INFLUENCE OF THE BRSTERN GOTTONTAIL ON THESE REPRODUCTLQN 2% SUGAR'MAPLEBEECH STANDS C’F SEEUTHERN MICHIGAN Thesis for the Degree of M. S. MICHIGAN STATE UNWERSHY JOHN BEATTY MATHIES 1957 LIBRARY “a Sllll‘h‘l [cm I‘llll llll H 8 5 5 5 2 0 .I m i i \ m \ mm \ W \ Wu: \ WW ‘ University v 10 \ "’3 a“ 3 5 ‘.‘ ‘5 L133." 0 91??) ABSTRACT INFLUENCE OF THE EASTERN COTTONTAIL ON TREE REPRODUCTION IN SUGAR MAPLE-BEECH STANDS OF SOUTHERN MICHIGAN by John Beatty Mathies The study objective was to examine the cottontail rabbit as an influent on tree reproduction in an old-growth and a second-growth woodlot located near East Lansing, Michigan. Within each woodlot, four areas were selected that gave a range of the rabbit pressure observed in the woodlots. A total of lh72 seedlings of eight species was sampled by random strip transects within each area. These plants were measured in the fall and winter for height, age, and prior rabbit utilization. These same plants were subsequently rechecked in the spring for the current winter's utilization and mortality. The 1965-1966 winter study period was mild and became an important factor in reducing the use by rabbits in both woodlots below that anticipated. The winter utilization of the tree seedlings was examined to determine the percent of seedlings utilized by the cottontail prior to, and during, the study. Species preferences were similar in both woodlots. American beech, elm, and American basswood were preferred. Sugar maple and black cherry appear to be moderately accepted, whereas bitternut hickory, white ash, and northern red oak were non-preferred. Area preferences appeared to be directly related to the amount of available low ground cover. Past utilization on all species was similar in both woodlots, instead of decreasing in the old-growth woodlot John Beatty Mathies as might be expected. This is apparently due to additional food and cover available in the agricultural areas adjacent to the woodlot. In addition, use by rabbits in the second- growth woodlot was not as localized as in the old-growth woodlot. This may indicate a more suitable habitat for rabbits in the former area. Since the cottontail has definite preferences for species and areas, rabbit utilization could be an important factor in the height growth of the seedlings in these woodlots. Sugar maple was the most common species found in both woodlots, and an intensive study was conducted to determine its response to rabbit utilization. Each plant was classified into one of three utilization categories by the number of times each plant had been browsed. The growth rates indicated that the utilized plants in the old-growth woodlot were taller than unused seedlings of the same age. The reverse was apparent in the second-growth woodlot. Based on the average age of the seedlings, it appears that rabbit utilization, on a per year basis, is lower in the old-growth than the second-growth woodlot. The implication is that sugar maple may respond according to the amount of utilization per unit time. At low levels of use, it is stimulated to greater growth whereas the reverse is true at higher levels of use. Sugar maple may therefore be a good indicator for estimating total rabbit utilization in sugar maple-beech woodlots similar to the study woodlots. INFLUENCE OF THE EASTERN COTTONTAIL ON TREE REPRODUCTION IN SUGAR MAPLE-BEECH STANDS OF SOUTHERN MICHIGAN By John Beatty Mathies A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Forestry 1967 ACKNOWLEDGEMENTS I am grateful to the following individuals for assistance throughout this study. To Dr. L. W. Gysel, of the Fisheries and Wildlife Department, for guidance in the selection of the study areas, furnishing trapping data, and for valuable review and criticism of the ecological portions of the study. To the following members of the Forestry Department:- to Dr. R. K. Hudson, for advice and suggestions concerning the format of the dissertation; to Dr. J. W. Wright, for advice concerning the design of the field data collection; to Mr. D. J. Gerrard, for the invaluable assistance given concerning all statistical problems, and for the use and modification of a computer program which aided considerably in the sugar maple analysis; and finally to Dr. G. Schneider, under whom this study was undertaken, for guidance and advice throughout the development of the study, and for critical reviews and discussions during the preparation of the dissertation. I am indebted to Michigan State University for financial aid in the form of a teaching assistantship in the Department of Forestry, and for providing needed supplies during the two years of the dissertation preparation. CONTENTS ACKN OWLEDGEJ‘UIENTS O O O O O O O O O O O O O O O O O INTRODUCTI CN 0 O O O I O O O O O O O O O O O O O 0 REVIEW OF LITERATURE. . . . . . . . . . . . . . . DESCRIPTION OF GENERAL AREAS. Study areas. . . . . . . Toumey Woodlot. . . College Road Woodlot Climate. . . . . Physiography . . Soils. . . . . Biotic factors . FIELD PROCEDURES. 0 O 0 O O O O O O O O O O O O 0 RESULTS AND DISCUSSION. . . . . . Stand description. . . . . . Stand density . . . . Overstory composition . Climatic influence . . . . . Rabbit population. . . . Available food (tree seedlings, 10 cm. in height). . . . . . . . Previous utilization of vegetation . . Cottontail tree species preference ofioooooo o 150 s . Cottontail woodlot area preferences . Utilization of sugar maple. . . . . . Implications of sugar maple utilizatio Utilization of associated species . Current utilization of vegetation. . . . 00:30.00. ECOLOGICAL IMPLICATIONS . . . . . . . . . . . . . SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . LITERATURE CITED. . . . . . . . . . . . . . . . . APPENDIX. . . . . . . . . . . . . . . . . . . . . VITA. O O O O O O O O O O O O O O O O O O O ‘0 O 0 ii . 3 .12 .12 .13 .IU .15 .15 .16 .17 .19 .19 .19 .21 .21 .26 .26 .31 .33 .61 Table IO 11 12 LIST OF TABLES General rabbit preference of tree species commonly found in the sugar maple-beech fOI‘QSt region 0 O O O O O O O O O O O O O I O Basal area per acre of all trees one inch d.b.h. and over, Toumey and College Road WOOdIOtS, 1965-1966 0 o o o o o o o o o o o 0 Average monthly air temperatures during 1960-1966 and deviations for the 1965-1966 study period at the Horticultural Farm, East Lansing, Michigan. . . . . . . . . . . . Average monthly total precipitation and snowfall during 1960-1966 and deviations for the study period 1965-1966, at East Lansing, Michigan . . . . . . . . . . . . . . Number of tree seedlings per acre (10 to 150 cm. in height) available as rabbit food within areas of Toumey and College Road Woodlots, 1966 . . . . . . . . . . . . . Tree seedling (10-150 cm. in height) utilization by the cottontail rabbit previous to and during the study period, Toumey and College Road Woodlots, 1965-1966 Cottontail rabbit species preference by woodlot and area, 1965-1966 . . . . . . . . . Cottontail rabbit area preference by tree species utilized in both woodlots, 1965-1966. Sugar maple data summary for both woodlots from November, 1965 to June, 1966 . . . . . . Analysis of covariance for sugar maple reproduction by amount of use category, 1965-1966 0 o o o o o o o o o o o o o o o o 0 Linear regressions for sugar maple reproduction, by use categories, in Toumey and College Road Woodlots, 1965-1966 . Expected utilization per year for tree seedlings by species, and species prefer- ence of the cottontail rabbit, 1965-1966. . . iii .2O .23 .2u . .28 .30 .32 .3h .36 .37 .39 .51 Table 13 1LL 15 16 17 18 19 2O 21 22 23 2U. 25 26 LIST OF TABLES (Continued) Analysis of variance for total seedling density in Toumey and College Road Woodlot areas, 1966 . . . . . . . . . . . . . Analysis of variance for seedling density by species groups in Toumey and College Road Woodlot areas, 1966. . . . . . . . . . . Analysis of variance for species preference of the cottontail in Toumey and College Road Woodlots, 1965-1966. . . . . . . . . . . Analysis of variance for area preference of the cottontail in Toumey and College Road WOOdIOtS, 1965-1966 0 o o o o o o o o o o o 0 Analysis of covariance fer sugar maple reproduction in Toumey and College Road Woodlots, paired by use categories, 1965-1966 Bitternut hickory data summary for both woodlots from November, 1965 to June, 1966. . White ash data summary for both woodlots from November, 1965 to June, 1966 . . . . . . American beech data summary for both woodlots from November, 1965 to June, 1966. . Black cherry data summary for both woodlots from November, 1965 to June, 1966 . . . . . . Northern red oak data summary for both woodlots from November, 1965 to June, 1966. . American basswood data summary for both woodlots from November, 1965 to June, 1966. . Elm data summary for both woodlots from November, 1965 to June, 1966. . . . . . . . . Common and scientific names of plants discussed in the text . . . . . . . . . . . . Common and scientific names of animals discussed in the text . . . . . . . . . . . . iv Page ___:d_ .70 .71 .72 .72 .73. .7h .75 .76 .77 .78 .79 .80 .81 .82 LIST OF FIGURES Figure Page 1 Aerial photograph of the general study area and location of Toumey and College Road woodlots. I O O O O O O O O O O O 0 O O O .11 2 Monthly maximum snow depth during 1960-1966 and for the study period 1965-1966 at East Lansing, Michigan . . . . . . . . . . . . .25 3 Linear regressions for sugar maple in each study area in Toumey Woodlot, 1965-1966. . . . .hO A Linear regressions for sugar maple in each study area in College Road Woodlot, 1965-19660 0 o o o o o o o o o o o o o o o o 0 ‘ul 5 Sugar maple height-to-age relationship in Toumey and College Road Woodlots, 1965‘1966. o o o o o o o o o o o o o o o o o 0 014.3 6 Theoretical relationship of sugar maple response to the amount of rabbit utilization a plant receives . . . . . . . . . .N6 7 Aerial photograph of Toumey Woodlot and location of study areas. . . . . . . . . . . . .67 8 Aerial photograph of College Road Woodlot and location of study areas. . . . . . . . . . .69 INTRODUCTION The interactions between plants and animals have become an important field of ecological study. As man continually changes his environment, the disruption that is often created merely emphasizes his interdependence with the rest of the biotic community. The consequences of these disturbances are usually not recognized as being detrimental unless an adverse economic effect results. Man than attempts to correct his errors by, hopefully, restoring the ecological balance. Under pristine conditions, the Beech-Maple climax forest region encompassed a large portion of the Deciduous Forest Formation of the Lake States area (Braun, 1950).L/ A large part of this formation has been almost entirely removed or destroyed by logging and agricultural practices since the early 1600's. Approximately 0.1 percent of the original beech-maple area remains in a relatively undisturbed condition (Shelford, 1963). These stands are commonly small in size, and the animal constituents have been considerably altered. Certain species, such as the wolf, mountain lion, and elk have been eradicated; while other species, such as the whitetail deer and red fox, have invaded or increased in importance.§/ 1/ Common and scientific names of all plant species are given in the Appendix, Table 25. 