces of the organic matter particles were wetted and not the smaller pores. Thus, the ability of humus to hold water 107 for later infiltrationas suggested by Trimble and Lull (1956) is not evident in this study. It could be postu- lated that as continued wetting occurs during storms of long duration the resistance to wetting reduces with time and the humus increases in water content. But it is doubtful that humus initially retains large quantities of water if the underlying soil's percolation rate is not exceeded. When the percolation rate is exceeded the humus horizons, because of the high porosity, can hold water and offer a resistance to reduce overland flow. It would be difficult to translate the results of this study to actual quantitative estimates of evaporative loss throughout the year under conditions within the forest. Many factors are involved that were not included in the laboratory study. Under field conditions evapora- tion as well as transpiration losses will occur simul- taneously and because there is generally a high concentra- tion of roots within or near the humus horizons due to greater availability of nutrients and water, the combined losses could considerably alter the quantitative results of this study. In the field there are also varying con— ditions of potential evaporation as related to wind, humidity, temperature, and radiation and their diurnal and seasonal fluctuations. Repeated wetting and drying, as affected by hysteresis and diurnal temperature changes within the longer natural soil profile will result in 108 conditions different from those in the laboratory and consequently result in different rates of evaporation. During a period of evaporation under field conditions there is usually a downward movement of water in unsatu- rated soil in response to gravity, much more so than that which occurred in the laboratory samples where effects of gravity are negligible. It is expected that the downward movement of water in the field will remove water from the surface layers and will result in a reduced evaporation loss as compared with the loss at the same potential evaporation in the laboratory. Although these results cannot be used for quanti- tative field estimates, the results do indicate the relative differences in hydrologic properties between humus types from one geographical region and their rela- tion to a proposed humus classification system. Hydrologic prOperties alone cannot be used to classify humus and mor- phologic characteristics and degree of biological activity as proposed by White (1965) must still be used as a practi- cal basis for field classification. However, hydrologic properties parallel the humus classification system and support the validity of the distinct types as found in the Lake States Region. The results of this study provide a basis for additional investigation in two general areas. One study 'would be a detailed investigation of several samples similar 109 to those used in this study where not only water content but matric suction and temperature are also measured throughout the sample depth. Thisis not a simple task because non-destructive placement of tensiometers and temperature sensors is difficult. There is also the prob- 1em of keeping continuous contact between the tensiometer and humus as the humus shrinks during drying. If these problems can be solved, the validity of the unsaturated soil flow equations may be tested for the non-homogeneous system and the magnitude and direction of vapor and liquid ‘w flow in response to temperature and suction gradients can be determined. If the effects of different potential evaporations are desired in a future study, the differences between potential evaporations must be greater than the 0.33 cm/day used in this study. A greater difference can be achieved by varying the temperature and radiation input as well as relative humidity. Another area in which the results of this study would be useful is the establishment of field plot studies to determine the actual role of the various humus types in the forest hydrologic cycle.2 The gamma attenuation in- strumentation used in this study to measure water contents proved successful under laboratory conditions and based on 2A preliminary field investigation was originally included as part of this study's objectives but was can— celled when the gamma attenuation instrument was lost and damaged during shipment at the beginning of the field season and not returned in operating condition for several months. 