met or: wmn AND W PmTEcmN 9:: THE ’ EARLY smwm RESPONSE OF 13mm ‘ ’ WALNUT (mm mm M for 3w Dame a: mu. mmm s’rmmvmm. mm. [sauce emuwm ’ 1971 WW! I WNW/WIWWIW LL 3 1293 00809 1393 TM!“ “ This is to certify that the thesis entitled Effect of Wind and Wind Protection on the Early Growth Response of Black Walnut (Jgglans Nigra) presented by Randall Bruce Heiligmann has been accepted towards fulfillment of the requirements for Ph.D. Forestry degree in Major professor Date MaLZO , 197 1 0-169 LIBRA RY Mkhigaa State University it; P 7 ‘_ . ABSTRACT EFFECT OF WIND AND WIND PROTECTION ON THE EARLY GROWTH RESPONSE OF BLACK WALNUT (JUGLANS NIGRA) BY Randall Bruce Heiligmann This study examined the growth response of black walnut to (l) the influence of wind barriers on field planted seedlings, and (2) the effects of a controlled environment where wind velocity approximates that to which field-grown black walnut seedlings are normally exposed. The influence of wind barriers on lB-week-old black walnut seedlings was examined by comparing the growth response and microenvironment of seedlings grow- ing on the leeward side of wooden lath wind barriers with that of seedlings growing in adjacent unprotected areas. Wind, solar radiation, air temperature, relative humidity, soil temperature, and soil moisture were monitored. Seedling stem height and diameter were periodically mea- sured throughout the growing season. The study was con- cluded with determination of total leaf area, oven-dry weight of stem, foliage, and root, and depth of root penetration. Xylem sap tensions were measured with a Randall Bruce Heiligmann pressure bomb to evaluate wind barrier effects on seedling internal water status. Wind barriers significantly affected wind velocity, solar radiation, and air temperature. Compared to the exposed plots, the protected plots had reductions in wind velocities and solar radiation of 67 percent and 18 per- cent, respectively. Maximum and minimum air temperatures averaged 2.9°C and l.6°C higher, reSpectively, in the protected plots. Differences between the exposed and pro- tected plots in the amount of solar radiation received and in air temperature were closely associated with the degree of cloudiness. The wind barriers significantly increased the size of the black walnut seedlings in all growth parameters measured except depth of root penetration. Leaf senes- cence began on seedlings growing in the exposed plots by mid-August while those in the protected plots showed little evidence of senescence by mid-September. No significant difference was found in xylem sap tension of seedlings in the protected and exposed plots. The effects of wind under controlled environmental conditions were studied by examining the growth responses of germinating black walnut seedlings for 80 days under two wind velocities (HumucomonoH mo moflumflnmpomumno HmoHEozo paw Hmoflmwnmll.a mqmde 10 .NH HoQEoumom on H Honsoumom oofluom cofium>uomnoo .mommgucmnmm ca popnooou musumnmmsmu ESEACHE a .momonuconmm :H oopuooou ousumnomfiou EdEflxmzm o.moa m.m «.5 0vom Am.mv v.HH A¢.mmv m.mm Amanav HmnEoumom m.m> m.mH H.m mmv Av.mv o.va Am.HmV m.nm umsmsm m.moa m.nH ~.mH New 1s.mv «.mfi Av.mmv o.k~ mane m.oaa v.ma m.ma wmv Am.mv m.mH Am.amv m.mm ocsn H.Hva m.n m.v In: QAm.HV m.oa mam.mmv o.m~ Aamnmav has .Amhoamcmav hmp\Ex nnnnnnnnnnn Eo nnnnnnnnnnnnn :oHDMHpmm nnnnnnnnn Oo nnnnnnnnnn pcflz coflumuomm>m cofiumuflmfloonm umaom Susana: Esaflxmz nucoz zaflma ousumuomaoa Had ommno>m mHflmo ommuo>d .commom mCH3oum obma 03p mcHHS© Houcoo soumomou own» muflmno>wco oawum cmmfl30flz um mcofiuflpcoo HmoflmoHouoouozlt.m mqmfie 11 thirty-six walnut trees planted in a row on the east side of a north-south oriented wind barrier and a paired ex- posed plot of thirty-six trees planted in a row in an adjacent exposed area (Figure 1). Each L-shaped wind barrier consisted of a twenty- five meter long section oriented north-south and a 2.5 meter section extending eastward from the southern end of the north-south section. Each portion of the wind barrier was composed of three thicknesses of 1.2 meter high wooden lath snowfence. To the west of the north- south axis to a distance of 7.5 meters were six rows of small trees and a second row of three thicknesses of snowfence. gees Black walnut seeds were collected in the Fall of 1969 from two trees in Cass County, Michigan. The seeds were immediately husked, cleaned, placed in string bags, and buried two feet below ground level. On April 27, 1970 the seeds were lifted, placed in wooden flats, and covered with three to four inches of soil. The flats remained out-of—doors and were kept moist until May 15. At that time seeds with radicles beginning to emerge were selected for planting. 12 |’l. II. lion! 1. I .QOflDmoflHmoH paoww oco Amy paw cmwmop poam Adv "mmcflapoom pandas xowan mo SDBOHm so mowuoououm pcfl3 mo muoommo ozp mawcflemxo :mwmop paowmln.a ousmflm 13 < Hofinumflvcwz H mom ood0m3ocm I mmw-H-H IIIIIII a mom m mom l4 Establishment Germinating seeds were planted in three replica- tions on May 16, 1970. The 36 trees behind the wind bar- rier were planted 61 cm apart in a row 61 cm to the east of the barrier. The trees in the exposed plot were planted 61 cm apart in a row directly in line with the trees behind the wind barrier (Figure 1). To facilitate planting and encourage early root development, the plant- ing site was prepared by rototilling along the planting row to a depth of 12.5 cm. The seeds were planted at a depth of 3 to 5 cm, with the radicle tips pointing down- ward. Each seed received four gallons of water after planting. A second watering, equivalent to 2.5 cm of water, was applied to the soil surface by aerial irriga- tion on May 20. A weed-free strip of 30 cm was maintained around each seedling throughout the growing season by hand weed- ing and monthly application of Amitrol-T (31 ml per liter of water). The surrounding area was kept closely mowed to prevent vegetation from interferring with wind move- ment. On June 19 and August 13 the trees were Sprayed with a mixture of 31 m1 of Sevin and 8 m1 of malathion per liter of water to protect them from defoliating insects. 15 Micrometeorological Measurements Wind.--The effect of the wind barriers on wind velocity was determined by calibrating the barriers using pairs of 3-cup anemometers and rate meters. Anemometers were placed at 6.2, 12.5, and 18.8 meters from the end of each wind barrier while others were placed in compar- -able positions in the adjacent exposed plots. The anemometers were placed within the plant rows at a mid- cup height of 30 cm. Wind velocities were recorded simultaneously on the exposed plot and behind the bar- rier. Fifty readings were taken at each location at 30-second intervals at different periods of time through- out the summer. Solar radiation.--Solar radiation was monitored with two pyrheliographs located in Replicate 2. One pyrheliograph sensor, at a height of 20 cm, was located 6.2 meters from the northern end of the wind barrier and the other in a comparable position in the adjacent ex- posed plot. Air temperature--relative humidity.--Daily maximum—minimum temperatures were obtained from shielded mercury-in-glass maximum-minimum thermometers placed 18 cm above the soil surface at the center of each plot. A recording of daily temperatures and relative humidity 16 was also obtained on the exposed plot and behind the barrier from two hygrothermographs located in Replicate l and positioned within the rows in the same manner as the pyrheliographs in Replicate 2. Soil temperature-—soil moisture.--Daily tempera- tures and weekly moisture measurements were made for the upper 15 cm of soil between 8 and 10 a.m. Soil tempera- ture was obtained from shielded mercury-in—glass thermo- meters inserted in the soil at the center of each plot. Soil moisture measurements were gravimetrically determined by obtaining a core sample from a randomly selected loca- tion in each plot. Plant Measurements Mylem sap tension.--Trees were randomly selected from each plot between 6:00 a.m. and 8:00 p.m. for xylem sap tension determinations with a pressure bomb on September 2, 9, 10, and 11 (Figure 2) (Scholander, §t_§l,, 1965; Waring and Cleary, 1967). Depending upon the magni- tude of the xylem tensions, from 30 to 90 minutes were required to measure such internal water stresses for all replications. Each tree was sampled by selecting a healthy com- pound leaf in the upper third of the crown and removing the distal 3 leaflets by cutting the rachis immediately 17 Figure 2.--Pressure bomb used to determine xylem sap ten- sions of black walnut seedlings. 18 19 above the fourth and fifth leaflets with a sharp razor blade. This portion of the leaf was placed in the pres- sure bomb with the rachis extending through the compres- sion membrane and out the top of the bomb approximately 3 mm. The gas pressure in the bomb was then gradually increased 5 psi every 10 seconds until xylem sap first appeared at the cut surface of the rachis. The best estimate of xylem sap tension was interpreted as the pressure in the chamber when xylem sap first appeared at the cut surface of the rachis minus 2.5 psi. When each tree was sampled for xylem sap tension, concurrent observations were made of air temperature, wind velocity, and relative humidity. Soil moisture content was determined on September 2 and September 10 and total daily solar radiation was determined for all four days. Plant growth.