2/ Common and scientific names of all animal species are given in the Appendix, Table 26. -2- The Eastern cottontail is one species that has apparently adapted by increasing its range and density as the continuity of the forest canOpy changed. This has been postulated from the facts presently known about the habitat requirements of the species (Lord, 1963; Fay and Chandler, 1955). This study examines the extent of cottontail utiliza- tion of forest tree reproduction in two contrasting sugar maple-beech stands in southern Michigan. Whereas the one area is a relatively undisturbed, old-growth stand, the other is a young, second-growth stand. Based on past and current utilization, the rabbit's preferences for tree species and area are determined, and resulting ecological implications are discussed. REVIEW OF LITERATURE The literature concerning rabbit use of woody vegeta- tion is both extensive and repetitive. The rabbit was first rec09nized as a farm, nursery, and orchard pest; and most of the articles prior to 1910 dealt with damage to agricultural crops. Damage to forest tree reproduction has only become important in studies since the early 1900's. The initial forest-oriented studies were primarily tabulations of the vegetation used by the rabbit (Aldous, 1936; Cox, 1936; Hendrickson, 1938; Smith, l9hO; Trippensee, 1938). Todd (1927) listed seventy-one plant species used by the cottontail rabbit. He determined this by following their tracks in winter and listing the species and portions of the plant utilized. His list contained thirty-one tree species but no indication was given of food preferences or the effect of use on the plants. Blair (1936) listed foods eaten by a captive Florida marsh rabbit for plants taken from its habitat. Seton (1929) stated that ninety-nine percent of the flora of the United States could be utilized by the cottontail rabbit. Lantz (1907) supports this statement although he was consid- ering arborescent plants only. It would appear that any list of plants used by the rabbit is of minor importance. (Perhaps the plants not used would be more important!) About l9h0 the emphasis shifted to food preference and numerous studies were made (Aldous, 19h7; Allen, 1939; Cook and Robeson, 19h5; deVos, 196h; Dice, l9h5; Dodds, 1960; Gammon SE 1., 1960; Lord, 1963; Pearce and Reineke, l9hO; -3- ‘LL‘ Sweetman, 19N9). Dalke and Sime (l9hl) determined food preferences from over thirteen hundred direct observations of feeding in Connecticut. They found seventy species of trees and shrubs utilized to some extent, with two species, gray birch and red maple, receiving the greatest amount of use. Although the method of preference determination was not stated, the listing of preferred foods differed from those receiving the greatest use, indicating unequal availa- bility. Food preference varied during the two years of the study, but no reason was given for this difference. Hough (19u9) studied the browsing of both the cottone tail rabbit and whitetail deer in a Pennsylvania hardwood forest. Rabbits were more discriminating in their browsing than the deer. All species were browsed approximately equally by deer but a preference for certain species was apparent for the rabbit. The rabbit preference was: 1) red maple, 2) beech, 3) sugar maple, and A) black cherry. A series of four inclosures were established to determine the effects of three types of browsing pressure on the vegetation. The increase in tree seedlings per acre was greatest when both rabbits and deer were excluded rather than if deer alone were excluded. The increase was large enough for the author to conclude that rabbits were more active than the deer in controlling tree reproduction. Hough stated that overp0pulations of either deer or rabbits were harmful to the vegetation. The rabbit apparently turns to woody vegetation when the herbaceous vegetation, forming its summer diet, becomes -5- unattractive (frozen or decayed) or unavailable due to scarcity, snow depth, or ice coverage (Sweetman, 19AM). When any of these conditions occur, the twigs and bark of woody plants become the primary winter food source (Allen, 1939). Nutrition apparently is a factor here since the consumption of woody vegetation involves more intensive digestive processes (Madson, 1963; Trippensee, 1938). Sweetman (19hh) found that the amount of injury incurred by woody vegetation was directly proportional to snow cover. This would indicate that weather, particularly snow depth, is an important factor to be considered when determining the cause and effect of winter use of forest reproduction by the rabbit. Numerous investigators have determined that most rabbit winter utilization occurs on hardwood species. While no agreement on the order of preference exists, there is general accord on preferred species compared to non-preferred species. Table 1 indicates the general rabbit preference for trees commonly found in the sugar maple-beech forest region. A few authors have noted winter rabbit utilization of conifers. Trippensee (1938) noted heavy damage on Corsican pine (probably Austrian pine) and Scotch pine with moderate damage to Eastern red cedar. Dice (19h5) reported damage on several pine and spruce species. The comparison of hardwood damage to conifer damage appears to be related to the habitat requirements of the cottontail. Allen (1939) gave the -6... habitat preference as follows: 1) cutover oak-hickory brush areas, 2) lowland brush thickets, and 3) young conifer stands. Lord (1963) found that the cottontail prefers an area with low ground cover rather than an Open area, and Gysel (1957) determined that the amount of use was directly related to the rabbit's preference for low ground cover. Table 1. General rabbit preference of tree species commonly found in the sugar maple-beech forest regioné/ Preferred species Non-preferred species American basswood Eastern cottonwood American beech Shagbark hickory American elm Sycamore Black cherry White ash Black oak White oak Black walnut Yellow pOplar Gray birch Ironwood Northern red oak Quaking aspen Red maple Sassafras Sugar maple a/ Dalke and Sime, l9hl; Gammon et al., 1960; Hough, 19h9; Lord, 1963; Pearce and—RETneke, l9hO; Sweetman, 19AM There are also indications that the rabbit has intraspecific preferences as well as interspecific prefer- ences. Moore (l9h0) found that planted seedling stock was utilized to a greater extent than natural regeneration. He postulated that this was due to the greater volume of growth made available by the planted seedling. Perhaps the nutritional content of the plant is also a factor. Sweetman (l9h9) found that succulent growth was more attractive to foraging -7- rabbits than old woody stems. He also found a preference for sucker or sprout growth over normal seedlings. Because browsed plants often remain within reach of the rabbits for a longer time, the same plants may be utilized for several years. These plants are subject to clipping until they grow out of reach or obtain a minimum diameter of one-half inch for portions of the plant still within reach of the rabbits (Dice, l9h5). The damage to larger plants is usually re- stricted to the removal of the bark. Although it may occur at any season, barking is more prevalent during severe winters and/or high rabbit populations (deVos, 196h; Miller, 1965). On small plants, the rabbit commonly cuts the stem near the base and then eats toward the tip of the cut material (Hutchison and Kotok, 19h2). Derr and Mann (1959) found that the damage often occurred on the stem about one- eighth inch above the ground level. Few investigators actually reported on the ecological effects of rabbit utilization upon the forest. Scholz (l96h), in a northern red oak stand, found that protected seedlings averaged seventy inches in height, while unprotected seedlings averaged fifty-four inches in height at ten years of age. The total effect was to retard tree growth one or two years and reduce tree height. Scholz suggests that the rabbit damage is cyclic in nature, being more severe during popula- tion peaks. The plants recover quickly, despite the amount of use, between the population highs. In contrast, Gammon ‘33 l. (1960) found that the average height of northern red oak Seedlings remained relatively unchanged, due primarily to rabbit browsing. Another rabbit influence which has received little study is the extent of plant mortality. The rabbit may be the cause for the scarcity of certain native shrubs. Sharp (1957) found that seedling shrubs were often killed by exces- sive rabbit browsing within two years following their germi- nation. Geis (l95h), in a study of black oak in southern Michigan, found cottontail damage on eighty-nine percent of 212 plants examined. The damaged trees had: ) a slower rate of height and stem diameter growth ) an increase in main limbs and dead main limbs per tree a higher incidence of heart rot ) ) their annual growth utilized for several years on many of the trees I 2 3 h As a consequence of this disturbance, Geis proposed that rabbit damage may be an important factor in the survival and perpetuation of oak as a dominant species in the stand. Similar results were found by deVos (196h), who studied the snowshoe hare in Ontario and found forty-four tree species browsed to some extent. He concluded that the hare may affect the plant composition of a forest stand. This is accomplished through the food preferences of the rabbit, resulting in a differential survival of the species in the stand. DESCRIPTION OF GENERAL AREAS The study was conducted in two woodlots within five miles of the Michigan State University campus at East Lansing, Michigan (Figure 1). The first of these, Toumey Woodlot, was acquired by the University in 1939. It is a relatively undisturbed, old-gnowth sugar maple-beech stand, one of the few remnant stands of this forest type in the area. The fifteen acre stand is located in the NE l/u of the SE 1/u of Section 30, T hN, R 1w, Michigan Meridian in Ingham County, Michigan. The stand has not been grazed, burned, or logged (except for removal of a few dead and dying trees for firewood) during the known single ownership which was established in 1852. The area is presently surrounded by agricultural crops on the west, pastures on the north and south and a county road on the east. The stand is being maintained as undisturbed as possible for continuing forest research. The second area, the College Road Woodlot, is located about one and one-half miles south of Toumey Woodlot. It is a second-growth sugar maple-beech stand with ample evidence of recent selective logging throughout the area. The history of this forty-three acre stand is unknown, but it has probably been grazed and there are indications of past wildfires in the area. This woodlot is located in the SW l/h of Section 6, T 3N, R IN, Michigan Meridian in Ingham County, Michigan. 'The area is presently bounded by an interstate highway on the north, and by agricultural crops on the remaining sides. -9- -10- Figure 1. .Aerial photograph of the general study area and location of Toumey and College Road Woodlots (Scale: 1 inch = 3000 feet; April 9, l96h) N College Road u I .l I —. wt), ~.. \ u. - .. . u.( . . n .. v. n... .i I.“ .~ y u - .. . - .HVPP.....1 a... 33.3%....» FAWN... . - ...i h. .. p ‘A 1.3 no . c . r . . .11”?an 'IHorticultural Farm -12- Study areas Toumey Woodlot.--Four areas were selected in this woodlot as representative of the range of winter utilization by the cottontail rabbit. Two of the areas having low use were located along the north and south borders of the woodlot (Figure 7). The woodlot edge paralleling the north area, and adjacent to a pasture, was relatively open. Protective ground cover within the north area was noticeably sparce, with a few dead trees on the ground. The south area afforded more suitable cover than the north due to the remnants of an old wooden fence, and the high grass cover in the adjacent unused pasture. A small abandoned triangle of. land is located between the woodlot and the present fence at one end of the south area and provided additional cover for the south area. The other two areas chosen represented locations of intensive rabbit utilization as evidenced by the high degree of browsing in both the blowdown and the swamp areas. The swamp created an oblong opening which was surrounded by a relatively dense herbaceous plant cover during the summer. In winter, this provided some cover, as did a few old blow- downs within the area. The sample area was located along the northwest edge of the swamp within 150 feet of a small stand of planted red pine. In l96h, several dead and dying American elms were felled and left on the southeast edge of this intermittent swamp. The blowdown area was the result of a local windstorm, -13- which occurred in September, 1959. Both uprooted trees and broken stems created an opening approximately a quarter acre in size. Common elderberry rapidly invaded the site and apparently provided a highly suitable habitat for the Cettontail since it became a center of rabbit activity during subsequent winters. College Road Woodlot.