110 results of field measurements of snow and sediment density (Smith, Willen, and Owens, 1965; McHenry and Dendy, 1964) could be used in the field to measure water contents after careful calibration. Temperature sensitivity of the de- tector photomultiplier tube and difficulty in determining actual volumetric water contents to serve as a point of reference at the beginning are problems which must be over- come before this instrumentation can be successful in the field. This latter problem is reduced somewhat if rela- tive volumetric water contents will meet the objectives of the field investigation. Water contents as determined by gamma attenuation and related matric suctions at each depth increment on controlled field plots can provide estimates of evapora- tion, transpiration, and downward movement. Results of this type will only be estimates until the problems pre- sented by continuous wetting and drying and hysteresis can be solved. In a slowly changing system as found in the field, however, it may be possible to use an average soil water conductivity or diffusivity for each distinct homogeneous layer to represent the unsaturated flow in light of the other problems presented by heterogeneity and non-uniform removal of water by plant roots in the soil profile. Adams, J. E., 1957. Arend, J. L. 1941. LITERATURE CITED D. Kirkham and D. R. Nielsen A portable rainfall-simulator infiltrometer , and physical measurements of soil in place. {—7 Soil Sci. Soc. Amer. Proc. 21:473-477. Infiltration rates of forest soils in the Missouri Ozarks as affected by woods burning and litter removal. J. For. 39:726-728. Army, To J. I A. F. Wiese, and R. J. Hanks ”"4“" 1961. Baver, L. D. 1956. Benoit, G. 1963. Blow, F. E. 1955. Cary, J.W. 1966. Covey, W. 1963. R. Ferguson, H. ‘1962. Effect of tillage and chemical weed control practices on soil moisture losses during the fallow period. Soil Sci. Soc. Amer. Proc. 25:410-413. Soil physics. John Wiley and Sons, Inc., New York. 3rd edition. 489 pp. and D. Kirkham. The effect of soil surface conditions on evaporation of soil water. Soil Sci. Soc. Amer. Proc. 27:495-498. Quantity and hydrologic characteristics of litter under upland oak forests in eastern Tennessee. J. For. 53:140-195. Soil moisture transport due to thermal gradients. Soil Sci. Soc. Amer. Proc. 30:428-433. Mathematical study of the first stage of drying Of a moist SOil. Soil Sci. Soc. Amer. Proc. 27:130-134. and W. H. Gardner Water content measurement in soil columns by gamma ray absorption. Soil Sci.Soc. Amer. Proc. 26:11-14. 111 Fritton, D. 1967. Gardner, H. 1966. Gardner, W. 1965. Gardner, W. 1958. Gardner, W. 1959. Gardner, W. 1962. Gardner, W. 1962. C. G. 1962. Gurr, Hallaire, M. 1958. 112 D., D. Kirkham, and R. H. Shaw Soil water and chloride redistribution under various evaporation potentials. Soil Sci. Soc. Amer. Proc. 31:599-603. and R. J. Hanks Evaluation of the evaporation zone in soil by measurement of heat flux. Soil Sci. Soc. Amer. Proc. 30:425-428. R. H. Water content, p. 82-127. 31. (ed.) Methods of soil afialysis. Agronomy Monograph No. 9. Amer. Soc. Madison, Wisconsin. In C. A. Black et Part-I, Agron., R. Mathematics of isothermal water conduction in unsaturated soil. p. 78-87. 32.3“ F. Winterkorn (ed.) Water and its conduction in soils. National Academy of Science, National Research Publication 629. Washington, D.C. R. Solutions of the flow equation for the drying of soils and other porous media. Soil Sci. Soc. Amer. Proc. 23:183-187. R. Note on the separation and solution of dif- fusion type equations. Soil Sci. Soc. Amer. Proc. 26:404. and D. I. Hillel The relation of external evaporation condi- tions to the drying of soils. J. Geophysical Research 67:4319-4325. R. Use of gamma rays in measuring water content and premeability in unsaturated columns of soil. Soil Sci. 94:224-229. Soil water movement in the film and vapor phase under the influence of evapotranspira- tion. p. 88—105. In H. F. Winterkorn (ed.) Water and its condEEtion in soils. National Academy of Science, National Research Publi- cation 629. Washington, D.C. Hanks, 1967. R. J. 1958. Hanks, Helvey, J. D. 1964. Hide, J.C. 1954. Hoover, M. D. 1952. Jensen, R. D. 1967. Kittredge, J. 1948. E.R. 1956. Lemon, R. J., H. R. Gardner, 113 and M. L. Fairbourn Evaporation of water from soils as influenced by drying with wind or radiation. Soil Sci. Soc. Amer. Proc. 31:593-598. and N. P. Woodruff Influence of wind on water vapor transfer through soil, gravel, and straw mulches. Soil Sci. 86:160-164. Rainfall interception by hardwood forest litter in the southern Appalachians. U.S. Forest Service Research Paper SE-8. 