--The total height and stem diameter at 2.5 cm above the ground were determined for all trees every 2 to 3 weeks during the study. Height was measured to the nearest millimeter with a metric ruler and diameter to the nearest 0.25 mm using a micrometer. At the termination of the study, September 15 to 22, the following measurements were taken: On all trees 1. Total height above ground (cm) 2. Total height above root collar (cm) 20 3. Diameter 2.5 cm above ground (cm) 4. Oven-dry weight of stem (9) 5. Oven-dry weight of foliage (9) On a subsample of 9 trees randomly selected from each plot 1. Length and width of each leaflet on the tree (cm) 2. Depth of root penetration (cm) 3. Oven-dry weight of root (9) Oven-dry weights were determined after plant material had been dried to a constant weight of 70°C. Foliar nutrient analyses of the seedlings in the protected and exposed plots were obtained at this time (Table 15). The total leaf area of each of the 54 trees in the subsample was determined by solving the following regression equation (R2 = .99) for each leaflet and sum- ming the values obtained for all the leaflets on the tree: Leaflet Area = .105 + .663 [leaflet length (cm)] [leaflet width (cm)] Information on the root systems of the trees in the subsample was obtained byexcavating the root sys- tems. This was accomplished by first digging a trench 2 meters deep and 1 meter to the side of each row of trees and then removing the root systems by washing away the soil with water under pressure (Figure 3). 21 .mmnam H0063 £0w3 HHom may Eoum mEoummm poou mo Hm>oEoH Amy pcm mcflnocouu Amy mafi3ogm :0flpm>moxo poomla.m onsmflm 22 23 Results and Discussion of Micro- meteorological Factors m The average velocity of prevailing winds at mid- crown height (25-30 cm) in the protected plots was 33 per- cent of that in the exposed plots (Table 3). Approximately 75 percent of this reduction in wind velocity by the bar- riers was attributable to the 3 layers of snowfence, 61 cm to the west of the plant row (Khattak, 1968). Variations in the effectiveness of the barriers in reducing wind velocity were undoubtedly due to varia- tions in the permeability* of the wind barrier. Some additional variation may have been introduced during calibration because of differences in the velocities of winds blowing against the barriers and in the exposed plots. Wind reduction by the barrier appeared to apply uniformly to all winds less than 16 km/hour, the maximum wind velocity observed during the calibration period. Similar observations have been reported for wooden lath wind barriers by Gloyne (1965) and for moderately im- permeable natural windbreaks by Read (1964). *Permeability is the ratio of air space in a barrier to its total surface area (Hogg, 1965a). 24 TABLE 3.--Wind barrier effectiveness in reducing wind velocity. Barrier Relative Wind (%)* Rep 1 31.5 Rep 2 27.5 Rep 3 38.9 Wind at sheltered Site x 100 (Hogg, 1965a) * ' ' = Relative Wlnd Unobstructed wind 600‘ >. soo~ ‘U Q U) 400d 0......0......OIIIIII° >1 DD... 0‘ 9. Q. 0. ‘0'. 3 .0. 0.. O. 0‘ “‘ 300— .0 9°. ”0““ 23 d’ (U Q 2001 Exposed Plot 100... .IIIIIIII Protected Plot 1 I I 1 T T’ I l ' l ' ‘ I 6/7 6/14 5/21 6/28 7/5 7/12 7/19 7/26 8/2 8/9 8/16 8/23 8fl0 Week Beginning Figure 4.--Week1y averages of daily solar radiation in exposed and protected plots. & 25 Solar Radiation The average daily solar radiation received by the trees growing behind the wind barrier was 82 percent of that received by the trees growing in the exposed plot (Figure 4). Observations in a comparable position behind north-south shelterbelts near Vienna by Dirmhirn (1953) indicated reduced insolation of 72 to 84 percent. Reduc- tion in solar radiation by the barrier on a given day, however, varied between 0 and 30 percent and appears re- lated to conditions of cloud cover. The reduction in the amount of solar radiation received by the trees behind the barrier was greatest on clear days when direct radiation was the larger propor— tion of total solar radiation. By shading the protected plot, the barrier intercepted much of the direct solar radiation when the sun was in the western sky. This is well illustrated in the pyrheliographs recorded on August 2 (Figure 5). The trees growing in the protected plot received approximately 473 langleys of solar radiation while those growing in the exposed plot received 591 langleys. The abrupt drop in solar radiation behind the barrier occurred between 2:00 and 3:00 p.m. On overcast days, however, direct radiation makes up a smaller proportion of the total solar radiation than it does on clear days. On overcast days barrier inter- ception of radiation from the western aspect was less _1__ Exposed Plot ‘"-' Protected Plot Solar Radiation (Langleys/Day) Time 5.--Solar radiation received in exposed and pro- tected plots on August 2, a clear day. ’11 p. LQ C.’ H (D - Exposed Plot ---- Protected Plot Solar Radiation (Langleys/Day) Time Figure 6.--Solar radiation received in exposed and pro- tected plots on July 23, an overcast day. 27 effective in reducing the total solar radiation received by the trees in the protected plot than on clear days. Although diffuse radiation from the western direction was blocked by the barrier, this was apparently compensated for by diffuse radiation from the eastern sky striking the barrier and its subsequent reflection to the plot. This type of day was recorded by the pyrheliograph on July 23 (Figure 6). Both exposed and protected plots received approximately 276 langleys of solar radiation. Consequently on any particular day the percent of the total solar radiation received by the plants be- hind the wind barrier appears dependent on the amount of cloud cover during the afternoon of that day. The more clear the afternoon sky, the less the percentage of total solar radiation received by the trees behind the bar- riers. Similar observations have been made by Geiger (1966) in considering the local climate at the different edges of a forest stand. He notes that "the greater the proportion of diffuse radiation to direct sunshine, . . . as in cloudy weather . . . the less will be the differ- ence between different edges." Air Temperature Typical temperature patterns for days of high and low solar radiation are shown in Figures 7 and 8. Two differences are apparent. First, air temperatures on cloudless days are considerably higher behind the barrier 28 35 .— EXPOSGd P10t ---- Protected Plot Air Temperature (°C) I I I I I -l I I I 1 Time Figure 7.--Air temperature in exposed and protected plots on August 2, a clear day. 35 - ———— Exposed Plot ---- Protected Plot 30-1 25J Air Temperature (°C) Time Figure 8.--Air temperature in exposed and protected plots on July 23, an overcast day. 29 than those in the exposed plots during the morning and early afternoon hours. This also occurs on overcast days but to a much lesser extent. An explanation is that in the morning solar radiation heats the soil surface to a temperature greater than that of the air. By conduc- tion, the air layer overlying the soil surface is heated. On exposed plots the wind and convection currents rapidly mix this heated air with the air above it, reducing the development of a stagnant layer of warm air near the ground. Behind the wind barrier, where wind turbulence is greatly reduced, mixing occurs more slowly and a layer of warm air near the ground surface develops. Stoeckeler (1962) reported that increases in midday air temperatures to the leeward side of dense shelterbelts resulted from ". . . air stagnation and hence more heating out to about 3 H." (H = times height of shelterbelt.) This effect would be intensified on sunny days because the increased input of solar radiation produces higher soil surface temperatures and a greater heating of the overlying layer of air. The second difference observed was that the air temperatures on sunny days were higher on the exposed plots than those behind the barriers during the middle and late afternoon hours but on overcast afternoons there was little temperature difference between the exposed and protected plots. Recalling the effect of the barrier 30 on solar radiation, the plots behind the barriers were shielded from much of the direct solar radiation during the middle and late afternoon on sunny days. This reduc- tion in solar radiation would have two results: (1) a reduction in the radiant heating of the air in the shaded area and (2) a reduction in the radiant heating of the soil surface in the shaded area. The cooler soil and reduced wind velocities behind the barrier would result in a cooler layer of air overlying the ground surface behind the barrier than in the exposed plot. On over- cast days, when the solar radiation received in the exposed and protected plots was nearly the same, there would be little difference in the radiant heating of the air and soil between the plots. Maximum air temperatures in the protected plots were found to be significantly (5%) greater than those in the exposed plots. Throughout the summer, maximum air temperatures behind the barriers averaged 2.9°C higher than in the adjacent exposed plots (Figure 9). This difference was primarily the result of the increase in air temperature which occurred during the morning and early afternoons in the protected plots. The final effect of the wind barriers on the air temperature in the protected plots was to significantly increase the minimum air temperatures. The minimum air temperatures in the protected plots averaged l.6°C .51 Air Temperature (%) N c: l -— Exposed Plot ununm Protected Plot 'I I I n I I I I I I I m 6/7 6/14 6/216/287/5 7/127/19 7/26 8/2 8/9 8/16 8/23 Week Beginning Figure 9.