--The four areas selected in this woodlot were comparable to those in Toumey Woodlot (Figure 8). The north area was located adjacent to an old clearcut area presently covered with a dense stand of staghorn sumac. Whereas few actual tree stems were found on the ground, several brush patches offer nearby protective rabbit cover. An abandoned cornfield and a small plantation of Scotch pine are within 300 feet of the area. The south area was located near the eastern boundary of the woodlot proper. A wire fence parallel to this area provided some protective rabbit cover. The woodlot area east of this fence was heavily logged and only a few scattered young or cull trees were left standing. A dense cover of herbaceous and shrub vegetation dominated the ground cover and tree reproduction was sparce. Brush piles, created primarily by logging slash, were found throughout the area. The swamp area was located on the northwest edge of the swamp and had less downed logs than found in Toumey Woodlot. The sapling segment of the tree reproduction was more dense than any other area. The area was within 200 feet of an abandoned cornfield and a patch of staghorn sumac. -1u- The blowdown area was apparently an old logged area with subsequent blowdowns along the perimeter. Most of the merchantable material was removed but several piles of tops and cull 109s were left. A dense herbaceous ground cover predominated over the area, with grass cover along an old logging skid road. Climate The climate is considered strongly continental with relatively variable temperatures. Normal daily air tempera- tures range from a maximum of 8hoF. to a minimum of 12°F. Extremes of 1020F. and -25OF. have been recorded at the EaSt Lansing station. Total precipitation averages 31 inches a year, with an average of 23.1 inches occurring during the study period of September through May. The precipitation is fairly evenly distributed through the year, with lows of 1.8 and 1.7 inches in January and February respectively, and highs of 3.7 and 3.3 inches in May and June respectively. Average snowfall is 55 inches a year and occurs normally between October 20 and May 1. The extremes in total snowfall were experienced in 190h-1905 when 18 inches fell, and in the 1925-1926 winter with 8h inches. Winds are generally moderate to mild, averaging seven miles per hour annually, with west and northwest winds pre- vailing during the winter and more variable winds, generally southerly, during the summer. The average growing season is 1&6 days, with a recorded range of 106 days minimum to 195 -15- days maximum (Baten and Eichmeier, 1951; Barrett, 1962). Physiography The area is characteristic of the glacial deposits throughout the region. The reconstructed history of the area begins with a Tertiary Peneplain which was uplifted and then eroded over a long period of time. Several periods of glaciation followed, and the present depth of the glacial drift is around 300 feet in the general area of the study, with the elevation averaging 800 to 900 feet above sea level. The topography is gentle with rolling hills and little stream dissection. Drainage is to the west, through the Red Cedar and Grand Rivers to Lake Michigan (Barrett, 1962; Leverett, 1917). Soils The soils are predominately well-drained mineral soils of the Gray-brown Podzolic great soil group. In Toumey Woodlot, Hillsdale and Spinks loams are found through most of the woodlot, with Conover silt loam predominating in the low swamp area (Schneider, 1966). College Road Woodlot differs in that the primary soil type is Miami loam, changing to Spinks loam in the blowdown area, and Conover loam in the south and swamp area.§/ 3/ Tri-county soil survey, Soil Conservation Service, East Lansing, Michigan. Personal communication, 1966. -15- Biotic factors Although the cottontail rabbit was the animal studied, other animals are commonly found within the woodlots. Evidences from tracks, scat, trapping results, and direct observations indicate that the following mammals inhabit the study areas: Shorttail shrew Fox squirrel White-footed mouse Woodchuck Meadow vole Racoon Southern bog lemming Opossum Starnose mole Red fox Eastern chipmunk Whitetail deer FIELD PROCEDURES The study of four selected areas within Toumey Woodlot began in Fall, 1965. Four additional areas within College Road Woodlot were chosen in March, 1966. As far as possible, these were similar to corresponding areas in Toumey Woodlot in tree seedling composition and extent of previous rabbit utilization. Initial reconnaissance of both woodlots indicated that species density was too low to be effectively sampled by use of permanent mil-acre plots. Therefore, a series of random strip transects were established, oriented parallel“ to the border of each area where possible. Since the blow- downs were circular in outline, they were sampled by random strip transects passing through the center of the blowdown area. Depending upon species frequency, from five to twelve strip transects were established in each area, with the average size being two feet by fifty feet. All species were sampled as they occurred throughout each transect except for sugar maple in Toumey Woodlot. Because of the great abundance of sugar maple throughout this woodlot, randomly selected strips of thirty consecutive mil-acre quadrats were established to insure that a representative sample of each study area was indeed obtained. These quadrat strips were also parallel to the adjacent forest border, and each quadrat was located with a small wooden stake. Where present, a suitable number of sugar maple were sampled in each mil-acre plot, with the plants nearest the investigator -17- -18- selected upon entering the plot. A total of lh72 plants of eight species were sampled‘ in both woodlots. Each plant was marked with a strip of yellow, plastic coated, adhesive tape. The species symbol and sample number were written on each tape with a black felt tip marker. The tag was placed within two inches of the base of the tree to minimize the experimental effects on the rabbits, as snow and dead leaves would help cover the tags. All trees sampled were measured for height, age, and amount of winter use by rabbits. A maximum height of 150 centimeters was used to limit the sampling to the size normally used by the cottontails (Geis, 195h; Pearce and Reineke, l9h0). Height of the present live leader was recorded to the nearest centimeter. Age was determined by either counting the actual terminal bud scars, or estimating those portions where bud scars were not discernable. Previous use by rabbits was recognizable from other mammal use by the characteristic h50 angle of shearing and smooth face of the cut (Scholz, 196h; Todd, 1927). The utilized stems are persistent for several years after they have been clipped and the samples were divided into three levels of rabbit use: 1) not used, 2) used once, and 3) used more than once. The areas were examined at one or two week intervals during the winter to determine the extent of rabbit use occurring throughout the study period. The final field work in both woodlots was completed in June, 1966. Each plant was rechecked for winter use and mortality resulting from rabbit use. RESULTS AND DISCUSSION Stand description The amount of cover has been found to influence the habitat favored by the cottontail (Allen, 1939; Gysel, 1957; Lord, 1963; Miller, 1965). During the winter months, the available rabbit cover in a deciduous forest is often diffi- cult to define. The general description of each woodlot was previously discussed. In addition, tree density and species composition were sampled to aid in the description of each woodlot area. Stand density.—-For convenience, this will be termed the "overstory" and includes all trees over one inch d.b.h. (diameter at breast height). Although this is a broad classification, it serves as an overall description of the present stands. Toumey Woodlot has been the subject of a continuing ecological study since l9h0. The woodlot has been subdivided into sixty-foot square compartments and an inventory has been completed on all stems one inch d.b.h. and over (Schneider, 1966). Total stand density in 1965 is shown in Table 2. This is an old-growth stand typical of the few remnant sugar maple-beech stands in this area. Stand density is high, with basal area per acre between 113 and 193 square feet. The College Road Woodlot has not previously been studied. The overstory density was determined by examining -19- -20- three randomly selected plots in each area of the woodlot using the variable plot method and a ten-factor prism (Grosenbaugh, 1958). This information is summarized in Table 2. Table 2. Basal area per acre of all trees one inch d.b.h. and over, Toumey and College Road Woodlots, 1965-1966 WEBdlot ‘Aaea l Basal area per acre Toumey a/ North 193 South 160 Swamp 1 18 Blowdown 113 Average 157 College Road b/North 60 South 110 Swamp 90 Blowdown 57 Average 79 a Based on 100 percent inventory. Based on averages of three variable plots. As can be seen, the College Road Woodlot is considerably less dense than Toumey Woodlot. In fact, the densest area sampled in College Road Woodlot has three square feet of basal area per acre less than the least stocked area found in Toumey Woodlot. This second-growth woodlot has had a considerable volume of its merchantable sawtimber removed. -21- The remaining stems are thus small and the majority of the stand's basal area is therefore in the small sawtimber size class. A few scattered large cull trees, often beech, are also present. Overstory composition.