9 pp. Observations on factors influencing the evaporation of soil moisture. Soil Sci. Amer. Proc. 18:234-239. Soc. and H. A. Lunt A key for the classification of forest humus types. Soil Sci. Soc. Amer. Proc. 16:368—370. and A. Klute. Water flow in an unsaturated soil with a step-type initial water content distribution. Soil Sci. Soc. Amer. Proc. 31:289-296. Forest influences. McGraw-Hill Book Co., Inc., New York, 394 pp. The potentialities for decreasing soil mois- ture evaporation loss. Soil Sci. Soc. Amer. Proc. 20:120-125. Lowdermilk, W. C. 1930. Influence of forest litter on runoff, per- colation, and erosion. J. For. 28:474-491. McHenry, J., and F. E. Dendy 1964. Metz, L. J. 1958. Philip, J. R. 1957. Moisture held in pine litter. J. For. Measurement of sediment density by attenua- tion of transmitted gamma rays. Soil Sci. Soc. Amer. Proc. 28:817-822. 56:36. Evaporation and moisture and heat fields in the soil. J. Meteorology 14:354-366. 114 Reginato, R. J., and C. H. M. van Bavel 1964. Soil water measurement with gamma attenua- tion. Soil Sci. Soc. Amer. Proc. 28:721-724. Rowe, P.B. 1955. Effect of the forest floor on disposition of rainfall in pine stands. J. For. 53:342-348. Russel, J. C. 1939. The effect of surface cover on soil moisture losses by evaporation. Soil Sci. Soc. Amer. _ Proc. 4:65-71. . ‘P“1 Smith, J.L., D. W. Willen, and M. S. Owens. 1965. Measurement of snowpack profiles with radio- active isotopes.. Weatherwise 18:247-251. 1 Thames, J. L. 1966. Flow of water under transient conditions in unsaturated soils. Ph.D. Dissertation, g y Dept. of Watershed Management, University of Arizona. Trimble, G. R. and H. W. Lull 1956. The role of forest humus in watershed manage- ment in New England. U.S. Forest Service, N.E. Forest Exp. Sta. Paper 85. 34pp. Trimble, G. R., E. E. Hale, and H. S. Potter 1951. Effects of soil and cover conditions on soil- water relationships. U.S. Forest Service, N.E. Forest Exp. Sta. Paper 39, 44 pp. van Bavel, C. H. M. 1959. Soil densitometry by gamma transmission. Soil Sci. 87:50-58. van Bavel, C. H. M., N. Underwood, and S. R. Ragar 1957. Transmission of gamma radiation by soils and soil densitometry. Soil Sci. Soc. Amer. Proc. 21:588-591. White, D. P. 1965. The classification of upland forest humus types in the northern Lake States Region. Unpublished File Report, Department of Forestry, Michigan State University and Div. of Watershed Mgt., N. Central Forest Exp. Sta., U.S. Forest Service. 34 pp. 115 Wilde] Svo 1958. Forest soils. Ronald Press, New York. 537 pp. Wilde, S. A. 1966. A new systematic terminology of forest humus layers. Soil. Sci. 101:403-407. APPENDIX APPENDIX I. POTENTIAL EVAPORATION = 117 CUMULATIVE AND CUMULATIVE FRACTIONAL EVAPORATION AS A FUNCTION OF POTENTIAL EVAPORATION AND TIME} AND INITIAL NATER CONTENTS FOR EACH HUMUS-SOIL CORE. CORE: A-2 CUM CU“ FRAC TIME EVAP EVAP DAYS HOURS CM 0.0 0 090. .000 1.3 32 0.4 .042 3.3 30 0.8 .030 6.4 154 1.2 .122 993 224 1.6, .153 12.3 296 2.0 .192 15.3 363 2.3 .223 18.3 440 2.6 7.251 21.4 513 2.8, .276 24.3 584 3.1: .301 29.3 704 3.5 _.340 33.3 300 3.8 .368 37.3 896 4.0 .393 4195 992 4.3 3417 5093 1208 4.9, .473 INITIAL HATER CONTENT (CM) 13.3 POTENTIAL EVAPORATION A9 INITIAL HATER CORE: CUM TIME EVAP DAY§ HOURS CM 0.0 O 0.0 1.8 42 9.4 3.6 87 0.7, 6.6 159 1.2 9.6 231 1,4, 12.6 303 1.6 16.6 399 1.9_ 19.6 470 2.1 _23.6 566 2.3 26.6 638 2.5 32.6 783 2.9. 37.6 903 3.1 41.6 999 3.3 49.7 1193 3.5, 52.6 1263 3.6g 0‘. 2 can FRAc EVA? .000 .041 ..0’4 .116 '9140 .165 .192 .210 .253 .250 _.292 .611 .326 .352 .363 CONTENT (CV) 10.0 A43 CUM EVAP CH AbAUUUUUNNNI-‘POO 0.00.00.00.0000 OUPOVANOVUTNOUVO CUM EVAP CM «bJQ-fiU‘NUCflNNNPO-‘OO ooooooooooooooo CUM FHAC EVAP .000 .077 .146 .201 .240 .272 .299 .324 .347 .368 .402 .427 .450 .472 .524 9.1 3 CU" FRAC EVAP .000 .058 .115 .192 _.243 .282 .314 .355 .371 .411 .427 .433 .457 _,466 9.3 0.76 CH/DAY A44 CUM EVAP cw m&$h®(d“(flNNNI-‘POO oooooooooooooo. ~mcnahcucamfsmvoommo-buuo CUM FRAC EVAP 0000 .051 .112 .176 .221 .258 .289 .318 .343 .367 9405 .434 .459 .485 _4549 1090 0.43 CH/DAY A9 A24 CUM EVAP CM #beO-IOJGNNNHPOOO W5NO£DONOVCN~O$CDJIO O O O O O '0 O C O O C O '. O O CUM FRAC EVAP .000 .042 .083 .142 1192 .235 ,276 .295 .327 .345 .388 .410 .424 .449 .459 9.4 A- CUM EVAP O 3 mac-Auuuummmmpoo ecu-00.000.40.04- rooygaog>04>nio~uou304043 5 CUM FRAC EVAP .000 .075 .161 .237 .284 .322 .356 .386 .412 .437 .480 .509 .537 .565 .628 8.2 A-5 CUM EVAP O 3 AHDJLGCHONuCanohawtacao 0.0.0.0....0000 UNOOV‘NOO$O#GAO CUM FRAC EVAP .000 .052 -3103 .174 .243 .300 .345 .371 .400 .419 .464 .483 .497 .521 .533 8.0 A*AVG CUM EVAP CM W‘b‘UuuUNflJNpt-‘OO cocoooo-oooooo-o WH\flOdOFD&J0fi3)Lbf‘VF‘O\D CUM FRAC thP .000 .060 .122 .181 .222 .257 .288 .316 .341 .364 .403 .431 .456 .431 '9540 9.4 A-AVG CUM EVAP ##04010404 (ANNNHHOOO O I NHOQONDDOM‘OAO#O CUM FRAC EVAP .000 .047 9093 .154 .203 .242 .278 .298 .324 .342 .384 .403 .417 .440 .451 Elm." APPENDIX POTENTIAL EVAPORATION = 118 (CONTIVUED). CORE: 8-2 CJM CUM FRAC TIME EVAP EVA? DAYS HOURS CM; 0.0 o 0.0; .000 1.5 32 0.2- .058 6.4 154 o.9l_.156 9.3 224 1.24 .182 12.3 296 1.5. ”239 15.3 368 1.9 .289 13.3 440 2.1:_.362 21.4 513 2,4, .373 _ 24.3 584 2.6,-.412 29.6 704 3.0% .413 33.3 sou 3.5, .515 37.3 896 3.6 .554 41.3 992 3.8 .594 50.3 1203 4.4 .690 INITIAL HATER CONTENT (CM) 6.4 POTENTIAL EVAPORATION CORE: 892 CJM CUM FRAC TIME EVAP EVA? DAYS HOURS CM‘ 000 0 000 .000 .108 42 0.2.