-—Week1y average maximum and minimum air temper- atures in exposed and protected plots. 60 ‘ 2»? >150 ‘ .p -:-l o E a: 40 - o > H 4.3 m Fl 32 30 -I —— Exposed Plot s m..." Protected Plot I I I I I I I I I I I I I 6/7 6/14 6/21 6/28 7/5 7/12 7/19 7fl6 8/2 8/9 8/16 8/23 8/30 Week Beginning Figure 10.—-Week1y average relative humidities in exposed and protected plots. 32 higher than those in the exposed plots (Figure 9). It should be noted that all minimum air temperatures occurred during the night, usually just prior to sunrise. At night the net long-wavelength radiation from the soil surface is usually outward resulting in the cooling of the ground surface. Lausher (1934) reported that the net long-wavelength radiation in the vicinity of a barrier was less than for a relatively flat ground surface. There- fore, a slower rate of cooling of the ground surface in the vicinity of the barrier results in a warmer soil sur- face behind the barrier at any given time during the night. The warmer soil surface behind the barrier and a reduced wind velocity would result in a higher minimum air temperature behind the barrier than in the exposed plot. Relative Humidity Daily maximum and minimum relative humidities on the protected plot were not significantly different from those recorded on the exposed plot. On both plots the maximum relative humidity reached 100 percent on 92 per- cent of the nights. On no night was the maximum relative humidity less than 85 percent. Weekly average minimum relative humidities for the protected and exposed plots are presented in Figure 10. 33 Soil Temperature There was no significant difference between the temperatures of the upper 15 cm of soil recorded daily at 8:00 a.m. in the exposed and protected plots (Figure 11). On any particular day, differences between soil tempera- ture in the exposed and protected plots of the same replication were seldom greater than 0.5°C. Soil Moisture There was no significant difference between the soil moisture content (percent by weight) of the upper 15 cm of soil in the protected plot and in the exposed plot (Figure 12). Working with similar wind barriers, Khattak (1968) reported the same results for the upper 30 cm of soil at a distance equal to the height of the barriers (1.2 meters) to the leeward side of the barriers. Results and Discussion of Plant Measurements Plant Growth Shoot development.--The effects of wind barriers on the shoot growth of lB-week-old black walnut seedlings are presented in Table 4 and Figure 13. Stem height was increased by 15 percent, stem diameter by 13.5 percent, and stem oven-dry weight by 46 percent. The total leaf area per seedling and the total oven-dry weight of the foliage were increased by 85 percent and 158 percent respectively. This resulted from the trees on the 30- lO-‘ Soil Temperature (°C) 34 .__— Exposed Plot "sou. Protected PlOt I I I I *T l‘ I I I I 6/7 6/14 6/21 6/28 7/5 7rfl.2 7}].9 7R6 8/2 8/9 8/16 8/23 Week Beginning Figure ll.--Weekly average temperature of upper 15 cm of soil in exposed and protected plots. 20'- 13 .c m -H o 3 1£5- >., .Q 0\0 8 lO- 5 4.: U) -a o z 5 a 55 -— Exposed Plot m '""" Protected Plot I I I I I I I I 1 I 1 6/7 6/17 6/27 7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 Date Figure 12.--Weekly average moisture content (% by weight) of the upper 15 cm of soil in exposed and protected plots. 35 TABLE 4.-_Growth responses of 18-week-old black walnut seed- in exposed and protected field plots. Exposed Protected Level Growth Parameter Plots Plots Significantly Different (%) Stem Height (cha 21.6 24.7 2.1 Stem Diameter (cm) 0.66 0.75 9.2 Stem O.D. Weight (g)> 3.7 5.4 4.7 Total Leaf Area (cmz) 971. 1816. 4.5 Average Number Leaflets 63. 92. 8.7 Average Leaflet Length (cm) 6.4 7.2 4.0 Average Leaflet Width (cm) 3.3 3.6 2.9 Leaves O.D. Weight (g) 5.0 12.9 0.1 Shoot O.D. Weight (g) 8.7 18.3 0.2 Depth Root Penetration (cm)b 53.7 54.9 86.4 Root 0.0. Weight (g)b 28.5 36.3 6.7 Root/Shoot (length)b 2.5 2.3 38.8 Root/Shoot (weight)b 2.7 2.1 4.8 a Measured from root collar. bDetermined from subsample. 36 .pon pomomxo Amy was uoam oouoououm Adv ca DSCHMS Roman GHOIMooBImH mo pcoemoHo>op uoongI.ma ousmflm 37 U ... 3 fl... ’. t V a... 38 protected plots having (1) 46 percent more leaflets than those on the exposed plots and (2) leaflets 12 percent longer and 9 percent wider than those on the trees in the exposed plots. Similar effects of wind barriers on the stem diameter, stem height, and total leaf area of black walnut seedlings have been reported by Khattak (1968), though he did not observe significant differences until the middle of the second year after planting. However, Khattak planted 1/0 seedlings, the shoot growth of which would not be expected to respond to cultural treatments as rapidly during their first year after planting as trees planted from seed. The difference in the stem height growth between the exposed and protected plots appears to have develoPed in two ways. Prior to August 3, the terminal growth rate in the protected plots was greater, though not signifi- cantly, than that in the exposed plots (Table 5). During this time the wind barriers appear to have been providing a more favorable environment for terminal growth than that which existed in the exposed plots. After August 3, the terminal growth in the exposed plots virtually ceased while that in the protected plots continued at a signifi- cantly greater rate. The wind barriers appear to have extended the period of terminal growth by several weeks. The presence of wind barriers had little observ- able effect on stem diameter growth prior to August 3 39 v.5 v.o o.o m.m m.H~ a.ma ma .uamm o.¢ m.o H.o m.m v.Hm a.ma mm .msm m.~w v.H m.H m.vH o.o~ a.ma m .m5< S.Hm ~.~ m.H a.ma H.aa k.sa ma sass o.Hm o.m m.m N.¢~ a.ma a.ma em mash N.mH a.ma o.ma N.ma m.ma a.ma m mash IIIII wIIII IIIIIIIIIIIEUIIIIIIII IIIIIwIIII IIIIIIIIIIEUIIIIIIII uGoHQOMHQ muon muoam ucouommao mpon muon mama .cmwmIHm>oA mouoououm .womomxm .cmwm Ho>oq wouoopoum monomxm mcflHmEmm ucoEouocH QDBOHO nusouw Hmuoe .muoaa cameo pouoogoum was pomomxo ca mmcfiapoom pandas Roman mo rusoum named: 0fipofinomII.m mqmda 40 (Table 6). The environmental modification by the barrier which appeared to favor increased stem height growth apparently did not affect stem diameter growth. After August 3, stem diameter growth in the protected plots was significantly greater than that in the exposed plots. In addition to affecting the number and size of the leaflets of the seedlings, the wind barrier apparently affected the time of the onset of leaf senescence. By the latter part of August the discoloration that is typi- cal of the senescing leaves of black walnut was evident in the seedlings in the exposed plots. Seedlings in the protected plots showed little evidence of senescence by mid-September. This early senescence of the leaves in the exposed plots may be related to the decline in growth rates observed in the exposed plots. Recent work by Carpenter (1971) indicates that toward the end of the growing season, when leaf senescence and abscision are occurring, rates of net photosynthesis are lower than earlier in the growing season. Root development and root/shoot ratio.--The presence of the wind barriers significantly increased the root ovenédry weight by 27 percent and decreased the root/shoot weight ratio by 22 percent. The depth of root penetration and the root/shoot length ratio were not influenced by the wind barrier (Table 4, Figure 14). The 41 N.m mo. mo. N.m mm. mm. ma .umom n.o NH. mo. >.oa on. we. om .msm m.bm mo. ca. a.mm mm. mm. m .msd m.~m mo. mo. a.mH cm. as. NH sass H.om mo. mo. m.Hm ov. av. vm mean H.ov Hm. mm. H.ov Hm. mm. m ocso IIIII wIIII IIIIIIIIIIIEUIIIIIIII IIIIIwIIII IIIIIIIIIIIEOIIIIIIII ucoquMHo muon muon uconomman muon muoam oumo .cmwm Ho>oq pouoouonm pomomxm .cmwm Ho>oq pouoopoum pomomxm mcHHmEmm ucoaouocH nu3ouw , nuzouu Hmuoe .muoHE camau wouoououm paw pomomxo :H mmcflapoom uncam3 Rowan mo nusoum noboemflp napoflnomII.o mqmde 42 A.