--Species composition in Toumey Woodlot is primarily sugar maple, with some beech and elm distributed throughout. Although a total of twenty-two tree species occur in the woodlot, only eight appear in any abundance. The College Road Woodlot contains much less sugar maple than Toumey Woodlot for all areas except the south. Sugar maple comprises but one-half as much basal area as found in Toumey Woodlot; whereas three species, white ash, black cherry, and elm have twice as much basal area as in Toumey Woodlot. This woodlot is younger and the species composition includes a greater number of the less typical species which are commonly found in the successional stages (Shelford, 1963). Climatic influence Several authors have noted that the amount of rabbit use of woody vegetation varies with the depth of snow, or the severity of the winter (Allen, 1939; Dice, l9h5; Dodds, 1960). To examine this climatic influence, the weather during the study period was compared to the average weather conditions for the past six years. All weather data is from the Horticultural Farm located on the Michigan State univer- sity campus at East Lansing, Michigan (U. S. Weather Bureau, -22- 1960-1966). This station is located about one-half mile from Toumey Woodlot and two and one-half miles from College Road Woodlot. The air temperature data are presented in Table 3. In general, the 1965-1966 winter, though considered mild, had temperatures below average in November, January, April and May. The temperatures in December and March were notably higher than the averages for those months. The late winter and early spring period is often the most important to rabbit survival. The rabbits normally go into the winter with a layer of fat, and this source of energy is depleted as the winter progresses. As the winter of the study was relatively mild, the amount of rabbit utilization observed in the woodlots was apparently reduced. Total precipitation and snowfall data are shown in Table A and Figure 2, respectively. Precipitation was uh percent higher than the average, with a total precipitation for the study period of 22.10 inches as compared to the past six-year average for that time period of 15.38 inches. The only month having considerably less than average total precipitation was January. Conversely, snowfall was less than expected for all months except January. Total snowfall was 16.7 inches compared to the average of 28.1 inches, a hl percent reduction. A.most significant weather factor influencing rabbit browse was the amount of snowfall in the late winter and early spring period. The premature decline in measurable snow depth, two months earlier than usual, greatly contributed to the reduced rabbit use observed on -23- 0.0+ -.m0 :.-0 0.0- -.0m 0.0m m.0+ -.-: 0.0: 00eae>< 0.0- 0.-: 0.0: m.0- -.:0 0.-0 0.0- 0.00 0.00 00: 0.0- 0.00 0.00 0.0- -.:m 0.00 m.- 0.0: 0.0: -aa< m.0+ 0.0m m.0m 0.0+ 0.0: m.0: 0.0+ 0.00 0.00 00002 0.-+ 0.0- 0.0- -.-+ 0.00 m.m0 m.-+ 0.0m -.:m 00000000 m.- 0.m- 0.0- 0.0- 0.0m :.0m -.- 0.0- 0.-m 0000000 0.0+ 0.0m m.0- 0.0+ 0.0: m.00 0.0+ -.:0 m.0m 00050000 0.0- o.m0 0.m0 0.0- -.0: 0.0: 0.0- 0.0: :.-: e0050>0z 0.0- m.-: 0.-: 0.0- 0.00 0.00 0.0- 0.00 0.00 .-00300 0.0+ 0.mm 0.-m 0.0- 0.00 0.00 -.0- m.00 0.00 000200000 mmmem>m ommum>w ammum>m 8000 000A 000A 8000 000A 000A 8000 000A oood domwmwbm -HmooH 1bmoH Commmu>mm-lm000 .ibon scammfi>ma Immofl 1000A A.mov EsEHcAE mmwco>< A.mov Ezefixme owmpm>< A.mov manpmpmmamu mmmem>< cucoz cmchofiz .mcumcmq ummm .5000 “masgflsoflpcom one um 600000 xvspm wood-moqfi 0:0 000 wcofiumfi>on 6cm ooofiiooofl mcfipnu mmuauwuoasou paw AficucOE mmmem>¢ .m mfinmh -2“- 00000000 00000 60600000 0:02 00 0.-- 0.0- 0.00 m0.0+ 00.00 00.0- 000000 - - - - - - 0-.0- 00.0 00.0 00: 0.0- - 0.0 m.m- - 0.0 00.0+ 00.0 00.0 -000< 0.0- 0 0.0 0.0- 0 0.: 00.0+ 00.0 00.0 0000: 0.0- 0.0 0.00 0.0- 0.0 0.0 00.0- -0.0 00.0 00000000 0.0- 0.0 0.0 -.-+ 0.0 0.0 00.0- 00.0 0-.0 0000000 0.-- 0.0 0.0 0.0- 0.0 0.0 0m.m+ 00.0 -.0 00000000 0.0: 0 0.0 0.01 0 0.0 on.H+ 0o.m wm.~ 00nE0>oz " I- '| I' O 4 O 0 ("w 0 U 0 \m0 0- 0+ om - 00 0 0 0 0 - - - - - \m- 00.m+ 00.0 00.0 000200000 ImmflrUCHw. 00000>0 00000>0 00000>0 8000 0000 0000 5000 0000 0000 8000 0000 0000 undo: co0000>0a 1m00~ 1000" aofluww>0m umoofi nooofi so0000>0o Imoofl 10000 £0000 30:0 EdEAxmz “AmazoCm 5030:02 :000000000000 00000 20003002 .mcfimcma 000m 00 .oooH-mooH 000000 20000 0:» 000 meofiumfi>00 0:0 woofiiowofi 0:0000 Hfimgzocm 020 Co00000000000 "0000 aficucos 00000>< .: 00000 -25- 00000002 .0000000 0000 00 000-m000 000000 30:00 000 000 000 0000-0000 000000 00000 30:0 E0E0x0s 00:0C02 000% 0:0 00 00:0: >0: 00< 00: 000 C00 o0o >02 000 .N 000000 00w H H h V//////// V///////// Y///////////// F 00000000 00000 n .w ooofiimowfi Hm QQOHIOQOH u D o OH NH (saqou; uI) qqdap mous papJooaJ mnwyxew -26- the study areas (see Table 6). Rabbit population While no information on the rabbit pOpulation exists for the College Road Woodlot, trapping studies have been occasionally conducted in Toumey Woodlot since 1958.E/ Fall trapping was for periods of up to one month in August, November, and December; whereas spring trapping was conducted in April and May. Both wooden and woven-wire box traps, baited with corn, were used. Prior to each animal's release, sex and age information were taken and the animal was tagged with aluminum ear tags if it had not been trapped previously. Success varied considerably over the six-year period. A.maximum of fifteen different individuals was trapped in the Fall of 196h; the minimum of zero trapped occurred several times prior to this same date. However, the relia- bility of cottontail trapping data has been severely criticized in recent work (Eberhardt E: 31., 1963). For this reason the data has been used to indicate general trends only. The rabbit population in Toumey Woodlot was relatively stable in 1958 and 1959, and appears to have been increasing since 1963. Available food (tree seedlings, 10 to 150 cm. in height) One measure of available food is the density of vegetative reproduction in the area. To determine the density of the tree seedling reproduction, five mil-acre Q/ Gysel, L. W. Personal communication, 1966. -27- plots, representative of the average stand conditions, were randomly established in each woodlot area and the total number of stems by species were recorded for plants within the above height restriction. The average species densities per acre by woodlot area are shown in Table 5. The same species occur in both woodlots, but in varying amounts within each area. An analysis of variance indicates that the total species density is not significantly different between either the woodlots as a whole, or for the four areas sampled within Toumey Woodlot (Table 13). The areas selected in College Road Woodlot are also similar except for the south area. It appears that this significance is perhaps due more to the lower species density found in the blowdown area rather than the higher density in the south. Therefore, with this one exception, study plots within and between both woodlots are similar when total tree seedling density is considered. This similarity, however, does not hold when individ- ual tree species density is examined. An analysis of variance revealed a significant difference between woodlots when the density of sugar maple and the collective density of all other species is compared (Table 1h). Toumey Woodlot is composed primarily of sugar maple with a scattering of other species. .Although sugar maple is also the most common species in College Road Woodlot, it has a significantly lower density of sugar maple and a higher density of all other species. This indicates a change in species composition of -28- 0000 :000 :0 00000 00001008 0>0000:0000000 0>00 :0 0000m 000800 :0 0:00000 002 “W 0 0.00 0.: 0.0 :.o m.m 0.0 0.0 0.0 0.0N 00000>0 0000000 0.00 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0- 00000>< 0.0 0.0 - 11 11 - - -1 0.0 03003000 0.00 0.00 - 0.0 0.0 0.0 0.0 0.0 0.0 0:030 0.0: 0.0 - - 0.0 - 0.0 0.- 0.00 00000 0002 0.00 0.00 0.0 0.0 0.0 - 0.0 0.0 0.0 00002 0000-00 0.00 o.N 0.0 :.o 0.0 11 0.0 0.0 :.0N 0m000>¢ 0.00 0.0 - - 0.0 - 0.0 0.0 0.00 03003000 0.00 0.0 - 0.0 0.0 - 0.0 0.0 0.00 00030 0.00 0.0 0.0 0.0 - - 0.0 0.0 0.00 00000 0.00 - - 0.0 - - \m- 0.0 0.00 00002 000000 # 00030000 :00 000 >000:0 :0000 :00 _ >00000: 00008 000000 Sam :00000E< :0000002, 0000m.:00000E<-000:3u00:00000 000:0 000d. 0000003 000< b“ A0000 000 00:00:00» :00 0000:00 0000000 14 00000 .00000003 000m 0000000 0:0 508000 00 00000 :0z003 0000 000000 00 00 0000>0 .000000: :0 .80 omH 00 000 0000 000 00:000000 0000 00 000502 .m 00000 -29- the tree reproduction between the young second-growth College Road Woodlot and the old-growth Toumey Woodlot. Previous utilization of vegetation The number of utilized plants found in the woodlot is an indication of the winter rabbit pressure, and this factor is directly related to the amount of use an area receives. An attempt to evaluate these conditions is summarized in Table 6, which shows the percent of previously utilized tree seedlings found in each study area. This percentage is indicative of the total use observed during a period of years in which the evidence is persistent. The value may be slightly misleading since the damaged stems do not remain on the plant for a constant period of time before either decay, healing, or mechanical disturbance removes the evidence. However, if it can be assumed that these effects are found equally in all the woodlot areas, then the trend of percent utilization can be compared for each area. The areas vary in their intensity of utilization with the greatest amount of use having occurred in the blowdown area of Toumey Woodlot. While utilization varies from O to 100 percent, the average previous use observed for all areas and species was 68.8 percent. It should be noted that the extent of observed utili- zation in each area of Toumey Woodlot differed noticeably from similar areas in College Road Woodlot. Two areas that differed considerably were the north and the blowdown areas in College Road Woodlot. Some of these differences may be Tree seedling (IO-150 cm. in height) utilization by the cottontail rabbit previous to and during the study period, Toumey and College Road Woodlots, 1965-1966 tiArea [ Toumey —North Prev. Table 6. -—»<———.¢ __j Area [average eriEanfETm asswood Am b f ern oak North red ,1 Black ash‘ beech cherr Percent utiTTEEtion by species [White Amer. itternut hickory [ Periodl '8 Sugar maple Woodlo NO NO \00 O O 25 0 Curr. South Prev. (ID-3' 04~ .d'v—a 10 "*0 mm U\ 00 O\-—+ 5 Curr. OO 00 d. 83.0 0. Curr. Swamp Prev. 0 O 95 2 Blow— Prev. down Curr. -30- mf’) (\J\O CDN [\K") (13H NO 0‘0 \0 6 Curr. Aver- Prev. age (”)0 H 100.0 O-fl' O‘C’) O 0 8LL Curr. 9 South Prev. College North Prev. Road 00 00 In Curr. mo NO Curr. Swamp Prev. 0 5.0 Blow— Prev. down Curr. CON HCO O\-:l‘ \01!\ [\1—0 NCO CO-d' 6 Curr. Aver- Prev. age CON (Em \O 85.01 15. (Dc—4 O\CO 66. 2. Prev. Curr. averages Species Not present in sample 2/ -31- due to the selection of the areas. The north area in College Road Woodlot provided more available cover than did the corresponding Toumey Woodlot north area, and was also adjacent to a dense staghorn sumac thicket. It is therefore possible that the rabbit population was higher there than anticipated, resulting in greater previous use. On the other hand, the blowdown area had less previous use than the comparable blowdown in Toumey Woodlot. Here, a dense grass and herba- ceous plant cover apparently has resulted in a very low density of tree reproduction (see Table 5). During the winter, when the annual plant cover has been flattened, suitable rabbit cover is considerably reduced. Cottontail tree species preferences.--An analysis of rabbit preferences for tree species was performed, based on previous utilization, with species preference compared by ranking percent use within each area (Table 7). Species preferences are significantly different (see Table 15), with only three of the eight species sampled preferred by the cottontail, when based on a mean rank value of b.08. These were American beech, elm, and American basswood, in that order. Two species appeared to be intermediate in preference. These were sugar maple and black cherry. The remaining three species appeared to be avoided to some extent by the cotton- tail. In descending order, these were bitternut hickory, white ash, and northern red oak._ A paired "t" test was performed to see if the prefer- ences varied between the two woodlots. The only species .Hcommca mum noan meowaw mmocu com AHcO mH mcchwu HmHaEmw CH ucwmwpa uoz \m .mocm chu cog N u n + Aw + m + 0v no .mmHowam 66H“ Ho confide ecu kn tmcH>Hu mxcmc 66pmsh6wwca may go 85m on“ mH xcmc pHHam cap .COHumNHHHH: pcmocwa mm :HHZ moHomam swung mm: mmpm coco: Awssoh "mHamem .mosHm> cwHH pom cw>Hm cum mxcwc HHHam \m mocmcmmmca mchmmcomv muonvcH meshes: m>Hmmmoosm 6cm CoHHmuHHHH: Hamocoa Hmmcch mcp mmumoHocH H mo xcmp < .mmcm pmcp canHz mchcsooo mmHomam comm Ho coH mNHHHH: bamocma on» an mmum uoHUOQB comm 60H .m ou H Eocm .vmxcmn cum mmHooam w no.2 wn.m no.m m©.m no.2 Hm.H m~.m om.m mm.: xcma cam: 0mm OH «3H «mm fin «m o: «Hm do Hmuop moHowam m m z o H m N m wmmaw>< _ m u- -- a H -- -u m czoaonm w m «H «a j «H o «a m aawzm . N II m d H N o m Epsom vmom m a m o m m N m couoz ammHHoc N o w d H w m m ommuo>< H II II N II : \Mtl m CBOvZOHm m l- a m H o a m QEmsm m a a m H o m m cpsom m m a \ma H n : a aHaoz amazes 6003mmmn xmo cop xpcmzo comma 5mm zpoonz oHawE EHm cmoHcmE< dcmzbcoz xomHm cmoHcosd opch unaumHHHm ummsw moc< HoHnooz fill - -\MmmHume powlquxcwu mocmuomoum r IA booHumboH .mmcm 6cm HoHUOOB ho wocmummmca mcHooam uHanmu HHchouuou .5 mHnmh -33- that differed significantly between the two woodlots was bitternut hickory. This species was preferred to a greater extent in Toumey Woodlot than in College Road Woodlot. Although the other species had a wide range in preference values between woodlots, the differences were not significant. Species preference was not directly related to seedling density. However, because sugar maple occurs in such great abundance, it comprises the greatest percentage of the cottontail diet for the eight species sampled in the woodlots, although it is but a moderately preferred species. Cottontail woodlot area preferences.