-.028 3.6 87 003‘ .055 6.6 159 0.53 .087 9.6 231 0.7 .122 12.5 303 0.9- .155 16.6 399 1.2‘ .197 19.6 470 1.3.-.225 23.6 566 1.6 ‘.265 29.6 638 1.8,-.297 32.6 783 2.2 .3/9 3799 903 2.5: .416 41.6 999 2.6 .443 49.7 1193 2.9 “.485 52.6 1263 3.0 .502 INITIAL HATER CONTENT (CM) 5.9 8'3 CUM CUM FRAC EVAP EVAP CM .000 .073 .155 .252 .329 .393 .445 11.490 .527 .557 .606 L-3637 .663 I -1689 .743 _r ouunamuuronsmo4+spwdcache hyo\qogaouvc{gcr.no¢>o.c O 0.. O. 0“... O. O 4.1 8-3 CUM CUM FRAC EVAP EVAP CM g'.000 ._.052 .102 ._.161 .213 .259 .315 .353 .404 .439 .523 .553 .570 .598 3611 afiflbldhflO‘dmfiflfiHO\J&hJC> NJNHUBDNH‘I‘F‘HJJCDCMDCDc3 4.2 0.76 CM/DAY 8-4 CUM CUM FRAC EVAP EVAP cm .000 .048 .106 9133 .252 _.314 .371 .418 .459 h .497 ‘ .555 ..4597 .630 _o664 .726 .OOOOOOOOOQOOO (uc1m~quuvr&cww4bpfn\nm«D UCHNHVRJNHUF'Pt‘Hwacnacb 4.5 0.43 CM/DAY 824 CUM CUM FRAC EVAP EVAP CM .000 .036 .067 .9109 .151 .192 .240 .275 .324 4359 .441 .482 .508 9549 .568 O kuLsc~Hwaq~anono~4uuunJc. Nlunsmwvhtflwirhocncroc:c3 O O O O O O O O O C O O O O 4.4 8-5 CUM EVAP .Q 3 O . v UGUUNNNNPHPPOOO V¢uuooappouoouo QODOO‘OOOOOQQQO CUM FRAC EVAP .000 I - .055 .121 .213- .287 -5353 .411 .4. 465 .512 .556 .628 . .663 .704 .735 .789 4.7 BPS CUM EVAP O 3 O O. '0 O. ‘0. . O O D O . BDNHDBJAH4F4PJ‘P‘OCDCHD(D @‘QOMthm¢>JJUC)m\EOHUCD CUM FRAC EVAP .000 $039 .073 3128 .178 @229 .289 3331 .388 .429 .530 .575 .605 .649 .671 B-AVG O C I EVAP o O 3 Mnfififlr-.. .7 “(NOHNFORJNEOHWAP‘O040\fiOJO ”fl CUM FRAC EVAP .000 .052 3111 .190 .254 -5315 .369 .3416 .458 3496 3556 n594 «630 ._.665 _.733 B-AVG CUM EVAP C I 3." . u “.7 NJNWONJNF‘F‘HWJF9043CDOWD coo-0.0.0.0.... \.o.noammno»aruc>m<>oam CUM FRAC EVAP .000 .037 .074 .118 .162 .204 .255 .290 .338 3373 .460 £498 .524 .562 .580 APPENDIX POTENTIAL EVAPORATION CORE: TIME DAYS HOURS 0.0 o 1.3 32 3.3 80 6.4 154 9.3 224 12.3 293 15.3 368 18.3 440 21.4 513 24.3 584 29.3 704 33.3 800 37.3 896 41.3 992 50.3 1208 INITIAL HATER CONTENT (CM) POTENTIAL EVAPORATION CORE: TIME DAYS HOURS 0.0 0 1.8 42 3.6 87 9.6 231 12.6 303 16.6 399 19,6 470 23.6 566 26.6 638 32.6 783 37.6 903 41,6 999 49.7 1193 52.6 1263 INITIAL HATER CONTENT (Cm) uuummNmHHr-Hoooo V‘ur‘m‘omo'mopdombmo oo_ooooooopooooo T cocoooooooo-oooo bar‘ombapom-JmaMo N10 MNHPHHO-‘oooooo C-2 CJM FRAC EVAP .000 .044 .093 .160 .215 42/2 .324 -.374 .421 ,437 .541 .589 .656 .619 f".763 4.8 C-2 CUM FRAC EVA? ‘.000 .068 '9071 .110 .147 .133 .227 .257 .301 .336 .423 .467 .499 .546 3567 4.2 (CONTIVUED). = 0.76 CM/DAY 119 C53 CUM EVAP CM + N'DOJO‘AH'OVUTNOOUIUO 7*" ‘ " r" ‘ r‘ " C...- O 00...... O urcunvnaNHAh9Hwahso<2c50 I CUH FRAC EVAP .000 .064 .117 ,133 .241 ,302 .358 3411 .459 .507 .581 ”631 .674 _J708 .773 4.1 0.43 CM/DAY C93 CUM EVAP CM AHVFOKJPtJh4Hddc>ooc3c>o C-5 CUM FRAC EVAP .000 .053 .109 .176 .231 .285 .339 .392 .439 .490 .567 .619 .665 .706 .782 C-5 CUM FRAC EVAP .000 .035 .070 .107 .141 .176 .214 3241 .286 .318 .411 .461 .495 .552 C-AVG O C 3 EVAP C I ‘0..- ”‘1‘.- (dadmron3M9AF3H94hiocac:a O O O '0 O O O O O O C O O O O me44164nhto~qunuca\pbnao CUM IRAC EVA? .000 .044 .088 - 3144 "242 328/ .332 "373 O 415 .481 3527 .569 ,608 .686 C-AVG CUM EVAP C X _. —. -—-_. 00.00.00.000... buHombNO-‘OCDOWHNO NMNNHHHPCOOODOD CUM FRAC EVAP .000 .033 .062 ,,095 .125 .154 .190 .215 .251 .230 .359 .399 .426 .472 L3493 APPENDIX POTENTIAL EVAPORATION = POTENTIAL EVAPORATION I. (CONTINUED). CORE: 0- CUM TIME EVAP DAY: HOURS CM 0.0 o 0.0 1.8 42 0.2 3.6 87 0.3 .16.6 159 0.5 9.6 231 0.6 2.6 303 0.0 16.6 399 1.0 19.6 470 1.1. 23.6 566 1.2 26.6 638 1.4; 32.6 783 1.6 37.6 903 1.7. 41.6 999 1.0 _49.7 1193 1.9 52.6 1263 1.9 INITIAL HATER CONTENT (CM) CORE: 092 CUM CUM FRAC TIME EVAP EVAP DAYS HOURS CM 0.0 0 0.0 .000 1.3 32 0.21 .0/7 393 80 004‘ 9154 6.4 154 0.8._.266 9.3 224 1.1...362 12.3 296 1.3. .462 15.3 368 196'los42 18.5 440 1.0, .619 21.4 513 2.0 .676 _ 24.3 584 2.1.