©wum 80 m "manomv .DOHQ boycoDOHm Amy can uon pomom Ixo Amy cw pscHMB Roman pHOIxooBImH mo acoEmoHo>o© uoou paw EoumII.vH onsmwm 43 ‘N 44 lower root/shoot weight ratio of the seedlings in the pro- tected plots resulted from the wind barriers causing greater increases in shoot weight (110 percent) than in root weight (27 percent). This difference in growth be- tween the shoots and roots may have resulted from (1) the redistribution in the protected plots of the total seed- ling productivity in favor of the shoots throughout the growing period or (2) the decline in seedling shoot growth in the exposed plots earlier than in the protected plots while the roots of the seedlings in both plots con- tinued to grow. Root penetration was highly variable on both the protected and exposed plots with depths of penetration ranging between 25 cm and 102 cm on the protected plots and between 22 cm and 97 cm on the exposed plots. A large portion of this variation may have resulted from the variation in the soil structure and horizon thickness which existed throughout the study area. Xylem Sap Tension The xylem sap tensions of the black walnut seed- lings in the protected and exposed plots were examined to determine if the presence of the wind barriers affected the internal water status of the trees. Difference in the internal water status of the seedlings, if of sufficient magnitude, could result in observable differences in 45 seedling growth byIaffecting stomatal aperture and/or plant processes involved in growth. The daily pattern for xylem sap tension in the seedlings in the exposed and protected plots for September 2 is presented in Table 7. The daily patterns in xylem tension for September 9, 10, and 11 were quite similar. Following sunrise the xylem tension rose rapidly until around midday when the rate of change in the tensions became relatively slow. This plateau was maintained until around 4:00 p.m., at which time the tensions began to decrease. Similar patterns in the daily course of rela- tive water content in millet (Begg, g£_al., 1964), xylem sap tension in black walnut (Khattak, 1968), relative turgidity in cotton (Weatherly, 1950), and moisture con- tent of sunflower and amaranthus (Wilson, gt_al., 1953) have been reported. Because of the rapid changes in xylem tensions during the morning and late afternoon, only tension mea- surements taken during the "plateau period" were con- sidered comparable. The average xylem sap tensions dur- ing the "plateau periods" of September 2, 9, 10, and 11 along with the concurrent environmental conditions are presented in Table 8. On these four days there were no significant differences between the xylem tensions of the seedlings in the exposed and protected plots during the "plateau periods." This result agrees with previous 46 TABLE 7.--Daily pattern of xylem sap tension of first-year black walnut seedlings in exposed and protected plots on September 2, 1970. Rep 'Protected Plot ' - Expgsed Plot Time Tension (atm) Time Tension (atm) 1 6:32 a.m. .2 6:40 a.m. .5 2 6:47 a.m. .5 6:55 a.m. .9 3 7:04 a.m 1.2 7:10 a.m. 2.2 1 9:43 a.m. 10.1 10:00 a.m. 11.9 2 10:25 a.m. 11.2 10:24 a.m. 13.6 3 11:15 a.m. 12.6 11:36 a.m. 12.8 1 1:15 p.m. 13.6 1:40 p.m. 16.0 2 2:45 p.m. 14.3 2:30 p.m. 14.0 3 3:20 p.m. 15.0 3:43 p.m. 16.0 1 5:36 p.m. 11.9 ' 5:55 p.m. 13.3 2 6:53 p.m. 4.0 7:09 p.m. 5.3 47 n.va v.va Ham vmm ovIom m.mNIv.vm III III m m.ma a.ma HH\m mam omIov m.mmIo.om m.n m.m ma m.va o.va oa\m now omIov m.mmIm.mm III III m m.ma m.mH m\m mom omIov o.OMIm.nN m.n a.m m v.ma v.va m\m Ammoamcmav Aum\fixv COABMHpmm Amy Auov Eo QMImH EU mHIo ucoEoHSm awaom mpflpHEsm .mEoB was A.u3 wv Imoz mcfluso pmmomxm oouoououm oumo mHHmo o>flumHom onsumfloz Hflom .m>4 muflooHo> AEumv coflmcoe uon .m>« Hmuoe pcflz .xmz .onma .HH paw .0H .m .m quEoumom so .E.m oouv paw cooc oouma comzuon muoHQ pomomxo paw popoonoum co mmCHHUoom usch3 roman mo coflmcou mmm anmx mmmuo>¢II.m mqmde 48 measurements made in the month of July on black walnut growing behind similar barriers (Khattak, 1968). Several explanations that could be offered for the effect of the wind barriers on the xylem sap tension of black walnut seedlings observed are: l. The presence of wind barriers does not affect xylem sap tensions of seedlings planted to their lee at any time. 2. During the period of maximum xylem tension, the "plateau period," the barriers do not affect the xylem sap tension but during per- iods of less tension the barriers do have an effect on tension. 3. Only under certain environmental conditions, different from those of September 2, 9, 10, and 11, do the barriers affect the xylem sap tension. 4. The barriers affect the xylem sap tension during part of the growing season but not during the period when the measurements were taken. Additional study would be needed to determine if any of these hypotheses are correct._ Furthermore, the technique used to determine xylem sap tension in this study was not entirely satisfactory. It is suggested that in any future work more than one pressure bomb be 49 used and simultaneous readings be made in all treatment combinations. Measurements taken at any time during the day would thus be comparable. In addition, the variation in tension due to the time of day of sampling could be removed from the analysis by the proper statistical technique. This would allow measurements to be taken over an entire day or several days and then analyzed together. Some of the extraneous variation in the xylem sap tension could be further reduced by better control of the soil moisture in the vicinity of the trees. A more accurate evaluation of the effects of imposed treat- ments on the xylem sap tension could be obtained by grow- ing the trees in containers in which soil moisture is controlled. CHAPTER III CONTROLLED ENVIRONMENTAL STUDY OF THE EFFECTS OF A MODERATE WIND VELOCITY ON FIRST-YEAR BLACK WALNUT SEEDLINGS Introduction It is difficult to modify wind in field studies without altering other environmental factors. There is also the potential risk of introducing unknown inter- actions between wind and other environmental factors. Therefore, the effects of wind on plants can best be studied under controlled environmental conditions. In comparison with other environmental factors, relatively few such controlled environmental studies have examined the effects of wind on plant growth. Hill (1921) reported that a 5 m/sec wind for 24 hours a day reduced the germination and growth of cress and mustard growing on lamp-wicks. Finnel (1928) observed that marigolds exposed to a 15 m.p.h. wind for 60 days were shorter, less mature, had less total dry weight, and had more deformed or des- troyed foliage than control plants. Martin and Clements (1935) reported that exposure of sunflower (Helianthus annuus) to increasingly higher 50 51 wind velocities of 0, 5, 10, and 15 m.p.h. for a period of 6 to 8 weeks caused progressively less growth in leaf area, stem height and diameter, and dry weight. Rao (1938) reported that Italian millet (Setaria italica) plants grown in an 11 m.p.h. wind for one month were shorter and had thinner stems, narrower and shorter leaves, less shoot and root dry weight, and less root volume than the control plants. Wadsworth (1959), working with rape (Brassica napug), observed that as these plants were subjected to progressively higher wind velocities their growth rates first increased and then decreased. He suggested that there is an Optimum wind speed, which he estimated to be approximately 0.3 m/sec for rape under his experimental conditions, above and below which growth rate will be less than maximum. Whitehead (1957, 1962, 1963) and Whitehead and Luti (1962) studied the effects of wind on the growth of corn (£23 Mays) and sunflower (H. annuus).) Exposing corn plants to a 30 m.p.h. wind caused a decrease in height, weight of roots and shoots, and leaf length, and an in- crease in the leaf width and thickness, the root/shoot weight ratio, and the root length. With increasing wind velocities of l, 9, l9, and 33 m.p.h. sunflower plants exhibited progressive decreases in leaf area, height 52 growth, root and shoot dry weight, and a progressive in- crease in the root/shoot weight ratio. Satoo (1962) reported that exposure of black locust (Robina pseudoacacia) seedlings to a 3.6 m/sec wind for 4 weeks caused a decrease in stem height and diameter, shoot and root dry weight, number and length of leaflets, and length of root. This portion of the study was designed to evalu- ate, under controlled environmental conditions, the effects on black walnut seedlings of a wind equal in velocity to the average wind at the field study site. Of primary interest was the growth response of the seed— lings. In order to gain some insight into the physio- logical response of the seedlings, information was also obtained on the transpiration and stomatal re5ponses to the wind and to the soil moisture levels maintained. Methods The growth responses of germinating black walnut seedlings were studied for 80 days under two different wind velocities and two different soil moisture regimes. The study was carried out in two wind tunnels located in an environment room which provided control of both ambient air temperature and relative humidity (Figure 15). Wind velocities were maintained at either 2.8 m/sec or <0.l m/sec for 11 hours a day, beginning one 53 Figure 15.