--To determine if certain areas were preferred over others, the areas were 1 ranked by the amount of use each species received. The results, in Table 8, and evaluated by analysis of variance in Table 16, show a significant difference in the utilization occurring between the eight areas sampled. Three areas appeared to be preferred over the rest when based on a mean rank value of h.00. These were the Toumey blowdown area, College Road north area, and the Toumey swamp area in that order. Three areas used moderately were the College Road swamp area, Toumey south area, and the College Road south area. The final two areas appeared to be avoided more than any other area. These were the Toumey north area, and the College Road blowdown area. This difference in area Prefer- ence is apparently related to the amount of low ground cover in the immediate area where the use occurred (see pages 12 through in). -3g- .HCowoua mmHomam chu cuHB mwocm among pom zHcO wH mcchmu moHaEmm cH “Cowman H02 \m .mmHomam mHnu com «3 u N + Hm + :v no .mmmcm 06H“ mo accede 63H >9 060H>H0 waMc nmumshvmopa may mo Sum can mH xcmc uHHam map .coHHmNHHHH: Hcmonma No :HHS mmmcm 03» mm: mHamE cmmsm «mHamem .mmsHm> 06H“ com am>Hm 6cm mxcmc HHHaw \m .oodocmmmua mcwamuomv mcHaonccH mcmoESC m>Hmmmoosm nHHB .mmHooam own» no“ aoHumNHHHps pcmopma uwmcmHz wzp.:uH3 muum HoHuooz map mmumochH H No xcmp < .HCwmmpa mH muHomam “map 606:3 mmmcm may do CoH mNHHHH: Hcmocua 650 ha .mmHomam 5006 now .m on H Sock umxcmc mum mmocw HoHnooz m 00.: no.0 00.: 0m.: mN.m mN.H 00.0 0H.: NH.m acme awe: 0Hm «0m mm 00 mm N :m «00 H: Hayes mwa< N 3 m N H m o m compo>m mou< 0 0 0 wH «H N m : EH0 u: H II N n: I: m : 0003mwwo cmoHcoE< I: m N H II J m o xmo cop cumzupoz 0 a m m H m 0 N seamen somHm «0 m0 «a m0 I- «0 «0 N 00000 cmoHame< .. m N 0 «0 «0 m H cam mchz -- 0 m 0 \m-- H m : Naoona sscamosHm N m: \Mmd N H m o w oHawE ummsw —:30030Hm asm3w_zpsom npuoz‘I—czononm asmzm endow cocoz_ moHomam _ uoHnooz 000m mmmHHoo — uoHcooz mosses _ 000Hum00H .mpoHnooz coon :H umNHHHHs mmHooaw coca >n mocmumwmca «mum aHnnmp HHchOHHoU .m mHnmN -35- Utilization of sugar maple.--The most common species found in both woodlots was sugar maple. One hundred randomly selected seedlings were sampled in each woodlot area for height, age, amount of rabbit use, and mortality. A summary of the results is given in Table 9. To determine the response of sugar maple to rabbit utilization, an analysis of covariance was computed to determine if the height-to-age ratio was correlated to the amount of winter use (Table 10). Three use categories were used: 1) not used, 2) used once, and 3) used more than once. The analysis for Toumey Woodlot indicates that for the average of the four areas sampled, the growth rates for the three use categories are not the same. This probably indi- cates the site difference in the woodlot. However, when each area within the woodlot is considered separately, the growth rates for the three use categories are constant within each area. The effect of use can then be determined by the difference among the regression lines and is indicated in Table 10. The north area of Toumey Woodlot does not differ among the various use categories. This was also the area with the least amount of use of any area sampled. As winter use rates increase, the difference in growth is more easily detectable among the three use categories. At about fifty percent use within a woodlot area, this difference in the growth rates is statistically significant. For the woodlot areas that had different regressions, an analysis of covari- ance was used between pairs of use categories to determine wamuw>w 0.m m.m :00 m.Nm H60 0.0 H 0.0 0.NN H N6: 000 flame $050 0.0 0.: .010: 0.0m. 0.2., 0.0 ...... 0.m 0.00. H 0.0: 00: 00803 0.0 0.m 0.00 0.NN 0.m: 0.m H :.: N.0m .+. 0.00 02 6.8320 0.0 0.0 gm... 0&0 0.00 m.m H :0 0.NN H 0.0m 00H aewzm 0.0 0.m 0.:: 0.0m 0.3 m6 H 0.0 :.mm H 1:0 00H 525 m 0.0 0.0 0.0: 0.mm 0.0H m6 H H0 m.Hm H H.mm 02 £82 wmeHHcmo 0.: 0.0 m.0m 0.va m.:0 :.: H 0.0 H.0m H H.N: 00: 00803. 0.0 0.m 0.NN 0.0H 0.m 0.H H 01m 0.00 M :0m 02 c3855 0.0 0.0 0.0: 0.3. 0.NH 0.: H m.N 0.NN H 0.5 00H 9:85 0.0 0.H 0.8 0.00 0.1: 0.: .+. m0 m.mm H H.H: 02 5:8 0.N 0.0 0.0 0.0H 0.mN 0.: H H.0H :.Hm H H00 02 5:82 .853 summocmau nucwopwau Ibcmocmal nmcwwkn 1.80: oflWo coco 06m: NHHHchoz mm: bomb, mam: uoz mum oanoc uoHaEmm mwc< HoHvooz acmppso mm: mon>mpm mmmpm>< mmmpm>< confisz .mm‘oocov~>wl oboH .ocsw o» mbmH .cmosm>oz Souk wuoHvooz soon now humEESm mama uHawE uwmsw .o oHnmh -37- was 00:00:: mmbaoHacH Swap 0H0» obstHaEm :H cmmmHv mocHH conwmcmmc .HmHHmcma mum mmcHH ecu NH .pcmonHcanICOC 0H EmHHwHHmcmaucoc awn: chO HsgmchmmE mH mconmmpmmp macaw mocwpummHQ \m HmHchma boa mum mucHH may :02» mammE moconchme .mm uommpmo mm: HHw pom mmcHH Conmmpmmp 02p mo mmaon 0:0 mpmmw EmHHmHHmcma:oz m 0H.A Q:00.0 H00.v. 0:00.mm ammam>< mm0.V0vH0. N0m:.: 000.V0VH00. m0:0.0 czoaonm 0H.A mmmHH 0H.A :0mH.m 050.30 H00.v. :m:N.0H H00.v. mm00.mm c0000 0HrA 0HNm.0 H00.v 0000.0 00002 0000 000HH00 HAX%nv 0:00.N00 000.V0vH00. 000:.0 000002< H00.v H0:0.N 0H . A 00mm; 03003on H00.v N000.HH Hz..A mNm:.H 00030 m0.vnHme0. 0000.0 0H.A n00N0.H 5:00 0H.A 000m; 2 . A :momd 5.82 @560 locmocmau ‘ Ipdmocmal , , - suHHammnpuml. 00Hm>r _ spHHHnanoum _ msHm>l — mma< poHaooz \Mmconmwpmop mcoEm oococmmmHQ _ \MEmHHwHHmcmaucOz H lllll Ni pcsoEm kn coHuosvouawu oomHumooH .znomoumo om: mo wHamE pmmsm Low oocmem>oo mo mehHmc< .oH mHnmN -38- where the significance was in the system. Although the alpha level is not 0.05 percent in doing this, the results are used to indicate the amount of significance attributable to each comparison (Table 17). In general, there was little growth difference between the unused plants and the plants used once. The greatest height change occurred between the plants used more than once and the other two categories. In the College Road Woodlot, only the swamp area had a constant growth rate for the three use categories. It was similar to the north area of Toumey Woodlot in that the height-to-age relationship indicated no difference in ampli- tude among the regression lines. In general, the growth 0 rates, for each woodlot area, were stable for all use classes in Toumey Woodlot, while no consistency was shown for the College Road Woodlot. The second-growth woodlot was much more variable in the height-to-age relationship as well as in the overstory composition and continuity. A linear regression analysis was conducted to plot the regressions for each woodlot area, with the regression analyses corresponding to the significant categories as determined by the analysis of covariance in Table 10. The results are shown in Table 11 and Figures 3 and h. In general, the rabbits in Toumey Woodlot appear to be utilizing the rapidly growing seedlings more than the older or slower-growing seedlings (see Figure 5 and Table 9). Two alternatives are possible: either the rabbits occupy the more productive tree growth sites, or the plant utiliza- -3g- wcHH 20H0000mm0 000 km 00% 000250060 0Q 206 0000 moc0H00> 0:0 00 paeo0wa 000 &m mode 20:0 0008 000: n HA 6cm “wocO 0003 u H 0000: 002 o \0 0000. 000:.0- 0NNH.0 000.V0vH0. 000N.0 H0 -A 0000.HH 00::.0- N:0:.0 H00.v 00N0.0H 00 H 0300 0:00.0H 00N0.0- 00::.0 H00.v N000.00 0: 0 -30-0 0000.N 0000.N 0000.0 H00.v 00H0.00 00 HH< 00030 :000.0 N000.H0 HHNH.0 00.V0V000. 00N0.0 0: -A 0000.0 000:.00 N0H0.0 0-.A HN00.0 H0 H N:00.: 0:00.0 0000.0 H00.v 0H00.0H H0 0 00000 0000.: 0000.0 0000.0 H00.v 0NN0.0N N: HA H000.: 0N00.0 00:0.0 000.V0vH00. 0H00.0H 00 H 0000 0000.: 0000.0 HNHH.0 0H.n 0N00.H :H 0 00002 000HH00 00N0.0H 0000.: 0000.0 H00.v N000.00 0N HA :H00.0H HHHH.00- :000.0 H00.v 00:0.:0 0- H 0300 0000.N 0000.0 N:00.0 0H.A 00H0.0 0 0 -30-0 0000.0 00N0.0 0000.0 H00.v 0:0H.N: 0: HA 0000.0 0000.0H 0:00.0 H00.v 0000.N0 00 H 0N00.0 N00H.0 :0:0.0 000.vmvH0. 0H00.0 0H 0 00030 0:00.0 0000.H0 N000.0 H00.v 0000.00 -0 0A :00:.H 0000.:0 0000.0 0H.A 000H.0 :0 H 0000.H 0H00.0H 0000.0 0H.A 0H0:.0 00 0 00000 0000.0 00H0.0 000:.0 H00.v 00H0.00 00 HH¢ 00002 0H02000. NSHNNV :Q: NSHNKK 3m: \MM AHCNULQQV EOUNer'H \m X0 + 0 u > 00000000000 z0-H-000000 00H0> 0 00 000 00 000< 0000003 0H580om Conmm0mwm donmmummm :onmm0mmm mmmpmmm omnmmfl 000Hnm0oH .mpoHcooz 0000 wmeHHoU 000 008000 CH .mmH0ommpmo mm: 0n .26H005000am0 mHamE 000:0 0cm wconww0mm0 pwwcHa .HH mHan -u0- 60 60 ’3 '0 ‘— L: Q) N '3 ‘3 5&0 Combined 5’40 4-, 4-, a c Q) 0) o o 5 a V 20 V20 4-, +3 a a C) CD 0 "5 :1: I: A. NORTH B. SOUTH 00 5 10 0o 5 10 Age (in years) Age (in years) 60 H. ,0 >1 m m \- L. L- k1 0) Q) +3 4-} Q) Q) 5 5 no \0 +9 +3 c c m w o o 5 .5 0 0 20 n n O) U) 0 '3 3: 3: C. SWAMP D. BLOWDOWN O0 5 10 O0 5 10 Age (in years) .Age (in years) a/ O = not used; 1 = used once; >1 = used more than once Figure 3. Linear regressions for sugar maple in each study area in Toumey Woodlot, 1965-1966 _u1- 6O ,- ,- 0 U) (D L. {- 3 .93 ,1 E _ 200 «.4 .F. 1 I: *5 I Q) Q) U U c c V V 20 +3 4-) 0 n U) U) 0’ 50’ A. NORTH O B. SOUTH 0o 5 10 o 5 10 Age (in years) Age (in years) 60 6C Combined X m ’3 La La 0’ 0) H 4-, gm g LLC H 4-) c c Q) Q) o o c c V20 V 2c 4-, +3 c 0 U) U) 0 ”0'3 x I C. SWAMP D. BLOWDOWN O O S 10 O 5 10 Age (in years) Age (in years) a/ O = not used; 1 = used once; )1 = used more than once Figure A. Linear regressions for sugar maple in each study area in College Road Woodlot, 1965-1966 -Ag- tion by the rabbit results in a stimulation effect on the seedlings themselves. The first alternative is probably not a factor since both the greatest and least amount of utilization occur on the same soil type within six hundred feet of each other. The second alternative is more difficult to ascertain. Theoretically, if site and heredity factors are similar in an area, all trees should be growing at approximately the same rate. Therefore, potential rabbit use can have one of three effects on a tree seedling. If the rabbit's utiliza- tion of sugar maple is truly random, there could actually be a stimulation effect on the plant. 0n the other hand, if the rabbits did indeed select the faster growing seedlings, then equal growth rates would reflect a detrimental impact since they would have been growing at an even faster rate if not utilized by the cottontail. If the seedlings did not respond at all, then the utilized plants would show a reduced growth rate and height at the same age as the unused seedlings. In Toumey Woodlot, the north, south, and blowdown areas are all on predominately the same soil type, so that tree growth rates should be similar on the basis of site alone. The blowdown area has a higher plant growth rate than either the north or south areas, the result of increased light and reduced competition. The swamp area also has a high tree growth rate, apparently due to a better water supply during the growing season. The data indicates that the growth rates are not significantly different among the -u3- 60 E m ()Swamp E 50 4..) 