-.734 29.3 704 2.3 .806 33.3 800 2.51-.845 37.3 896 2.5 .817 41.3 992 2.6: .899 50.3 1208 2.7 .938 INITIAL HATER CONTENT (CM) 2.9 2. CUM FRAC EVAP .000 .0/0 .125 4190 .249 .310 .381 .429 .491 .645 .678 .705 :.740 .762 7.5 CUM EVAP CM 0.00.0.00000... NNNNNFPPHPPDOOO 120 3 CU” FRAC EVAP .000 ‘087 .183 0.296 .382 ,.454 .512 4.564 .604 .641 .694 .734 0.76 CM/DAY D? 024 006 EvAP CM NMNNNNPFFPHOOOO 3 0.43 cH/DAY D CUM EVAP n 3 nomnunaprswuar6pwacaoc3c3 turbosa<1oxnouucamxrauuc: ~3 cum raac EVAP- .000 ..068 .129 ..206 .279 .345 .414 .457 .512 .554 .651 .680 .700 1.731 .749 .9 CUM FRAC EVAP 094 CUM EVAP c4 1» AJPJ‘F‘HI‘P‘PW‘CLDCDCHD(D cuocpxuassmrfcaquuuun:o_ O O O O O O O O O D O O O O O CUM FRAC EVAP .000 ".063 .114 ..176 .234 .287 .347 _.388 .444 .484 .584 -9622 .643 .678 .698 2.8 0’5 CUM CUM FRAC EVAP EVAP CM .000 1.063 '0127 1.210 -.281 -..346 ;.411 _.464 .511 1.554 .617 4661 .699 .736 0807 O O 0 D O C O O O O O 0 O C O f0319H05:aru1345ywp~aatuc> NIONHthPWAF‘Pchaocacao 3-3 0-5 CUM CUM FRAC EVAP EVAP CM 13.000 .047 .092 .196 .243 ...145' D‘AVG CUM EVAP CM 1" \IU‘I#01NOGI\JUIOJOOUTN_O’4 —— 0. 1 NNMNNNHPHPHOOOO . Q C O O O '0 O O O .0 O O O CUM FRAC EVAP '.000 .076 .154 .254 .337 3417 0487 _.551 .603 “1.653 .720 .762 .795 .823 .878 3.0 D-AVG CUM EVAP CM 1 r. _ I." 7 00000000000000 0 ODOQV‘HHCQVWCAND NNHHHHHPH-OOODDD CUM FRAC EVAP '.000 ._»061 .114 3173 .238 .294 .352 1400 .457 .497 .598 3634 .658 __.695 .715 2.9 APPENDIX 1. POTENTIAL EVAPonATlaN = 121 (CONTIVUED). 0076 CM/DAY CORE: 0.2 693 E94 E-5 E-AVG CJM CUM cum 000 000 004 FRAC cum r040 cum FRAC cum FRAC cum FRAC TIME EVAP EVA: EVAP EVAP EVAP EVAP EVAP EVAP EVAP EVAP 0476 HOURS CM 00 04 CM cm 0.0 o 0.0 .000 0.0 .000 0.0_ .000 0.0 .000 0.0. .000 1.3 32 0.3 ..064 0.2 .030 0.3. .050 0.2 .036 0.3. .037 3.6 80 0.7 .081 0.5 .064 0.7 .117 0.5. .000 0.6 .004 6.4 154 1.2 -.150 0.8 _.115 1.3. .196 0.9 .135 1.1. .148 9.3 224 1.7 .214 1.2. .161 1.6. .249 1.2' .105 1.4 .202 .12.3 296 2.2.;.274 1.5 _.209 1.9. .295 1.6 .234 1.0, .253 15.3 360 2.6} .324 1.9' .256 2.1 .335 1.9~ .201 2.11 .299 18.3 440 3.0 .364 2.2 1.302 2.4 .360 2.2. .324 2.4. 6340 21.4 513 3.2 .397 2.5. .340 2.5 .390 2.4 .363 2.7 .377 24.3 504 3.5 .1420 2.0 .392 2.7 .427 2.7: .400 2.9 $412 29.6 704 3.0 .4/2 3.3 .461 6.0 .473 3.0 .454 3.3 .465 33.3 800 4.1- 1501 3.7 1.500 3.2. .506 3.3, .492 3.6...502 37.3 096 4.3 .527 4.0 .546 3.4- .532 3.5 .524 3.0; .532 41.3 992 4.5 .553 4.2 4.500 3.61 .550 3.7, .553 4.02 .561 50.3 1200 4.9 .606 4.7 .651 3.9 .614 4.1, .610 4.4: .620 INITIAL HATER . CONTENT (CM) 4.2 7.3 6.4 6.6 7.1 POTENTIAL EVAPORATION = 0.43 CM/DAY CORE: E-2 5.3 E24 E-5 E-Ave CUM cum cun cum CUM CUM FRAC CUM FRAC 004 FRAC CUM FRAC cum FRAC TIME EVAP EVAP EVAP EVAP EVAP EVAP EVAP EVAP EVAP EVAP DAYS HOURS cm 00 04 ‘ cu cm 0.0 0 0.0 .000 0.0".0oo 0.0 .000 0.0 .000 0.0 “.000 1.8 42 0.2 .024 0.2 _.024 0.2 _.030 0.2 .026 0.2 1.027 3.6 07 0.4 .049 0.3 .040 0.5 .075 0.3 '053 0.4 .055 1-6.6 159 0.7.-.085 0.6; .077 0.3 _.128 0.6 4.086 0.6--.093 9.6 231 1.0. .121 0.8 .106 1.1 .100 0.0 .119 0.9, .129 12.6 303 1.2 1.150 1.0 .133 1.4 -4229 1.0 .152 1.2. .165 16.6 399 1.6 .204 1.2 .169 1.8 .207 1.3 .192 1.5' .210 19.6 470 1.9 v.230 1.4 .196 2.0 _.321 1.5_ .222 1.7. .242 23.6 566 2.2 .265 1.7 .234 2.2 .350 1.7 .263 2.0; .203 26.6 630 2.5 .319 2.0. .267 2.4 ".382 1.9_1.293 2.2, .313 32.6 703 3.1 .391 2.7 .365 2.7 .441 2.5 .374 2.7. .391 37.6 903 3.3 .419 3.1; .417 2.9 .466 2.7: .414 3.0; .428 41.6 999 3.5 .460 3.3 .449 3.0 .402 2.9 .430 3.1. .451 49.7 1193 3.7: .466 3.7,_.501 3.1 _.509 3.2 -.401 3.4 .400 52.6 1263 3.0 .479 3.0 .521 3.2 .520 3.3 .490 3.5. .503 INITIAL HATER * - CONTENT (CM) 7.9 7.3 6.2 6.5 7.0 122 APPENDIX 1. (CONYIVUED). POTENYIAL EVAPORATION = 0476 CM/DAY 000E: 0.2 $43 064 r-5 F-AVG 00M 00M 000 CUH‘ 00M CUM FRAC 00M r040 004 r040 00M r240 00M F010 TIME EVAP EVA? EVAP EVAP EVAP EVAP EVAP EVAP EVAP EVAP DAYS nouns cM 0M 0M 0M 00 0.0 0 0.0 .000 0.0 .000 0.0 .000 0.0 .000 0.0. .000 1.3 32 0.3 .034 0.2 .033 0.2. .030 0.3.-.037 0.2 -1034 303 8° 044 4061 0.4' .066 064‘ 4064 065 4075 095- 39067 6.4 .154 0.7- .096 0.7 .109 0.7. .100 0.9- .124 0.8 5109 9.3 224 0.9, .127 1.0 .149 1.0 .146 1.2 .168 1.0 .147 2.3 296 1.2.-.159 1.2 .189 1.2 ,.105 1.5...210 1.3“ .106 15.3 360 1.4 .180 1.5 .226 1.5 .222 1.0. .252 1.5 .222 18.3 440 1.6 .217 1.7 .257 1.7 ;.257 2.1 1.293 1.8 .256 21.4 513 1.0 .244 1.9 .287 1.9 .287 2.4: .329 2.0% .207 24.3 584 2.0 1.271 2.0. .315 2.1; .321 2.7 _.365 2.2. .310 29.3 704 2.3 .315 2.3 .360 2.5 .374 3.1 .421 2.6; 1360 33.3 000 2.5 .346 2.5. 1391. 2.7. .411 3.4.1.461 2.0. .403 3703 896 248 43/6 2.7 .421 3.0 94‘6 347:‘4500 340; 0436 ‘113 992 3.0 .405 2.9.-.449 3.2 0478 3.91-0535 302. .0467 50. 