--View of tunnels used to examine the effects of wind on black walnut seedlings: (A) low wind velocity tunnel and (B and C) side and end of high wind velocity tunnel. 54 55 hour after the lights came on and ending two hours before the lights went off. The lower velocity, or control, was maintained to prevent air stagnation in the tunnel. Within each wind tunnel the seedlings were randomly assigned to one of two soil moisture regimes. Soil moisture was either allowed to fall to 8 per- cent* and then rewatered to 12 percent (the high soil moisture regime), or allowed to fall to 4 percent and then rewatered to 12 percent (the low soil moisture regime). These soil moisture levels, 12 percent, 8 percent, and 4 percent, correspond to soil water suctions of 0.20 atm., 0.75 atm., and 7.00 atm. respectively (Figure 16). The seedlings received a 14 hour photoperiod pro- vided by a bank of 6 Sylvania 40-watt cool-white fluores- cent and 8 25-watt incandescent light bulbs. The average illumination in the seedling crowns was 1200 foot-candles. Air temperature was maintained at 20°C : 1.5°C at all times. Leaf temperatures, recorded with an infrared thermometer, were less than 1°C above ambient air temper- ature and varied by less than 1°C between the two tun- nels. Soil temperature varied between a high of 21.6°C during the day and a low of l9.4°C at night. Both day and night relative humidity was maintained at 60 to 65 percent. The carbon dioxide level in the air of the *All soil moisture percentages are expressed on a weight basis. 56 m .coflmcou Eum HIo maflmuoo Magma“ nodmsv unomcH .Hflom EmoH hogan mono: mo mconHon H 4 can m wo moamamm muamomeoo How o>uso oaumHHoDUMHmno ouspmHOE HHomII.oH ousmwm A. fimv COflmCOB «a NH 0H m w v N o p b L .lp — r - r _L _ p — _ n I . . T q lql - + W m I S A.Epmv cowmcme m. 3 m. a. s. m. o I . L _ _ 1 _ _ _ . . _ I W m a m m I. I OH I m w I a O ) 1. l a. + TOHm I .A a a a [man rm. q I q ImHA I n ma T T. L. 5 I w. I ONI Iom 57 tunnels, measured with an infrared gas analyzer, was approximately 300 ppm. The experimental design was a split-plot fac- torial with two replications. Wind was analyzed as a whole plot treatment and soil moisture as a subplot treatment. Each replication consisted of 10 seedlings in each wind tunnel, half of which were randomly assigned to one soil moisture regime and half to the other. Efforts to obtain sufficient seed of both uniform size and time of germination proved unsuccessful. It was, however, possible to obtain groups of 4 germinating seedlings which met these requirements. These were placed, one seedling per treatment combination, into the tunnels at one to three day intervals. This fact was taken into account by introducing into the analysis of variance a main effect, designated as TIME, which re- moved any variation in seedling response, caused by time, between the five four-tree groups. TIME was analyzed as a whole plot treatment which had the desirable effect of increasing the error degrees of freedom for testing the main effect of wind. The black walnut seeds used in this part of the study were collected in the Fall of 1969 from a single tree in Cass County, Michigan. Seed treatment prior to the time of germination was identical to that of the field experiment described in Chapter II. When 58 germination began, approximately 600 seeds were placed in wooden flats, covered with moist soil, and put into a cold room at 4°C for 3 months for later use in the second replication. As germination proceeded, groups of 4 seed- lings of comparable size and weight were selected and each seedling was planted in a 4-liter plastic container filled level with soil (approximately 5625 g of oven-dry soil). The soil used was collected from the Ap and A21 horizons in the field study area described in Chapter II and passed through a 0.64 cm mesh sieve. The containers were watered to 12 percent soil moisture content, placed in the dark- ened controlled environment room for 12 hours, and then positioned in the wind tunnels at the beginning of the day cycle. To insure uniform wind exposure, the seedlings were rotated every other day during the first 60 days in the tunnel. Watering of the seedlings was controlled by con- tainer weight. When the container weight, adjusted for seedling weight*, indicated a soil at either 8 percent or 4 percent moisture content, enough distilled water was added to the container to bring the soil moisture con- tent up to 12 percent. Water was added with the aid of a hypodermic syringe. The needle was inserted into the *Seedling weight was estimated by the following equation (R2 = .74): Seedling Weight (g) = -ll.44 + 132.59 (Stem Diameter in cm at 1 cm height). 59 top and sides of each container and the water was intro- duced at various depths in the soil (Figure 17). To ascertain how effective this technique was in obtaining uniform soil water distribution, 9 walnut seedlings were grown for 5 and 10 weeks using this water- ing technique. Water distribution in the soil was then examined at different soil moisture contents (Table 9). Shortly after watering the distribution of water in the container is fairly uniform. However, as the time since watering increases, the distrubution of water in the con- tainers becomes less uniform, decreasing at the top more rapidly than at the bottom. This differential drying probably results from evaporation from the soil surface and from the absorption of water by the root. It should be noted that the seedling root systems did not fully occupy the soil mass. A total of 450 g of RX-15* nutrient solution was applied to each seedling during its first week in the wind tunnel. This solution was applied in place of dis- tilled water to replenish the soil moisture content. At two week intervals the seedlings were sprayed with a 0.5 percent aqueous solution of zineb to minimize damage by walnut anthracnose, Gnomonia leptostyla (Jaynes, 1969). *Manufactured by Garden Research Laboratories, Ltd., Toronto, Ontario, Canada. 60 Figure l7.--Watering with hypodermic syringe to obtain uniform soil moisture distribution. 61 62 TABLE 9.--Soil water distribution in containers at different soil moisture contents for 5 and lO—week—old black walnut seedlings. Percent Moisture Position of Sample in Container by Container Weight Upper 1/3 Midgle 173 Lower 173 5 Weeks 11.0 11.5 10.4 13.4 11.0 11.6 11.6 11.0 11.0 9.8 9.9 12.8 5.2 3.8 4.6 5.3 5.5 4.5 5.1 5.8 5.3 4.1 4.8 5.6 4.6 2.8 4.6 5.5 5.0 3.8 5.8 6.3 5.0 3.2 5.0 5.8 10 Weeks 9.6 9.5 9.8 10.1 10.3 10.2 10.2 10.0 9.6 9.1 9.4 10.0 7.0 6.3 6.9 6.8 7.0 6.6 6.4 6.8 6.8 6.7 7.3 6.6 3.7 2.0 4.0 4.8 3.6 2.0 4.4 5.0 3.7 2.9 4.6 5.1 63 Both stem height and stem diameter, at 1 cm above the soil surface, were measured every 8 days. Height was measured to the nearest millimeter and diameter to the nearest 0.25 mm. The total leaf area of each seedling was determined every 8 days for the first 48 days and at the end of the study by measuring the length and width of each leaflet on the seedling and applying the pro- cedure described in Chapter II. At the end of the study, the oven-dry weights (70°C) of the leaves, stem, and root of each seedling were determined. At this time foliar nutrient analyses of the seedlings in each treatment combination were obtained (Table 16). Transpiration rates were calculated for each seedling during the last 20-day period in the wind tunnel. The night before the transpiration measurements were be- gun the soil moisture in the containers was brought up to 12 percent and the containers sealed in polyethelene bags to prevent the evaporation of water from the soil. The following morning the containers were weighed and placed in the tunnels for the 11 hour period. At the end of this time the containers were again weighed. The difference in the container's weight before and after the period in the wind tunnel was interpreted as the weight of the water transpired by that seedling during that 11 hour period. 