5 ‘4‘Toumey o 0 :MO +College OSouth g Blowdown' Road 0 North CD "0 C . South Q) .North 07 {2’30 Q) > m (i) 0‘ 520 0: Area in Tourney Woodlot :3 O= Area in College Road g Woodlot (D -F= Mean of the woodlot LL 6 8 10 12 Average age (in years) Figure 5. Sugar maple height-to-age relationship in Toumey and College Road Woodlots, 1965-1966 ~Mh- used and unused seedlings, but the used plants are taller than the unused seedlings at the same age. This can apparently be attributed to two factors operating in this woodlot. The rabbits appear to select the more rapidly growing seedlings, and this utilization subsequently results in a stimulation of the seedling growth. However, the reverse of this occurs in the College Road Woodlot, since the utilized seedlings are shorter and are growing at a reduced rate when compared to the unused seedlings. Implications of sugar maple utilization.--Numerous studies have shown that seedling growth and survival are influenced by many factors such as: Seedling density Seedling age Overstory competition Soil fertility Water availability Microenvironmental conditions Species vigor Biotic influences (ENO‘U'l-F'CANH Any one or a combination of these factors could result in the height-to-age differences observed in the two sampled woodlots. I propose that the cottontail may be an important biotic influence in woodlots such as those examined. It is known that the cottontail will re-use the same seedlings (Sweetman, l9h9). The number of sugar maple utilized by the cottontail was nearly identical in the two woodlots sampled. Based on current seedling utilization (Table 6), it appears that cottontail pressure is lower in the old-growth woodlot -Ag- than in the second-growth woodlot. If this is in fact true, then it appears that the amount of use per unit time is lower in the old-growth than the second-growth woodlot. This also appears to be true for seedlings which may not be re-used, and is indicated by the older age of the seedlings in the old-growth woodlot. If the seedlings are used randomly by the cottontail, then the same reduced utilization per unit time is indicated by the similar utilization and older age of seedlings in the old-growth stand. When the linear regression analysis is considered, it appears that cottontail use has resulted in greater growth of the utilized seedlings in the old-growth woodlot, whereas the reverse was observed in the second-growth woodlot. ‘ From these observations, the proposed relationship for sugar maple response to rabbit use is shown in Figure 6. A similar relationship has been observed in range management for browsing by domestic animals (Sampson, 1952). There would appear to be a threshold level of utilization where sugar maple growth is not different from an unused seedling. For Toumey Woodlot, the apparent location is to the left of the threshold level, resulting in a stimulation of seedling growth. College Road Woodlot would be located on the right of the graph, producing a detrimental effect on seedling growth. Although this effect would vary in degree for different sites, it is possible that this type of rabbit influence would occur in other similar woodlots. m0>H0o00 HamHa m :00000HHH0: “Hanmu 00 025050 0:0 00 00:00000 0Hame 00m00 No aHzmcoHHmH00 HmoHp0000CH .0 00:0H0 Alllll.0EH0 0H0: 000 CoHumNHHHpb :mHm 00000002 30: 0002 -Ag- 00H0003 000m 0m0HHoU s H - ll: - / a / / v / H / HH / -__,L \ l O z 0 00H0003 008500 / uamoufi iufiteq uo eouanIJuI \1 H0>0H 0H000000e -u7- Sugar maple may thus be a good indicator of winter rabbit pressure in a woodlot of this type. Although over half of the trees sampled were sugar maple, the percent utilization by the cottontail (Table 6) closely approXimates the average use for its respective area and is the only species of the eight sampled that is not significantly different from the area average. Other factors support the choice of sugar maple, such as the low to moderate preference for sugar maple (neither avoided or overly pre- ferred), longevity in the available height class (oldest average age of the eight species sampled), and ease of obtaining sufficient samples. Utilization of associated species.--In addition to sugar maple, seven other species were sampled in the two woodlots. The results are summarized in Tables 18 through 2h in the Appendix. Stocking levels for these species were low and therefore insufficient data were available to perform an analysis similar to that completed for sugar maple. In general, data for these species supported the sugar maple results. Only one species differed greatly, that being northern red oak. Although this species was the youngest in age and shortest in height of the eight species sampled, it was both older and taller in College Road Woodlot than in Toumey Woodlot, the reverse of all other species. The oak was also much more preferred by the cottontail in College Road Woodlot than in Toumey Woodlot. It is possible that this reversal in the height-to-age relationship is an -145- expression of the same theory postulated for sugar maple. Since the oak was the least preferred of any species in Toumey Woodlot, there would be minimal stimulation from rabbit use. In contrast to this, the oak in College Road Woodlot received moderate use and may have resulted in greater growth. However, the reduction in height of the northern red oak appears even greater than can be accounted for by just age reduction alone. It may also indicate that this species is perhaps more sensitive to damage than the other species sampled. The elm also differed slightly from the generally observed pattern. The age was about equal in both woodlots but the height was shorter in Toumey Woodlot. The amount of use, both previous and current, was much greater in College Road Woodlot. This is also possibly explained by the stimulation effect noted earlier. Current utilization of vegetation The utilization of tree seedlings that occurred during the study period by the cottontail is shown in Table 6 as the current use. In all cases, the current use is less than the total previous use. Utilization ranged from O to no.6 percent of the sample when each species is considered separately within the specific woodlot areas. This compares with a range of O to 100 percent for previous use. Species averages for all areas range from a minimum of 1.6 percent utilization for white ash to a maximum of 15.5 percent for the elm. This compares to a previous use of 55.1 percent -h9- for white ash as the minimum, and 96.9 percent for American beech as the maximum. The areas also vary when all species sampled within each area are combined. Two areas in Toumey Woodlot, the north and the swamp areas, had minimal utiliza- tion of 0.6 percent while the College Road north area had the maximum of 17.1 percent utilization. This area had noticeably more utilization, over three times as great as the next highest area. This compares to a minimum previous utilization of h2.2 percent in the Toumey north area, and a maximum of 93.9 percent in the Toumey blowdown area. Of interest here is the question: can the rate of utilization experienced during any one current winter be used as an estimate of the rabbit pressure within that area? One approach involves determining an average rate of‘ utilization experienced on the area during previous years, and then comparing the current winter's utilization to this previous use average. This estimate is made by dividing the average age of the plants into the total percent of utiliza- tion. It is recognized that many variables are not taken into consideration in obtaining the average utilization for a species. Some of the more important variables are: Varying populations of rabbits Unequal availability of food species Differences in the volumes utilized by species Variable weather conditions during previous years Agricultural practices on adjacent lands Competition with other species for the same foods OW-F‘CANH Therefore, while the average utilization is only a guide, it does reflect the annual use experienced over the -50- period that the plants have been present on the area. These estimates were calculated and compared to the current utilization experienced in the combined woodlot areas (Table 12). All species received significantly less than the average annual utilization for the current 1965-1966 winter as determined by Chi square analysis. Only two species were within ten percent of the average annual utilization, all remaining species having less than half their respective averages. This supports the conclusions of the climatic data by indicating a mild winter with little demand for woody vegetation. It is interesting to note the species preferences as determined by the average annual utilization. These values compare favorably with those indicated by the mean rank values determined previously in Table 7. This would further imply that the age of the reproduction is an important consideration in determining the species preference. Secondly, it is proposed that by observing the amount of browsing on several key plant species, a man in the field would be able to estimate the pressure or number of rabbit "use-days" occurring within an area. This approach would involve a random sampling of a suitable number of each key species for cottontail utilization, and determining the average height and age of each species. To obtain such an estimate of rabbit pressure, the following would need to be determined: 1. The parameters which would affect the use of a species, such as snow depth, temperature, unequal availability of tree species, age differences, growth differences, and adjacent cover. -51- m 0000H 00 00000 0005 5000 00>000Q :N 0m00000 w0 000 0 000009 8000 00>000Q 0 00009 8000 00>000Q 7hi317h N m N I m.m0 0.00 N0.m o.m© 80m 0 0 00. 0.0 0.00 00.: 0.00 noozmmmn 0000000< m m w I m.00 ®.:0 mq.m 0.wm x00 000 00000002 0 0 :m- 0.0 0.00 00.: :.00 000000 00000 0 0 :0- 0.0 0.00 00.0 0.00 00000 e0000me< 0 0 mm- 0.0 :.00 00.0 0.00 cwm 00003 0 : 00- 0.0 0.00 00.: 0.00 0000000 0:0000000 : 0 00- 0.0 0.0 :0.0 0.00 00000 000:0 10000000: :0000%1 I000o000| \0 \m \0 0000000000 000% 00a 000o0ax0 000 000% 000 000 00000000000 m00o0am 000 .>000 E000 0000 00000000000 0m000>< mso0>000 000000w l 0000 0000000000 somwmwmmm nmwmm. wsofiwwmmri. 000mm-z:;_ 1 ooqfinm0q0 .000000 0000000000 000 00 0000000000 0000000 000 .0000000 >0 000000000 0000 000 000% 000 00000000000 000000xm .NH 0000H -52- 2. The number of species to sample. 3. Which reproduction species give the most reliable index of use. Ecological implications I. 