3 1200 3.5. .476 3.4 .523 3.6 .546 4.6; .623 3.8. .543 1NIT111 HATER ' " “ CONTENT 400) 7.3 6.5 6.7 7.3 6.9 POTENTIAL EVAPORATION = 0.43 CH/DAY CORE: F92 703 F34 FP5 F~AVG 00M 00M CUM 00M CUM 00M r040 00M r040 000 FRAC 00M 0040 00M F040 TIME EVAP EVAP‘ EVAP EVAP EVAP EVAP EVAP EVAP EVAP EVAP DAYS 00005 CM 0M CM CM CM 0.0 0 0.0 .000 0.0".000 0.0. .000 0.0 .000 0.0” .000 1.8 42 0.2 .027‘ 0.2. .020 0.2 _.023 0.2; 1027 0.2 .026 3.6 87 0.3 .046 0.3. .052 0.3 .045 0.3» .051 0.3? .048 6.6 -159 0.5 .065 0.5 3.081 0.5.1.070 0.5-..070 0.5;".073 9.6 »231 0.6 .084 0.7 .109 0.6~ .094 0.7 .103 0.7‘ .097 12.6 303 0.7 .102 0.9 1.136 0.8._.116 0.9L-.128 0.8; .120 16.6 399 0.9 .126 1.1 .169 1.0‘ .141 1.1 .161 1.0 0149 19.6 470 1.0 -.143 1.2 .193 1.1 -.162 1.3-1.104 1.1L .170 23.6 566 1.2 .166 1.4t .224 1.3 .191 1.5 .216 1.3 .199 26.6 638 1.3 .186 1.6 _.240 1.4- .213 1.6. .239 1.51:.221 32.6 703 1.7 .240 2.0; .309 1.9 .283 2.1 .304 1.9 .283 37.6 903 1.9 .266 2.2 -.336 2.1- .315 2.3 .339 2.11 .313 41. 6 999 2.0 .285 2.3. .355 2.3' .335 2.5. .364 2.3. .334 49. 7 1193 2.2 .310 2.51 .384 2.5- .371 2.8 .407 2.5. .369 52 6 1263 2.3, .332 2.5:..397 2.6 .386 2.9 .425 2.6 .305 INITIAL HATER ‘5 ’ - CONTENT (CM) 7.0 6.4 6.0 6.9 6.0 APPENDIX 14 (CONTINUED’4 123 POTENTIAL EVAPORATION = 0476 CH/DAY G-S POTENYIAL EVAPORATION CORE: 602 CUM CUM FRAC TIME EVA? EVA? DAYS nouns CM 040 0 040 4000 143 32 042 14029 343 80 0.41‘4064 54C 154 047.14109 1243 296 143._4197 1543 360 146' .260 1543 440 148-142’4 2144 513- 240 .4309 -2045 534 243.-4344 2943 704, 247' 4‘03 3343 000. 249 -4045* 37.3 096 3.2 .483 4143 992. 345114524 5043 1208 441‘ 4611 INITIAL HATER CONTENT (ON) 646 COREO 3.2 CO" CUM FRAC< TIME EVAP EVAPs OAY§ HOURS CH 040 0 0405 4000 ,145 42 0.2; .030 346 I7 04‘ 4059 _645 -159 046, 3097 946 231 048 .134 1246 303 140 4169 16.6 399 1,3 .212 -1945 470 145. 1241 2346 566 147 4281 2645 630 149! 4311 32.6 783 244' 4391 3746 903 247-_.439 4145 999 249 4‘69 i 49.7 1193 3.2 .523 5246 1263 3.3. 4551 INITIAL NATER CONTENY (CM) 641 cumnunamuarstArtocacro4: .COOOOOO‘OOOOCO CUM EVAP CM WPO£P@°*NP@WQN° CUH FRAC EVAP 1000 .028 .053 .036- .122 _.157 .188 “.220 .252 .236 .342 1.386 .425 .466 .567 6.2 084 CUM EVAP CM ‘WGGGMNNPPFOOOO 0.0-0.0.0.0.... NNWNOOGI‘OUNOWNO 1...r_1 3 0.43 OH/D‘Y 003 CUM EVAP CM hoununawwér-vwac:owacaono 99~92w~9o~wymeo- C.............. CO" FRAC- EVAP .000 .020 *.038 ..059 .032 ”104- 3134 .153 .133 4208 .276 .315 .342 “.393 .413 6.4 CUM FRAC EVAP .000 4037 4079 4132 4132 4230 4276 .318 1359 4396 4456 . J497 4535 4563 4643 45 0.4 CUM EVAP cM _ -_ - f -. i 7". uuummm'flt‘flflococo “OPOOO‘OO.“OV‘NO O Q . O O O O Q C O O O O O O CUM FRAO EVAP 4000 4029 4059 4097 4130* -4169 4210 ; 4240 4200 -4810 4421 0427 0‘63 #4506 0524 648 805 CUM CUM FRAC EVAP EVAP CH 040 4000 0.2 .034 045. 0072 048 _4121 140‘ 4164 143' 4207 146' 4252 149. 4296 241! 4337 244 4377 248. 4444* 341._4500 344} 4547 347; 4590 4.2 4676 643 9.5 CUM CUM FRAC EVA? EVAP CH 040f 4000 041. 4022 042 0042: 0.4; 4063‘ 046 5095 047. 1122' 049 4154‘ 1.0 -4178 142 4214 144. 4240 149 4319 241- 4360 243 4339 246 4433 247' 4459 548 GwAVG CUM FRAC EVAP mo O '”’ ‘3 H , O D O O O O O O O O O O. C O ciouthNMUHJPWAhfiHwacaamo 4*C3O‘HUH4CD\JOFUCDVJbNJo CUM FRAC EVA? 4 O 4000 3036 4075 4127 4177 4225 4281 4316 4359 4386 .456 3486 4507 4538 4552 5.5 125 APPENDIX (CONTINUED). POTENTIAL EVAPOPATIOV : 0.76 CH/DAY LURE: K-2 Mo} n-4 K-5 K-AVG GEN 993 CUM __ ____CUN_ QUM_H.._ CUM FRAC CUM FRAC CUM fHAC CtM FRAC cuM FRAC TIME FMAE_E1LE__EVAE_EyAPW_EVAH“:VAP_WEVARuhVéP_ __EVAP_ Ev_AP _“_ bAYb HOURS CM Cm Cm CM CM 0.0 u 0.07.003 0.0 .090 “0797.uou_ 07079300 0.0 .vou l.é_ 92 _Q.§. .35; _Q.3, .099 _944. 404L_.0.5E .059E_0.3- 4&45 _ 3.3 do o,/ .121 0,5 .1U6 0.9 .092 0.7 .107 0.6 .106 6 14 1 5 4 1 Lg, .1 Egg—.401 9..- .1 1 I 7.. _EJ 1_?_ .1164____1l.é_ 1-1 96...; L1,- 1.19 2.___. 9.6 224 1.9 .326 1,4 .270 1.4 .239 1.5 .272 1.6 .277 1? 3 29° 2.5 -412 1.§; -é£9__3¢l_ 3§QZ__2.§M .999 243. 41?? 15,3 36b 2./ .464 2.1. .492 2.0 .500 2.5 .555 2.3, .906 15:3 990 71?. .599 2.3} v9?Q 219. 4914 _2L93 1929M.2.§, 4995w__" 21.4 513 3.1 .533 2.5‘ .405 2.9 .449 3.01 .497 2,5. ,450 29.5 5&9 E4é- .562 2.2- .?f 6.2.7“ 50.6 12Gb 4.8 .721 3.6‘ .096 5.9 .b4u 4.2' .646 3.9 67; INITIAL WATER ‘ ' - _ CuhTEVT (CM) 5.8 2.2 9.: 6.5 5.5 POTENTIAL EVAPORATION : U. 45 CM/UA:. UJRE: «-2 R-3 n- 4 K-S K-AVG CUM CUM _CJM CUM____“__~§UN_ _ __ CUM EéAC CUM +HAC CUM 7f7RAC CCM FRAC CUM FHAC TIME EVAP EVAP EVAP EVAP tJAP EVAP EVAP EVAP FVAP EMAD DAYS HUUKS CM CM CM CM ch 0.0 u 0.9“ 7679—9573"_.TUUU”‘9.U" .000 076- .000 0.6” IBOU"_”’ 1.8 42 0.2 034 0,2 .034 u.a .030 0.2 .029 9.2“ .n31___fl 6.0 b7 0.97 .0787"h.4 .009 0:37 .Uo?‘”fi.4“ .ool"wn.4 .to7 6,6 159 n.7# .152 0.0. .113 0.0 .106 0.7‘_.106 0.6 .114 9.0 231 1.9“ .192 0.8“ 7136 079” .149 1Tfiw‘Ti95 079" 7582 12,6 343 1.6 .246 1.0 .195 1.1 .192 1.2 .197 1.2 .205 10.6 399 177777334_“i.37 .252771247 .249“”1.67 .253 {:59 .237 19.0 47v 2.0 .364 1.5‘ .293 1.02 .290 1.9 .294 1.7 .310 23,5 560 273‘ T423971787".349 1:9“ ,34g““2;§“'754§ ”2ff”'}3o4‘“’” 26 9 6 67557 2L5 ' 47757777 23.1 ' 5-9 l 2 '-.1 7 ' 757137} 7.2.1 4 .. 