64 Following these transpiration measurements, the polyethelene bags were removed and the trees returned to the wind tunnels. The soil moisture content in all of the containers was allowed to deplete over the next several days until it reached 8 percent, at which time the trans- piration measurements were repeated. The soil moisture content in the containers of the seedlings subjected to the low soil moisture regime was allowed to further de- plate to 4 percent and the transpiration measurements were once again repeated. The leaf areas used to calculate transpiration rate were the leaf areas of the seedlings at the end of the study adjusted for the areas of the leaflets lost between the transpiration measurements and the final leaf measurements. Along with the transpiration measurements, silicon rubber impressions of the lower surface of one leaflet per seedling were taken to evaluate the response of stomata to wind and soil moisture levels. The impressions were taken in the tunnel during the 15 minute period before the wind ended and the final weighing occurred. The techniques of making the impressions and the transparent cellulose acetate positive replicas are described by Sampson (1961) and Zelitch (1961). General Electric RTV-ll liquid silicone rubber and Tenneco Nuocure 28 (2 drops per gram of silicone rubber) were used to make the 65 impressions and a 1:1 solution of clear fingernail polish and acetone to make the positive replicas. To examine the stomatal apertures, the positive replicas were temporarily mounted on glass slides and examined with a compound light-microscope. Stomatal apertures were evaluated on a numerical scale from 1 to 4, with 1 indicating that the stomata were closed (Figure 18). A total of 25 stomata were examined on each leaflet along a line at right angles to the midrib through the center of the leaflet. Results and Discussion Plant Growth The effects of the two wind velocities and two soil moisture regimes on the growth of 80-day-old black walnut seedlings are presented in Table 10 and Figures 19 and 20 (see Tables 17-22 for specific growth measure- ments). Stem.--The higher wind velocity had no signifi- cant effect on the average stem height or diameter but significantly decreased the average oven-dry weight of the stem by 17 percent. The lower soil moisture regime significantly decreased the average stem height and diameter by 18 percent and the average oven-dry weight of the stem by 45 percent. 66 .Aunmflu Hommsv m paw .Aumoa mappfiev N .Auoucoo EouDOQV H mm poamammmao monsuuomm Hmumeoum £ua3 mafia Iooom DDQH83 Moman mo oommnsm mama Hozoa mo o>wufimom oumuoom omoasaaoo mo BQMHOODOQQOHOHZII.mH ousmflm 67 I98 53/ .C U 68 TABLE 10.—-Growth response of 80-day-old black walnut in two wind velocities and two soil moisture regimes.* Wind Velocity Growth Parameter <0.1 m/sec. Wind Velocity 2.8 m/sec. Low Soil High Soil Low Soil High Soil Moisture Moisture Moisture Moisture Regime Regime Regime Regime Stem a b . a b Height (cm) 22.0 25.6 19.1 25.1 Stem Diameter at a b b 1 cm Height (cm) .46 .55 .45a .54 Stem Diameter at a b a b 2.5 cm Height (cm) .40 .49 .38 .49 Stem Dry Weight (g) 1.39a 2.34b 1.05c 2.05d Total Le f Area (cm?) 541a 1133b 459a 968b Average Leaflet a b c d Length (cm) 5.2 7.3 4.6 6.6 Average Leaflet a b 2 d Width (cm) 2.6 3.5 2.3C 3.3 Average Number Leaflets 44a 49b 40a 50b Foliage Dry Weight (g) 2.27a 4.62b 1.75c 3.53d Shoot Dry Weight (g) 3.66a 6.96b 2.81c 5.58d Root Dry Weight (g) 5.34a 11.84b 3.99c 9.46d Root/Shoot Weight Ratio 1.36a 1.7210 1.19° 1.67b *Values with the same letter in the superscript are not sig- nificantly different at m = .05. 69 .prnm Eo m anatomy oEflmoH ouspmwoa Hfiow 30H .CQAB nmfln AQV Ugo .oefimon ousumwoa HHom moan .ocflz amen AOL .oEflmoH ousumfloe HHom 30H .pcfls 30H Amy .mEHmoH oHSDmHOE Hfl0m toe: .ch3 30a Amy cw usaamz MOMHQ pHoIhmpIom mo ucoEmoHo>op uoozmII.mH omsmflm 70 71. .AUHHm EU m ”manomv oEHmOH onsumfloe Hfiom 30H .ch3 amen ADV pcm .memoH ohspmAOE HHow roan .pcAB Ema: AOV .oEHmoH muswmfloa Hwom 30H .UQHB 30H Amy .memoH onspweoe HHOm goes .ng3 30a Adv cw DDQH83 MOMHQ UHOIhmpIom mo ucoemoHo>o© uoou was EoumII.ON onsmwm 73 The seedlings in all treatments achieved 90 per- cent of their height growth by the end of the first 16 days in the tunnels and by the 40th day height growth had virtually ceased (Figure 21). This rapid initial growth during the period when the seedlings had a relatively small amount of foliage was probably the result of the utilization of materials stored in the seed. During the first 40 days the average height of the trees growing in the two moisture regimes gradually diverged, becoming significantly different by the 16th day. The interaction between wind and soil moisture regime in seedling height was not significant. Diameter, on the other hand, increased at a rela- tively steady rate throughout the entire 80 day period (Figure 21). The average diameter of the seedlings grow- ing in the two moisture regimes became significantly different by the 24th day. Foliage.--The higher wind velocity significantly decreased the average oven-dry weight of the foliage per seedling by 23 percent, the average leaf area per seed- ling by 15 percent (8 = .10), and the average length and width of individual leaflets by 11 percent and 7 per- cent respectively. The lower soil moisture regime significantly decreased the average oven-dry weight of the foliage per seedling and the average leaf area per 74 Figure 21.—-Stem height and diameter growth of black walnut seedlings in two wind velocities and two sOil moisture regimes. ---- Low Wind, Low Soil Moisture Regime Low Wind, High Soil Moisture Regime """"' High Wind, Low Soil Moisture Regime --" High Wind, High Soil Moisture Regime 30-‘ Stem Height 25- 20- "———---_—_- 15- lO-a I I I I I T I ‘1 10 20 30 40 50 60 70 80 Days Since Planting '6" Stem Diameter I I I I l I I 1 10 20 30 40 50 60 70 80 Days Since Planting 77 Figure 22.-~Foliar development of black walnut seedlings in two wind velocities and two soil moisture regimes. Low Wind, Low Soil Moisture Regime Low Wind, High Soil Moisture Regime High Wind, Low Soil Moisture Regime High Wind, High Soil Moisture Regime 1200— 1000— CH1 CH1 800- 600- 400--I 200-_ It Leaf Area I I I I I I l I 10 20 30 40 50 60 70 80 Days Since Planting Average Leaflet Width ——— 4"— ’ ...t.‘..oouoooluooou / l..o¢ /" {.0 ,0 Number of Leaflets IIIIIIII 10 20 30 40 50 60 70 80 Days Since Planting Ln 0 l Ibo O 1 30-1 M O l lO-a Average Leaflet Length .-..- I-lI-IDI-I ""“‘IIIIIUIIIIIII u 0" I I I I I I TF'1' 10 20 30 40 50 60 70 80 Days Since Planting Number of Leaflets ‘..,-.u- Ill IIIIIII Imus-II!" I* I I I I I‘“T"1 10 20 30 4050 6070 80 Days Since Planting 79 decreasing 56 percent in the low soil moisture regime while the average oven-dry weight of the shoot decreased only 48 percent. The tap root of every seedling exhibited the double bend seen in the seedlings in Figure 22. This deformation resulted from the germinating nuts being oriented in the soil in such a way that the radicle emerged from the side rather than the bottom of the nut. The emerging radicle grew horizontally for a short dis- tance before turning downward. In summary, the growth of first year black walnut seedlings was significantly decreased both by exposure to a constant ll-hour-per-day wind of 2.8 m/sec velocity and by being subjected to a soil moisture regime attain- ing approximately 7 atm. of soil water suction. The depressed growth of the walnut seedlings in wind agrees, in general, with the results obtained by Satoo (1962) for black locust seedlings Robinia pseudoacacia. The growth reductions in response to wind velocities averag- ing between 3.5 and 3.7 m/sec reported by Satoo were, however, much greater than those observed in this experi- ment and included a substantial reduction in height growth. Growth response differences in the two experi- ments may be due both to the differences in wind veloci- ties maintained and/or to differences in the way the two species respond to wind. 80 Growth reduction in response to the lower soil moisture regime is in agreement with results demonstrat- ing that plant growth can be significantly reduced by reductions in soil moisture content which are still within the range of "available soil water" (Glerum and Pierpoint, 1968; Jarvis and Jarvis, 1963a; Kaufmann, 1968; Miller, 1970; Miller, 1965; Sands and Ritter, 1959; Stanhill, 1957; Steinbrenner and Rediske, 1964; Stransky and Wilson, 1964). Such results disagree with the earlier View supported by Veihmeyer and Hendrickson (1950) that reductions in soil water content do not significantly reduce plant growth until the soil water content is re- duced to very near the "permanent wilting percentage." One reason for this disagreement may be that Veihmeyer and Hendrickson's conclusion was based almost entirely on field experiments while the majority of the experi— ments referred to above were carried out with potted plants. The use of potted plants allows considerable control over and/or monitoring of the soil water status throughout the entire plant root system. In the field, on the other hand, determining the soil water status throughout the plant's root system is difficult because of Spatial variations in the soil's water content and physical properties and problems in defining the extent of the plant's root system. 