'The composition of the overstory has an important influence on the seedling composition within a stand. It is recognized that seed production, germination requirements, and tolerance levels vary between species. It should also be recognized that the biota can significantly influence tree seedling composition. The present study was not exten- sive enough in either time or area to fully examine this influence, but it appears that the cottontail has had an. effect on past tree seedling composition. The two dominant tree species of the study areas, sugar maple and beech, reflect this influence. Although sugar maple comprises 10 to 80 percent of the overstory in each study area, the reproduction ranges from 25 to 98 percent of all tree seedlings. In all areas, the percent of seedling reproduction is greater than the overstory percent for sugar maple. In contrast to this, American beech comprises a lower segment of the seedling reproduction than found in the overstory in all the woodlot areas. The species preference analysis indicates that beech was the most preferred Species, while sugar maple was fourth preferred out of the eight species sampled (see Table 7). II. The change from a second-growth to an old-growth woodlot is an important influence on the cottontail. As the stand matures, the available rabbit cover is often reduced -53- and as a consequence rabbit pOpulations are diminished. This was not found in comparing the two woodlots in this study. The average percent damage in the old-growth woodlot was within five percent of the second-growth woodlot (see Table 6), indicating that the total utilization is roughly similar. The percent use is an index of the rabbit pressure per unit time, and it is possible that the populations and/or pressures in the two woodlots are similar. This leads to the question: what factors allow the rabbit pressure to be maintained in the old-growth woodlot at a level similar to the second-growth woodlot? It would appear that food and cover are primary considerations. Associated with the reduction of rabbit cover in an old-growth woodlot is a similar loss in available food, primarily in the herba- ceous plants utilized by the cottontail (Moseby, 1963). If both the food and cover are reduced within the old-growth woodlot, then these limitations are being met by the adja- cent lands providing sufficient food and cover to maintain a higher rabbit pressure. If winter cover is not limiting, the consequence would be an increased winter utilization of woody vegetation in the old-growth woodlot, such as was found in Toumey Woodlot. This woodlot is surrounded on three sides by either agricultural crOps or pastures, as well as planted conifers on the woodlot edge, a swamp and the blowdown area; all of which probably contribute to the available food and cover requirements of the cottontail. -5u- It is postulated that the break-up of the forest continuity is exemplified by the maintenance of a greater rabbit pressure throughout the life of small isolated forest stands. This appears to be one of the more important biotic changes that can be attributed to man's interaction with the pristine sugar maple-beech climax forest. SUMMARY AND CONCLUSIONS This study examined the biotic interactions between the Eastern cottontail and tree reproduction under two sugar maple-beech stands in southern Michigan during the winter of 1965-1966. Toumey Woodlot, an old-growth stand, was selected as being typical of the remnant stands of this type. In contrast, College Road Woodlot was a second-growth stand with evidence of much greater disturbance than Toumey Woodlot. Factors considered in determining the cottontail influence in these areas were: the climate during the study period, available estimates of the rabbit populations, tree reproduction and overstory densities, and the current as well as past rabbit utilization of sugar maple reproduction and seven other associated tree species. Stand description Analysis showed that species abundance and stand density were different between the two woodlots. Toumey Woodlot is primarily composed of sugar maple and beech, with twenty other tree species, of which only six are common, scattered throughout the woodlot. Basal area per acre was higher in the old-growth woodlot, with the densest area sampled in the second-growth having a lower basal area than the least dense area in the old-growth woodlot. College Road Woodlot is composed primarily of sugar maple, along with considerable amounts of elm and white ash. It has had a -55- -56- considerable portion of the merchantable timber removed, and the majority of the stand's basal area is in the pole and small sawtimber size classes. Climatic influence The 1965-1966 winter was mild. Temperatures were generally higher than normal, total precipitation for the September to May period was an percent above the six-year average, but snowfall was hi percent below the average. Snow depth attained a maximum of six inches in December, with measurable snow depth also observed in January and February. The decline in the snow depth was two months earlier than expected, and was considered an important factor in the low amount of browsing observed in the woodlots. Available food (tree seedlings, 10 to 150 cm. in height) The density of tree seedlings was used as a measure of woody vegetation available as food for the cottontail. Although the same tree species occur as reproduction in both woodlots, their density has been altered. While the total seedling density remains the same for both woodlots, the old-growth woodlot has lost a large number of its less common tree species, and this void has been occupied by additional sugar maple. Previous utilization of vegetation The percentage of utilized tree seedlings is an indication of the winter rabbit pressure, influenced by the winter weather severity. Both woodlots have experienced -57... similar previous utilization, with an average of approxi- mately 69 percent of all sampled tree seedlings having been utilized prior to the study. A. Cottontail tree species preferences. Based on previous rabbit utilization, the following species prefer- ences were observed: Preferred 1 .Accepted Non-preferred American beech Sugar maple Bitternut hickory Elm Black cherry White ash American basswood Northern red oak These preferences were consistent in both woodlots except for bitternut hickory. This species was preferred more in‘ the old-growth than the second-growth woodlot. While indivi- dual Species preference was not related to the available food, the total species utilization within an area would be more closely related to the available food. Sugar maple would comprise the bulk of the cottontail diet in both woodlots. B. Cottontail woodlot area preferences. The blowdown and swamp areas of Toumey Woodlot had much greater previous use than the other two areas sampled in that woodlot. The use in the second-growth stand wasn't as localized as in the old-growth woodlot, indicating that it provides an over-all environment more conducive to rabbit use than the old-growth woodlot. Two areas were noticeably avoided. The north area in Toumey Woodlot apparently lacked suitable ground cover. The -58.. College Road blowdown area similarly had a minimal ground cover during the winter period and was used less frequently than any area in this woodlot. The amount of winter ground cover apparently is an important influence of the rabbit population utilizing the area. C. Utilization of sugar maple. Whereas the utilized seedlings in College Road Woodlot have a reduced growth rate compared to the unused seedlings, those in Toumey Woodlot were taller than unused seedlings of the same age. If the rabbit utilization of sugar maple is truly random, then the utilized sugar maple appear to be stimulated to produce more growth than an unused seedling. The Opposite would be true if the cottontail actually selected the faster growing seedlings. If equal growth rates occur for both used and unused seedlings, then this would indicate a reduction of the potential growth of the utilized seedlings. D. Implications of sugar maple utilization. It appears that sugar maple responds pr0portionately according to the amount of browsing the plant receives. At low to moderate levels of use, sugar maple is stimulated and produces greater growth than it does without any use. At more intensive levels of use, the effect is detrimental and either death or a reduced growth rate results. Sugar maple appears to be a good indicator of the winter browsing pressure in a woodlot. Compared to the other species sampled, it remained within reach of the rabbits for a longer period of time, thus providing a longer -59- record of use. It also was the only species sampled that gave an accurate estimate of total utilization within the woodlot areas. Current utilization of vegetation About five percent of all tree seedlings sampled were utilized during the 1965-1966 winter. This winter had less than average use and supports the general belief that winter severity influences the amount of utilization of woody vegetation. Species utilized to the greatest extent were elm and northern red oak. These Preferences are not the same as indicated by the data for previous utilization. While species abundance varies from year to year, this may also indicate that food preferences vary from year to year. There is also a possibility that the age of the tree seedlings is an important consideration in determining species prefer- ences o Ecological implications The two predominant species of this forest type give an indication that the cottontail may have an influence on seedling composition. Sugar maple is forming an increasing proportion of the seedling density while beech reproduction is decreasing. Beech was the most preferred species in the woodlots while sugar maple was moderately preferred. The change from a second-growth to an old-growth stand also has an influence on the cottontail. As a stand approaches the climax type, the available food and cover is often reduced. In an extensive stand of this forest type, -50- this would normally result in a reduced rabbit pOpulation and/or pressure. It may be that in small isolated stands such as Toumey Woodlot, it is the adjacent areas that provide sufficient food and cover to compensate for the loss within the woodlot. This would then permit an increased winter pressure on the woodlot by the cottontails from the adjoining areas 0 LITERATURE CITED Aldous, C. M. 1936 Food habits of Lepus americanus phaeonotus. Jour. Mamm. 17: 175—176. Aldous, Shaler E. l9u7 Some forest-wildlife problems in the Lake States. U. S. Forest Serv., Lake States Forest Expt. Sta. Paper 6, ll pp. Allen, Durward L. 1939 Michigan cottontails in winter. Jour. Wildl. Mgmt. 3: 307-322. Barrett, John W. (ed.) 1962 Regional silviculture of the United States. Ronald Press, New York, 610 pp. Baten, W. D. and A. H. Eichmeier 1951 A summary of weather conditions at East Lansing, Michigan prior to 1950. Mich. State Coll. Agr. Expt. Sta., 63 pp. Blair, W. Frank 1936 The Florida marsh rabbit. Jour. Mamm. 17: 197-207. Braun, E. L. 1950 Deciduous forests of eastern North America. The Blakiston Co., Philadelphia, 596 pp. Cook, David B. and Stacy B. Robeson l9h5 Varying hare and forest succession. Ecol. 26: hoe-hie. Cox, W. T. 1936 Snowshoe rabbit migration, tick infestation and weather cycles. Jour. Mamm. 17: 216-221. Dalke, Paul D. and Palmer R. Sime l9ul Food habits of the eastern and New England cottontails. Jour. Wildl. Mgmt. 5: 216-228. Derr, Harold J. and W. F. Mann Jr. 1959 Guidelines for direct—seeding longleaf pine. U. 8. Forest Serv., Southern Forest Expt. Sta., Occas. Paper 171, 22 pp. deVos, Antoon l96h Food utilization of snowshoe hares on Manitoulin Island, Ontario. Jour. For. 62: 238-2hh. -6l- -62- Dice, Lee R. 19h5 Some winter foods of the cottontail in southern Michigan. Jour. Mamm. 26: 87-88. Dodds, Donald G. 1960 Food competition and range relationships of moose and snowshoe hare in Newfoundland. Jour. Wildl. Mgmt. 20: 52-60. Eberhardt, Lee, Tony J. Peterle and Raymond Schofield 1963 Problems in a rabbit pOpulation study. Wildl. Monog. 10, 51 pp. Fay, Francis H. and Edwin H. Chandler 1955 The geographical and ecological distribution of cottontail rabbits in Massachussets. Jour. Mamm. 36: hl5-u23. Gammon, A. D., V. J. Rudolph and J. L. Arend 1960 Regeneration following clearcutting of oak during a seed year. Jour. For. 58: 711-715. Geis, Aelred D. 195h Rabbit damage to oak reproduction at the Kellogg Bird Sanctuary. Jour. Wildl. Mgmt. 18: MES-h2h- Grosenbaugh, L. R. 1958 Point sampling and line-sampling: probability theory, geometric implications, synthesis. U. S. Forest Serv., Southern Forest Expt. Sta., Paper 160, 3h pp. Gysel, Leslie W. 1957 Effects of silvicultural practices on wildlife food and cover in oak and aspen types in northern Michigan. Jour. For. 55: 803-809. Hendrickson, George 0. 