9.19 2.1.3... 4.9.01 52,0 783 2,5 .35? 5,5 TESi‘—ZTS" j453“é,3" .446 2,7 .476 57.6 909 _9L9__1§91_3217- :91? -391, ;9§%_.390 JEZZWNZJB; :505___~ 41.6 999 3.0 .564 2.9+ .941 2.6 .juo 3.1 .494 2,9, .923 49 7 11?.J .33.?” $914.4 magi géaLsgéf .SZIJA- .591 __ 52. b 1265 3.2. .602 3.1. .965 6.u_ .951 3.4 .533 3.2. .564 INITIAL wATER ’ — CONTENT (GM) 5.4 5.3 5.5 6.3 5.6 _-Cv APPtNDIx I. POTENTIAL,EVAPORAT10N CORE: M-2 CUM CUM FRAC TIME EVAP EVAP DAYS HOURS CM 0.0 O 0.0 9000 1.3 32 0.7 .094 3.3 80 1.3 .1/8 6.4 154 1.9 .251 9.3 224 2.2 .298 12.3 296 2.5.-.341 15.3 368 2.8 .376 18,3 440 3.1, .414 21.4 513 3.3 .436 24.3 584 3.4- .462 29.3 704 3.7' .502 3393 800 399’ .527 37.3 895 4.1: .552 41.3 992 4.3 _.5/6 50.3 1208 4.7 .628 (CONTIVUED). INITIAL HATER CONTENY (CM) POTENTIAL EVAPORATION CORE: H-Z CUM CUM FRAC TIME EVAP EVAP DAYS HOURS CM 0.0 0 000 0000 1.8 42 0.5, .064 3.6 57 1.0 .132 6.6 159 1.7_-4223 9.6 231 2.2 .292 2.6 303 2.5 “.351 16.6 399 2.8 .368 19.6 470 3.0__.390 23.6 566 3.2‘ .415 26.6 638 3.3,_,433 32.6 733 3.6 .476 3706 903 3.3, .994 41.6 999 3.9 .508 49.7 1193 490 “.529 52.6 1263 4.1 .540 INITIAL HATER CONTENT (CM) 7.6 7.5 126 = 0.76 CM/DAY M- CUM EVAP CM '. $bb¢UCflWUNNNPHOO ooooooooooooooo OAUPOObNOO‘NVDbO 3 CUM FRAC FVAP ° .059 .130 .295 .351 $390 5422 .452 ”477 .517 4545 .569 .590 .639 7.5 H93 CUM CUM FRAC EVAP EVAP CM 0.0‘ .000 0.41 .050 0.8 .097 1.2__.159 1.7 9223 2,2, .235 2.7 .354 3.02-9392 3.3 .432 3.5, .457 3.9 .511 4.11 .529 4.2 .543 4.3. .563 4.._ :573 7.7 CUM EVAP cm O&GGUUGNNNNFPOO 0,43 CM/DAY H94 CUM FPAC EVAP .000 .077 .167 .237 .281 3316 .347 .374 .396 .418 .454 9481 .506 .530 9557 7.6 M54 cum ev.p CH UUUUUWNNNNPFOOO 00.00.000.000... ODOWbO-‘VONU‘NOWG’bO CUM FRAC EVAP ".000 '_.054 3109 .137 .249 .289 .328 .350 .375 _.393 .435 .455 .469 .494 .504 7.8 M95 CUM EVAP O 3 r - bAUGGUNNMNNI-‘PDO CUM FRAC EVAP .000 .093 .169 .232 .276 4316 .349 .379 .406 ”.431 .473 .501 .528 4554 .614 H95 CUM EVA? 0 3 uuuuummmmwwpooo mmumosw.mooum;o 0.. .‘C..."... «O CUM FRAC EVAP .000 .054 .109 .150 .231 .272 .310 .334 .355 .381 .429 .450 .465 .488 .500 7.1 M-AVG O C 3 EVAP O I ‘#‘UUWUNNNNHHOO 00.00.03.000... ONOQOGHOVWHONOD CUM FRAC EVAP V'.ooo . .061 .161 .236 .288 .331 .366 .397 .423 - 5447 .487 .514 9539 _ $563 @617 M-AVG ('3 C 3 EVAP C) 3 buuuCACflUNNNPI-‘DOO coo...ooootoooo OOVOWHOGO‘N0hmfiO CUM FRAC EVAP .000 .055 .112 "-3187 .249 .295 .340 .367 .395 .417 .463 .483 .497 .519 .530 1““: APPENDIX 11. POI. EVA? CH/DAY 0.76 0.43 DEN§ITY 0.7. 0.43 DENSITY 0.7. 0.43 DENSITY 0.76 0.93 DENSIYY 127 FoR EACH HUMuseSOIL CORE. SIYEQ~ CORE TIME DAYS A92 0 4'2 0 53 tG/cn3) A23 0 16 30 51 A93 0 17 33 53 (G/cn3) A95 0 53 (G/cn3) 1.9 .579 .240 0228 .157 .444 .173 .105 .104 .253 .325 .073 .041 .017 .291 .065 .007 .007 0661 .617 .341 9234‘ .262 .541 .293 .231 .106 .288 .338 .075 .052 .043 .379 .154 .098 .055 .577 3.8 .354 .300 .212 .071 .327 .243 .215 .149 .454 .304 .189 .090 .033 .276 .133 .104 .077 .616 .368 .295 .198 .072 .342 .309 .244 .056 .496 .288 .107 .089 .068 .350 .234 .111 .069 .612 6.4 .366 .330 .320 .249 .402 x.s.1 .317 . 93 .455 .287 .220 .167 .121 .367 .254 .270 .225 .629 .352 .336 .282 .215 .344 .286 .275 .224 .429 .289 .235 .177 .146 .361 .257 .226 .152 .565 DEPTH 8.9 .351 .332 .325 .276 .376 .344 .300 .301 .517 .272 .211 .180 .165 .313 .194 .230 .193 .659 .395 .349 .317 .205 .394 .340 .336 .283 .465 .292 .232 .137 .158 .353 .218 .138 .161 .572 (CH) 11.4 .357 .347 .318 .288 .372 .336 .338 .304 .510 .299 .239 .204 .203 .371 .283 .262 .A261 .621 14.0 .361 .331 .34. .278 .374 .322 .326 .300 .509 .325 .246 .222 .199 .356 .247 .226 .222 .596 .402 '>.293 .260 1.230 .419 .311 .252 .234 .575 .260 .200 .164 .143 .296 .202 .176 .162 .691 16.5 .345 .284 .259 .210 .340 .303 ..254 .229 .565 .325 .224 .198 .179 .357 .250 .209 .203 .620 .336 .235 .196 .180 .331 .196 .170 .134 .622 .269 .179 .147 .115 .286 .132 .113 .125 .650 VOLUMETRIC HATER CONTENT AS A FUNCYION OF DEPTH. TIME. AND POTENTIAL EVAPORATION} AND BULK DENSITY 19.0 .363 .301 .241 .203 .340 .286 .244 .211 .595 .309 .239 .195 .186 .360 .265 .191 .200 .620 .337 .212 .201 .171 .321 .172 .164 .135 .646 .316 .190 .170 .141 .296 .123 .109 .081 .666 ;,y APPENDIX 11. P07. SITE! 5V4? CORE 710E CH/DAY DAYS 0.76 892 0 16 30 51 0.43 8’2 0 17 33 53 DENSITY (G/cn3) 0.76 8'3 0 16 30 51 0.43 8‘3 0 17 33 53 DENSITY (610.3: 0.76 894 0 16 30 51 0.43 8’4 0 17. 33 53 DENSIYY (07083) 0.76 895 0 16 so 51 0.43 8'5 0 17 as 5. DENSITY (c/cn3. 