81 One point of difference between the results of this study and previous studies is the 25 percent de- crease in the root/shoot ratio in the lower soil moisture regime. Previous work on jack pine (Miller, 1970), ponderose pine (Steinbrenner and Rediske, 1964), and sunflower (Whitehead, 1963) indicates that the root/ shoot ratios of these species increases when they are grown at lower soil moisture levels. Despite the differ- ences in rooting habit of walnut and these species, no explanation can be offered at the present time for this difference in response. Transpiration and Stomatal Aperture It is generally believed that wind affects trees primarily by causing mechanical injury and by affecting their transpiration rate (Satoo, 1962). Mechanical injury may lead to mutual shading of leaves due to crown deforma- tion and/or a loss of photosynthetic surface due to the shredding or destruction of leaves (Schneider, gE_gl., 1970). An increase in the transpiration rate could lead to a decrease in the tree's water potential sufficient to interfere with physiological processes or cause par- tial or complete stomatal closure. Closure of the stomata beyond a certain size would result in a decrease in photosynthesis due to a reduction in the rate of carbon dioxide diffusion into the leaf. 82 Little mechanical injury occurs at low wind veloci- ties. The only evidence of mechanical effects observed in this study was a slight deflecting of the branches away from the direction from which the wind blew on the seed- lings exposed to the higher wind velocity. Transpiration from a plant may occur either through the cuticle or through the stomata. When the stomata are Open there is generally less resistance to transpiration through the stomatal pathway than through the cuticular pathway and a high proportion of the trans- piration occurs along that path (Slatyer, 1967). The "driving force" of stomatal transpiration is the vapor pressure gradient which exists between the air in the intercellular Spaces of the leaf and that of the external air. The resistance to the diffusion of water vapor along this pathway is composed of (1) resistance within the leaf, composed of mesophyll resistance, intercellular Space resistance, and stomatal pore resistance, and (2) resistance external to the leaf, which is the resistance to diffusion across the boundary layer of still air at the leaf's surface (Meidner and Mansfield, 1968; Slatyer, 1967). Wind may initially affect the transpiration of a plant in two ways. First, it may decrease the thickness of the boundary layer thereby reducing the external resistance to diffusion. The result of this is to 83 increase transpiration. Second, it may decrease the temperature difference between the leaf and air which re- sults in a less steep vapor pressure gradient between the leaf and air. This results in a decrease in the trans- piration rate. The net effect on transpiration of these two effects of wind depends on the wind velocity, the relative importance of the leaf and external diffusion resistances, and the amount of radiant heating of the leaf occurring (Salisbury and Ross, 1969). In addition, if the wind initially causes increased transpiration, this may result in a decrease in the plant water potential sufficient to cause partial or complete stomatal closure resulting in reduced transpiration. Soil water content also affects the internal water status of a plant--in general, the lower the soil water potential the lower the plant water potential. As observed above, a decrease in a plant's water potential may interfere with physiological processes and/or may cause a decrease in the stomatal apertures which could result in reduced carbon dioxide diffusion and photo- synthesis. For a particular species, the soil water potential at which a particular plant potential results depends, in part, upon the aerial environmental condi- tions. An environment conducive to high rates of trans- piration will cause lower plant water potentials to develop (in a given amount of time) at a particular 84 soil water potential than one which favors low transpira- tion rates. The results of the transpiration and stOmatal aperture measurements from this study are presented in Tables 11 and 12. Wind significantly increased the aver- age transpiration rate at all soil moisture levels by an average of 50 percent but had no significant effect ‘ on the average stomatal aperture. There was no signifi- cant difference in the average transpiration rates or stomatal apertures between the 12 percent and 8 percent soil moisture levels. This corresponds to a 0.2 atm. and a 0.75 atm. soil water suction respectively. How- ever at 4 percent soil moisture, 7 atm. soil water suc- tion, the transpiration rate was, on the average, 70 per- cent less than that at soil moistures of 8 percent or 12 percent and the average stomatal aperture was Signifi- cantly smaller. The increase in average transpiration rate observed at the higher wind velocity agrees with previous reports (Martin and Clements, 1935; Rao, 1938; Satoo, 1962). However, Martin and Clements (1935), working with Helianthus annuus, and Satoo (1962), using Quercus acutissima, both observed considerable decrease in rela- tive stomatal aperture in wind velocities of 2 m/sec to 3 m/sec. Recently, Caldwell (1970), working with Rhododendron ferrugineum and Pinus cembra, has Shown 85 TABLE ll.--Average transpiration rate of black walnut seed- lings during ll hour wind period at 12, 8, and 4 percent soil moisture content.* Soil Moisture Level Wind Velocity 12 8 4 ------ g/dmZ/hr---—- Low .34a .34a .10° High .52b .47b .lGd *Values with the same letter in the superscript are not sig- nificantly different at a = .05. ' TABLE 12.--Relative stomatal aperture of black walnut seed- lings after 11 hours of wind at 12, 8, and 4 percent soil moisture content.* Soil Moisture Level Wind Velocity 12 8 4 Low 2.55a 2.55a 2.36b High 2.57a 2.52a 2.31b *Values with the same letter in the superscript are not sig- nificantly different at a = .05. 86 that the transpiration and stomatal response of different species to wind may be very different. Under the condi- tions prevailing in the wind tunnels, a wind velocity of 2.8 m/sec does not appear to be sufficient to cause a stomatal response in black walnut seedlings detectable after ll hours. The decreases in transpiration and stomatal aper- ture observed at 4 percent soil moisture content (7 atm. suction) agree with the general theory of the effects of decreasing soil water content on transpiration and stomatal aperture as briefly described above. At some soil moisture content, less than 8 percent (0.75 atm. suction) but greater than 4 percent (7 atm. suction), the stomata began to close and the transpiration rate began to decrease. It should be noted that these two events need not have occurred at the same soil moisture content or suction. Decreases in transpiration rate with decreasing soil water content or potential have been reported by several researchers (Cox and Boersma, 1967; Jarvis and Jarvis, 1963a; Jarvis and Jarvis, 1963b; Pessin, 1938; Slatyer, 1957). Decreases in stomatal aperture with decreasing soil water content or potential have been reported by Cox and Boersma (1967) in Trifolium repens and Satoo (1962) in Quercus acutissima. Based on these results, the reduced growth of the black walnut seedlings exposed to the 2.8 m/sec wind 87 velocity cannot be explained by decreases in stomatal aperture resulting in a reduction in the rate of carbon dioxide diffusion and photosynthesis. Perhaps the increased transpiration rate of these plants resulted in the development of a lower plant water potential which, while not low enough to induce stomatal response, in some way affected one or more plant processes involved in growth. It is possible, however, that the reduced growth of the seedlings in the low soil moisture regime may have resulted, at least in part, from the decrease in stomatal aperture causing a reduction in the carbon dioxide diffusion rate and photosynthesis. In addition, it is also possible that the lower soil water potential caused lower plant water potentials to develop which affected one or more of the plant processes involved in growth. CHAPTER IV SUMMARY AND CONCLUSIONS This study was designed to examine the growth response of black walnut to (l) the influence of wind barriers on field planted seedlings and (2) the effects of a controlled environment where wind velocity approxi- mates that to which field grown black walnut seedlings are normally exposed. The influence of wind barriers on first-year black walnut seedlings was examined by comparing the growth response and microenvironment of seedlings grow- ing on the leeward side of wind barriers with that of seedlings growing in adjacent unprotected areas. The study was initiated on May 16, 1970, when the germinat- ing walnut seed was planted, and ended during the week of September 15, 1970, when the seedlings were harvested. During this time various climatic and edaphic factors were monitored in both protected and exposed plots. Seedling stem height and diameter were measured every 2-3 weeks and, at the end of the study, the seedling stem height, stem diameter, total leaf area, oven-dry weight of stem, foliage, and root, and depth of root penetra- tion were determined. On September 2, 9, 10, and 11 the 88 89 xylem sap tensions of the seedlings in both the exposed and protected plots were measured throughout the day with a pressure bomb to determine if the wind barriers had any effect on the seedling's internal water status. The wind barriers considerably affected the microenvironment and growth of the