1938 Winter food and cover of Mearns cottontail. Trans. N. Amer. Wildl. Conf. 3: 787-793. Hough, A. F. l9h9 Deer and rabbit browsing and available winter forage in Allegheny hardwood forests. Jour. Hutchison, C. B. and E. I. Kotok 19h2 The San Joaquin experimental range. Calif. -53- Lantz, D. E. 1907 The rabbit as a farm and orchard pest. U. S. Dept. Agr., Yearbook of Agr., 1907: 329-302. Leverett, F. 1917 Surface geology and agricultural conditions of Michigan; Part II, The southern peninsula. Mich. Geol. and Biol. Survey Publ. 25: 103-215. Lord, Rexford D. Jr. 1963 The cottontail rabbit in Illinois. Illinois Dept. of Cons., Tech. Bull. 3, 9h pp. Madson, John 1963 The cottontail rabbit. Olin Mathieson Chemical Corp., 56 pp. Miller, William E. 1965 Protecting Christmas tree plantations. Jour. For. 63: 8h9-852. Moore, A. W. . 19h0 Wild animal damage to seed and seedlings on cut-over Douglas fir land of Oregon and Washington. U. S. Dept. Agr., Tech. Bull. 706, 27 pp. Moseby, Henry S. (ed.) 1963 Wildlife investigational techniques. Edward Bros., Ann Arbor, u19 PP. Pearce, John and L. H. Reineke 19h0 Rabbit feeding on hardwoods. U. S. Forest Serv., Northeastern Forest Expt. Sta., Tech. Note 35, 3 pp. Sampson, Arthur W. 1952 Range Management principles and practices. John Wiley and Sons, New York, 570 pp. Schneider, G. 1966 .A twenty-year ecological investigation in a relatively undisturbed sugar maple-beech stand in southern Michigan. Mich. State Univ. Agr. Expt. Sta., Res. Bull. 15, 61 pp. Scholz, Harold F. 196M Seeding and planting tests of northern red oak in Wisconsin. U. S. Forest Serv., Res. Paper LS-7, 7 pp. -6u_ Seton, Ernest T. 1929 Lives of game animals, Vol. IV. Rodents, Etc. Doubleday, Page and Co., Garden City, New York, 781-815. Sharp, Ward M. 1957 Management of a poletimber forest for wildlife food and cover. Pennsylvania.Agr. Expt. Sta., Bull. 620, 26 pp. Shelford, V. E. 1963 The ec010gy of North America. Uhiv. of Illinois Press, Urbana, 610 pp. Smith, Charles C. 19h0 Notes on the food and parasites of the rabbits of a lowland area in Oklahoma. Jour. Wildl. Mgmt. u: 429-u31. Sweetman, Harvey L. 19MB Selection of woody plants as winter food by the cottontail rabbit. Ecol. 25: M67-h72. 19u9 Further studies of the winter feeding habits of cottontail rabbits. Ecol. 30: 371-376. Todd, John B. 1927 Winter food of cottontail rabbits. Jour. Mamm. 8: 222-228. Trippensee, R. E. 1938 Food relationships of the cottontail rabbit in southern Michigan. Trans. N. Amer. Wildl. Conf. 3: 79h-80u. U. S. Weather Bureau 1960-1966 Local climatological data for Lansing (East). U. S. Govt., Superintendent of Documents, Monthly reports, var. pp. APPENDIX -65.. Figure 7. Aerial photograph of Toumey Woodlot, and location of study areas (Scale: 1 inch = 130 feet; Jan. 12, 1965) V§Z v u. b .4 . h t . r ‘ l O U .n ‘ N . . 0.00.0000000000000000000 0’ O . .. C ‘ . o . - , O ,. I 0000.00.00.00...100000.000 .. 000 I v» .. \rh. . .. plsl ‘ . .. .. I! W . bl. New _ Ct. 900‘. ‘| A ‘. ‘ VI .1 . do 00 co b . .. 4 r' . O o . vl. . 0* , . o. no .. m ‘ It) 1‘ . . .. .1 0 v .N O o r d «a. 49. o o . . . W o"‘ i C I; k .\ \JI . . . ... “b . o 1 ma. . . a. 1 vs .1 e... . 0.. b B « u I AJ.’ a o . O o O I i. s. . - 0 o o . .a T O . I '0” 40 «(m C . ..O C ”4 C . a C C Q -68- Figure 8. 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I‘V‘III' 0000 000000 0000003 000m 0000000 000 008000 00 000000 0000000 >0 0000000 00000000 000 0000000> mo 000000c< .00 00000 -72- Table 15. Analysis of variance for species preference of the cottontail in Toumey and College Road Woodlots, 1965-1966 Source EDegrees of 2 Sum of: Mean sum.[ F : Probability freedom squaresi of squares value (percent) Species 7 131.326 18.7609 6.99118 (.001 Error A6 123.378 2.6821 Total 53 25u.70u Table 16. Analysis of variance for area preference of the cottontail in Toumey and College Road Woodlots, 1965-1966 Sou e : Degrees of: Sum of; Mean sum * F ProBEBIIIty TC freedom squaresf of squares value (percent) Species 7 73.360 10.u800 3.2700 .OOSr_eowHewasoo eee< eeHeooz Nmmconwopmmp Cmmzuon oocwpmgmHo fl \lEmHHoHprnmucoz— opoHnmomH .mmeommpmo mm: kn umpHma .wuoHuooz 000m ommHHoo 0cm koEsoh CH :oHuosuouaop mHamE pmmsm pom mocmem>oo mo mHmkac¢ .NH mHan -7u- mHaEwm CH “common #02 \m 0.0 0d 0.0m 0.00 0.00 m.m H H.HH H00 H :d: 00 éwmwflmuewsfiepfim 0.0 0.0 0.NN 0.00 0.0: m.H H 0.0 0.0m H 0.00 mm 002800 in I: It nu In in: :1: o c3003on 0.0 0.0 0.0 mém m.m0 0.0 H 0.H 0.: H H.0H 0 0530 0.0 0.0 0.0 mém m.0m 0H H 0.m .HH.0H H 0.0H 0H 5000 e 0.0 0.0 0.00 0.H0 0.H0 H.H H 0.: 0.00 H 0.0m 0m 5.82 0meanch 0.0 0.0 0.00 :00 0.00 0.0.“ 0.m 0:00 H 0.3 00 00323 n: u: In I: u: nun \MIun o c30030Hm 0.0 0.0 0.2 0.2. 0.00 0.0 H m.m 0.00 H 0.00 2 02030 0.0 0.0 0.0m 3.3 0.00. 0.0 H 0.: 0.00 H lam: H: 5000 0.0 0.0 0.00 0.NN :13 0.0. 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In In In In In nun \mlnn o czononm 0.0 0.0 0.2 0.H: 0.00 m.H H 010 0.0m M 0.00 00 0530 0.0 0.0 0.0 0.0 0.02 0.0 H fim 0.0m H 0.00 0 5000 e 0.0 0.0 0.0 H.0m N00 0.H H 0.0 0.2m H 0.0: 0H fieoz emeHHcmo 0.H 0.H 0.8 0.00 0.H: 0.0 H 0.m 0.00 H m.mm m» 00Ne>< 0.0 0.0 0.00 0.0 0.0: 0.0 H 0.0 0.1:“ 0.:: m 0300320 0.0 0.0 0.0: 0.0m 0.0: m0 H mé N00 H 0.00 2 0530 0.0 0.m m.0H 03,3 0.:: m0 H 0.: 0.00 H 0.Hm 0: 5000 0.0 0.0 0.00 0.00 0.0m m6 H 0.0 m.00 H 0.00 HH 5.82 3038. upcoopwau unamULoal nucwopmau 100002: 1.80: mW%0 ooco 0mm: zuHHmuqu on: to»: com: uoz 6mm acmHoz vaaEmn mend. uoHnooz acmpgso on: msoH>oua ammu~>< ommpo>< pmaEsz mo oocmnW§M. o» mooH .pmnEo>oz Edam mpoHuoo3 cuon pom ALmEEdm mumnommw wwwmh .oH oHan -76- 0Hasmm cH “C0n0pa 002 \m I O C O O C I O 0 ' C wmaohwpw 0 0 H 0 0 00 H 00 H.0 0 H + N m H 00 + 0 00 00 00000 c0oH00s< 0.0 0.0 0.00 0.00 0.0 0.H.“ 0.: 0.00.“ 0.0: 0H 00000>< 0.0 0.0 0.00H 0.0 0.0 0.0.H 0.: 0.0.“ 0.00 H 030030Hm 0.0 0.0 0.00 0.00 0.0 0.H.“ 0.: 0.00.“ 0.00 0 05030 0.0 0.0 0.0 0.00H 0.0 0.0.“ 0.0 0.0.“ 0.0 H 00:00 I l 000m 0.0 0.0 0.00H 0.0 0.0 0.H + 0.0 0.0 + 0.00 N 00002 000HH00 0.0 0.: 0.00 0.0H 0.: 0.H H 0.0 0.00.“ 0.00 mm 00000>< In In In I: In In: \Munu o :30030Hm 0.0 0.0 0.00H 0.0 0.0 0.H.“ 0.0 0.00.“ 0.00 0 00030 0.0 0.0 0.00H 0.0 0.0 0.0 H_0.0 0.0 .H 0.00 H 00:00 0.0 0.0 0.00 m.0m 0.0 0.H H 0.: 0.00 H_0.m0 NH 00002 002000 nud0op0a| 10:000001 :0c0op0au 10000»: n.80: 0m%o 0oco 00m: zuHkupoz 00: c003 0003 02, 0mm 0cmH0: 00H080m 00u¢ uoHnooz 0:00030 005.0500>00a 0mmp0>< 0mmp0>¢ p0nsdz Mo 00:00H>m oomH .0c50 on mooH .u0nE0>oz Scum wuoHvoo3 cgon pom 0005800 0000 co00n :00H00E< .om 0Hamh -77- 0m000>0 0.0 0.0: 0.0: H00 0.00 0.0 H 0.0 0.00 H H.00H 00H 000000 0020 0.0 0.0 0.00 0.0.0 0.00 0.H H 0.: m.0m H 0.00 :0 0000024. 0.0 0.0 0.0 0.0 0.02 0.0 H 0.0 H.m H 0.2 m 0300030 0.0 H.0 0.00 0.00 H.0N 0.H H 0.: 0.00 H 0.00 00 03030 0.0 0.0 0.00 +30 0.00H 0.0 H 0.0 0.NH H 0.H: 0: 580 0.0 0.3 0.00 0.00H 0.3 0.H H 0.: 0.2 H 0.:” 0 50oz 00W0H00H0mo 0.0 0.00 0.H: 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 000003. 0.0 0.00 0.00. 0.00 0.: H.m H 0.: 0.00 H 0.00 :m 0300320 0.0 0.0 m.H0 0.00 0.0. 0.0 H 0.: 0.00 H 0.00 2 05030 0.0 0.0: 0.00H 0.00 0.00 H.0 H 0.0 0.00 u 0.00 00 5000 0.0 0.0 0.0 0.00 0.00. 0.0 H 0.: H.0H .+.. 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Uwom 0.0 0.0 0.00 0.00 0.0 0.0 + 0.0 0.00 + 0.00 00 00002 0000000 0.0 0.0 0.00 0.00 0.0: 0.0 H_m.0 0.00.“ 0.00 00 00000>< In In In In In nun II: o 0300300m .. u- u- -u u- .u. \mun- 0 00030 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00.“ 0.00 0 00000 0.0 0.0 0.00 0.0 0.00 0.0 H 0.0 0.00.“ 0.00 0 00002 000000 300000001 300000001 10000000: 1000021 1.801 0NM0 0000 0000 20000000: 000 000D 000: 002, 000 000000 0000800 000< 0000003 0000000 000 0000>000 0m0002< 0m000>< 000802 1M0 000000>mr @000 .0000 00 m000 000080>02 8000 00000003 0000 000 2008800 0000 00030000 0000008< .mN 00005 -80- 800 20000000 000 800 0000008< 0000 00000000 \0 0.0 0.0.0. 0.00 0.00 0.00 0.0 H 0.m 0.00 H 0.00 80 0000020 000 0.0 0.00 0.00 0.00 0.00 0.0 H 00.0 0.00 H 0.00 000 000.0020 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 03003000 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 00030 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 00000 0.0 0.00 0.00 0.0 0.0 0.0 H 0.m 0.00 H 0.00 00 00002 00mm”? 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 000003. 0.0 0.0 0.000 0.0 0.0 0.0 H 0.0 0.00 H 0.00 0 03003000 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 00030 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 00000 0.0 0.0 0.00 0.00 0.00 0.0 H 0.0 0.00 H 0.00 00 00002 00000.0 n000o000| I000o000| 10000000: :00002I n.801 wUACO ®UCO Ummfl 200000002 000 000: 0003 02» 000 000000 0000800 000<_ 0000003 0000000 000 00o0>00m 0m000>¢ 00000>< 000802 mw100000HWMI \Mo000 .0000 00 mooH 000080302 8000 00000003 0000 000 2008800 0000 80m .0m 00008 Table 25. Common and s ientific names of plants discussed in the text3 Common name American basswood American beech American elm Austrian pine Bitternut hickory Black cherry Black oak Black walnut Chestnut Common elderberry Eastern cottonwood Eastern red cedar Gray birch Hawthorn Ironwood Northern red oak Quaking aspen Red maple Sassafras Scotch pine Serviceberry Shagbark hickory Staghorn sumac Sugar maple Sweet gum Sycamore White ash White oak Yellow birch Yellow poplar %/ From Little, natural zed trees of Handbook—hl,_h72’pp. Scientific name Tilia americana Fagus grandifolia Ulmus americana b Pinus nigra var. austriaca—/ Carya cordiformis Prunus serotina Quercus velutina juglans nigra Castanea dentata Sambucus canadensis Populus deltoides Juniperus Virginiana Betula populifolia Crataegus spp; Ostnya virginiana Quercus rubra Populus tremuloides Acer rubrum Sassafras albidum Pinus sylvestris Amelanchier spp. Carya ovata Rhus Syphfna Acer saccharum fiquidambar straciflua Platanus occidentalis Fraxinus americana Quercus alba Betula alleghaniensis LiriOdendron tulipifera 1953. Check list of native and the United States. «U. 5. Dept. Agr., g/ Wright, J. w., Personal communication, 1900 -82- Table 26. Common and scientific ames of all animals discussed in the texté? Common name Eastern chipmunk Eastern cottontail Elk Florida marsh rabbit Fox squirrel Meadow vole Mountain lion New England cottontail Opossum Racoon Red fox Shorttail shrew Snowshoe hare Southern bog lemming Starnose mole White-footed mouse Whitetail deer Wolf Woodchuck a/ From Hall, Scientific name Tamias striatus Sylvilagus floridanus Cervus canadensis Sylvilagus palustris Sciurus niger Microtus pennsylvanicus Fells concolor Sylvilagus transitionalis Didelphis marsupialis Procyon lotor Vulpes fulva Blarina brevicauda Eepus americanus Synaptomys cooperi Condylura cristata Peromyscus leucopus Dama virginiana Canis lupus Marmota monax and K. R. Kelson, 1959. The mammals of North America, Volumns I and 11, Ronald Press, New York, 1162 pp. VITA John Beatty Mathies Candidate for the Degree of Final Examination: Dissertation: Outline of Studies: Master of Science April 7, 1967 Influence of the Eastern cottontail on tree reproduction in sugar maple-beech stands of southern Michigan Major subject: Forestry Minor subject: Biographical Items: Born: Wildlife Management August 2, 1939, Seattle, Washington Undergraduate Studies: University of Washington, 1958-1962 B. S. 1962 Graduate Studies: Experience: Member: Michigan State University, 1965 to present U. 8. Army Medical Corps, 1957-1958; Forestry Aid, U. S. Forest Service, 1960; Forestry Technician, U. 8. Forest Service, 1961; Forester, U. S. Forest Service, 1962-1965; Graduate Teaching Assistant, Michigan State University, 1965 to present Xi Sigma Pi Society of American Foresters The Canadian Institute of Forestry The Wildlife Society -83- “1i iii 1111111111111 1'“