1.9 .265 .099 .055 .034 .126 .050 .026 .016 .002 .358 .190 .197 .152 .254 .135 .137 .006 .254 .332 .160 .135 .075 .235 .132 .085 .001 .094 .412 .180 .106 .123 .356 .271 .073 .061 .257 (COVIINUED). 3.8 .449 .381 .149 .066 .354 .333 .130 .070 .134 .294 .252 .124 .140 .188 .192 .202 .012 .599 .440 .320 .148 .097 .408 .331 .131 .015 .264 .346 .286 .160 .093 .322 .237 .170 .006 .610 128 6.4 .536 .469 .386 .202 .576 .499 .404 .287 .232 .155 .131 .069 .066 .167 .085 .095 .044 .793 .271 .213 .138 .058 5360 .298 .256 .196 .540 .143 .120 .090 .017 .183 .117 .083 .055 .859 DEPTH (CH) 899 11.9 .527 .222 .440 .171 0‘09 .163 .305 .135 .587 .210 .524 .193 .440 .150 .397 .124 .227 .650 .147 .100 .119 .065 4085 .036 .050 .024 .192 .115 .092 .056 .103 .047 .079 .045 .000 .818 .211 .106 .153 .066 .189 .062 .119 .047 .196 .143 .163 .101 .229 .084 .096 .070 .693 .827 .140 .130 .094 .080 .072 .043 .034 .036 .186 .160 .125 .101 .093 .064 .077 .072 .862 .836 14.0 .116 .054 .059 .034 .109 .091 .057 .064 .823 .108 .093 .055 .045 .130 .074 .057 .055 .775 .129 .091 .075 .068 .093 .074 .051 .063 .781 .138 .095 .061 .062 .133 .078 .065 .049 .732 16.5 .131 .086 .084 .055 .093 .090 .055 .050 .797 .100 .065 .044 .034 .106 .069 .034 .053 .771 .096 .066 .051 .038 .065 .063 .025 .053 .752 .167 .092 .077 .054 .150 .089 .061 .075 .784 19.0 .126 .101 .079 .052 .084 .056 .039 .028 .813 .109 .073 .076 .074 .120 .045 .042 .056 .743 .150 .137 .164 .106 .203 .203 .139 .178 .685 .152 .088 .066 .049 .138 .079 .053 .076 .804 APPENDIX 11. (CONTINJED). POI. EVAP -CH/DAY 51TE9 CURE TIME DAYS 0.76 C92 0 0.43 C92 0 53 (G/cn3) _ 023 o DENSITY 0.76 093 0 53 DENSITY (G/CM3) 0.76 C" 0 16 30 51 as. o 53 DENSITY (excn3) 0.76 ”-0'5 0 53 DENSITY (srcn3) 1.9 .200 .013 .000 .011 .088 .002 .016 .020 .043 .213 .035 .027 .045 .163 0006 .003 .013 {050 .375 .149 .101 .143 .243 .102 .091 .025 .036 0190 .021 .015 .021 .107 .008 .004 .011 .007 3.8 .441 .198 .032 .007 .279 .133 .002 .011 .135 .246 .217 .075 .033 .246 .100 .093 .037 .411 .346 .308 .278 .187 .400 .337 .349 .247 .364 .337 .149 .109 .091 .290 .112 .048 .022 .132 129 6.4 .435 .488 .445 .126 .360 .320 .262 .173 .147 .135 .135 .086 .030 .165 .092 .129 .009 .724 .215 .201 .179 .141 .254 .259 .254 .208 .657 .161 .148 .135 .048 .220 .139 .137 .082 .696 .710 DEPTH (CH) 3.9 11.4 .111 .103 9117 .097 .107 .083 .032 .047 .154 .115 .117 .083 .077 .061 .059 .044 .759 .791 .087 .105 .084 .069 .045 .044 .001 .010 .123 .101 .069 .065 .033 .058 .059 .050 .753 .748 .174 .193 .137 .152 .120 .109 .068 907‘ .221 .207 .190 .153 .179 .172 .149 .131 .728 .729 .150 .151 .125 .122 .100 .084 .062 .059 .169 .151 .126 .125 .111 .091 .084 .079 .717 14.0 .106 .088 .061 .047 .121 .054 .056 .046 .756 .127 .035 .072 .037 .121 .082 .072 .042 .747 .209 .169 .125 .077 .230 .201 .186 .147 .712 .126 .096 .074 .050 .113 .075 .060 .056 .752 16.5 .133 .099 .065 .042 .105 .076 .059 .036 .763 .123 .085 .051 .036 .108 .094 .038 .032 .778 .262 .223 .106 .132 .271 .230 .198 .162 .594 .134 .093 .067 .054 .070 .045 .031 .038 9 769 19.0 .177 .125 .096 .076 .117 .063 .063 .059 .766 .125 .072 .046 .045 .114 .106 .045 .031 .795 .417 .345 .286 .229 .392 .321 .277 .233 .499 .117 .075 .048 .031 .068 .063 .040 .036 .792 APPENDIX 11. POT.. EVAP CN/DAY SITE. CORE TINE DAYS 53 oemszvv :e/cn3) 0.76 093 0 1. so 51 0'3 0 17 33 0.43 53 DEN§ITY GWflOvotDCDUHUCD\JQLc 5.0 691 CUM CuM FRAC EVAP EVAP CM .000 _.050 .094 _w.147 .18. .230 .264 .298 .363 .430 .492 .560 E bubJIACNOHHNHUFHHF*PCDO<3c: ACNPW?‘JUHD‘JNMDON&J‘<)O(flc3 091 CU-‘1 EVAP c9 ., (HOGMIONHURJPW‘fi‘PD‘CHDCDOHD OJ‘CJD(’JH‘ODOCdAH‘iJN\MOI0 CUM FQAC EVAP .000 .049 .086 .127 .158 .158 .213 .236 .281 .326 .368 .9418 .455 .493 .522 .552 .591 5.7 H21 C) Cl 3 EVA? C) 3 Fa - ‘ _ar. UCdOWUINO‘NWUNJHJ‘F‘HW‘CHOI: O O C O O O O O O O O O O O O D O 1 V\B&CNPW3\JWRJO‘HUHUCH}O\O It A ' . ‘ 4 I CUM FRAC EVAP 9000 1-9104 .118 ..183 .232 .284 .321 .355 ..413 .463 .509 .555 ;.586 .616 ’-.638 ‘.661 .687 5.3 0'1 CUH CUH FRAC EVAP EVAP CM 0.0' .000 0.3. .093 0.6 .162 0.8. .241 1.0 .292 1.2, .346 1.3} .333 1.5; .420 107' .492 1.9. .557 2.1 .617 203; .678 2.5. .717 2.61 .757 2.7_ .784 2.81 .811 2.9‘ .540 3.5 K91 CUM CUM FRAC EVAP EVAP CM 0.0 .000 0.4. .072 0.81 .143 1.3.-.222 1.6 .276 2.0. .334 2.2 .372 2.4. .405 2.7 .456 2,9_ .497 3.2 .531 3,4 1566 3.5 .589 3.6 .613 3.7 .629 3'8 .6‘9 4.0 .672 5.9 E'l CUM CUM PRAC EVAP EVAP CM .000 £1.032 .063 . .099 .125 ,,.152 .173 .,.193 .233 .270 . .306 ,_.348 .330 1.411 1435 W460 3.493 ‘V 1-4 “‘ ft finkOHUCdOHVhJNtfiwudhtoc3c1o MCDGHDGdHWNJIO'H\n0H‘ 2” ”32413 .>_ xficzm114 [ p . s _ a o, J ma 7 o¢~ mafia ovm Odfia; com mnww Dem noww Dem mna1. oqm nfim. 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