black walnut seed- lings. The wind velocities in the protected plots were reduced to 33 percent of those in the exposed plots. The total solar radiation received by the seedlings in the protected plots averaged 82 percent of that received in the exposed plots. This reduction in radiation did not occur equally on all days but was greater on relatively clear days than on overcast days. Maximum air tempera- tures averaged 2.9°C higher and minimum air temperatures l.6°C higher in the protected plots. On clear days the air temperature in the protected plots was several de- grees higher in the morning and early afternoon and lower in the middle and late afternoon than the temperature in the exposed.plots. On overcast days the temperatures in the exposed and protected plots were quite similar throughout the day. There was no significant difference between the exposed and protected plots in the atmospheric relative humidity or the average temperature or moisture content of the upper 15 cm of soil. All of these effects can be explained by the effects of the barrier in reduc- ing the wind movement in the protected plots and/or 90 shielding the protected plots from the greater proportion of the solar radiation from the western sky. The presence of the wind barriers increased the size of the black walnut seedlings in all growth param- eters measured except depth of root penetration (Table 13). The root/shoot weight ratio of the seedlings in the protected plots was 22 percent less than that of the seedlings in the exposed plots. The increased seedling size in the protected plots was due, in part, to greater height growth on the protected plots throughout the growing season and a significantly greater height and diameter growth rate in the protected plots after August 3. Leaf senescence was evident on the seedlings in the exposed plots by the latter part of August while seedlings in the protected gflrpts showed little evidence of senescence by mid September. This early senescence of the leaves in the exposed plots may be related to the decline in growth rates observed in the exposed plots. Observation of the xylem sap tension of the seed- lings during September indicated that in both the pro- tected and exposed plots it rose rapidly following sun- rise until around midday when the rate of change became relatively slow. This plateau was maintained until around 4:00 p.m. when the tension began to decrease. There was no significant difference in the xylem sap 91 TABLE l3.--Comparative growth response of lS-week-old black walnut in exposed and protected field plots.* Growth Parameter Growth Increase in Protected Plots % Stem Height 15 Stem Diameter 14 Stem Dry Weight 46 Total Leaf Area 85 Average Leaflet Length 12 Average Leaflet Width 9 Average Number of Leaflets 46 Foliage Dry Weight 158 Shoot Dry Weight 110 Root Dry Weight 27 Total Dry Weight 47 *Significant at at least a = .10. 92 tensions in the protected and exposed plots during the "plateau period" indicating that the wind barriers had no effect on the tensions during this time. Further study is needed to determine if this is true at all times of the day and growing season and under different en- vironmental conditions. The effects of wind under controlled environ- mental conditions were studied by examining the growth responses of germinating black walnut seedlings for 80 days under two wind velocities (<0.1 m/sec or 2.8 m/sec) and two soil moisture regimes (12 percent drying to 8 percent or 12 percent drying to 4 percent). All other environmental factors were maintained at levels within the range of natural conditions. The growth response of the seedlings to the treatments was examined by periodically measuring the stem diameter,‘stem height, and the leaf area of each seedling and determining the oven-dry weights of the seedling leaves, stem, and roots at the conclusion of the study. The transpiration rates and average stomatal aperture were determined during the last 20 days of the study for each seedling at 12 percent, 8 percent, and 4 percent soil moisture after 11 hours of exposure to its wind treatment. The effects of the two wind velocities and soil moisture regimes on the black walnut seedlings are 93 summarized in Table 14. Exposure to the higher wind velocity had no significant effect on seedling stem height, stem diameter, or number of leaflets but signifi- cantly reduced all other growth parameters measured. There was no significant difference between the root/ shoot weight ratio in the two wind treatments. The low soil moisture regime caused a decrease in all observed growth parameters and significantly reduced the root/ shoot weight ratio by 25 percent. The growth reductions caused by the lower soil moisture regime were greater in all parameters measured than those caused by the higher wind velocity. No differences were observed in the height and diameter growth patterns between seedlings in the high and low wind velocities or between those in the high and low soil moisture regimes. Exposure to the higher wind velocity signifi- cantly increased the average transpiration rate at all soil moisture levels by an average of 50 percent but had no significant effect on the stomatal aperture. The transpiration rates and stomatal apertures at 12 percent and 8 percent soil moisture content were not signifi- cantly different. However, at 4 percent soil moisture content the transpiration rate was 70 percent less than that at 8 percent or 12 percent and the average stomatal aperture was significantly smaller. 94 TABLE l4.--Comparative growth response of 80-day-old black walnut in two wind velocities and two soil moisture regimes.* Growth Decrease Growth Decrease Growth Parameter (High Wind (Low Soil -_Ysiesifzi _____ %-¥3§§EE£E_§EE£TE> Stem Height n.s. 18 Stem Diameter n.s. 18 Stem Dry Weight 17 45 Total Leaf Area 15 52 Average Leaflet Length 11 30 Average Leaflet Width 7 30 Average Number of Leaflets n.s. 18 Foliage Dry Weight 23 52 Shoot Dry Weight 21 48 Root Dry Weight 22 56 Total Dry Weight 21 53 *Differences significant at a = .05. 95 Based on the transpiration and stomatal aperture data, the reduced growth of the black walnut seedlings exposed to the 2.8 m/sec wind velocity cannot be explained by decreases in stomatal aperture causing a reduction in the rate of carbon dioxide diffusion and photosynthesis. Perhaps the increased transpiration rate of these plants resulted in the development of a lower plant water potential which, while not low enough to induce stomatal reSponse, affected one or more of the plant growth pro- cesses. It is possible, however, that the reduced growth of the seedlings in the low soil moisture regime may have resulted, at least in part, from the decrease in stomatal aperture. It is also possible that the lower soil water potential caused lower plant water potentials to develop which influenced one or more of the plant growth pro- cesses. In summary, the results of these two studies indicated (1) that a constant wind velocity, approximat- ing the average wind velocity that naturally growing black walnut seedlings are normally exposed to, can cause significant decreases in the seedling's growth and (2) the use of wind barriers to reduce the force of wind striking black walnut seedlings will result in signifi- <:ant increases in the seedling's growth. In addition to :reducing wind movement, the barriers also affect solar :radiation, air temperature, and, undoubtedly, soil sur- :face temperature. LITERATURE CITED 96 LITERATURE CITED Anonymous. 1961. Metea soil series description. National COOperative Soil Survey, U.S.A. 2 pp. Baten, W. D. and A. H. Eichmeier. 1951. A summary of weather conditions at East Lansing, Michigan prior to 1950. Mich. St. Col., Agric. Exp. Sta. 63 pp. Begg, J. E., J. F. Bierhuizen, E. R. Lemon, D. K. Misra, R. O. Slatyer, and W. R. Stern. 1964. Diurnal energy and water exchanges in bulrush millet in an area of high solar radiation. Agric. Met. 1: 294-312. Caldwell, M. 1970. Plant gas exchange at high wind speeds. Plant Physiol. 46: 535-537. Carpenter, Stanley B. 1971. Developmental changes in assimilation and translocation of photosynthate in black walnut (Ju lans ni ra L.) and honeylocust (Gleditsia triacant 05 L. seedlings. PhD. dis- ' sertation, Mich. St. Univ. Cliff, E. P. 1966. The increasing challenge of decreasing quality. pp. 1-3. £2_Black walnut culture. N. Cent. For. Exp. Sta., St. Paul, Minn. No series. 94 pp. Cox, L. M. and L. Boersma. 1967. Transpiration, soil temperature, and water stress. Plant Physiol. 42: 550-556. Dirmhirn, I. 1953. Zur Strahlungsminderung an Windschutz- streifen. Wetter und Leben 5: 208-213. Finnel, H. H. 1928. Effect of wind on plant growth. J. Amer, Soc. Agron. 20: 1206-1210. Fourt, D. F. 1968. Sitka spruce, shelter and moisture. Res. Developm. Pap. For. Comm., Lond., No. 72. 8 pp. (Forestry Abs. 30: 430. No. 3647). Fowells, H. A. 1965. Silvics of forest trees of the United States. U.S.D.A. Handbook No. 271: 203-207. 97 98 Geiger, R. 1966. The climate near the ground. Harvard Univ. Press, Cambridge, Mass. Glerum, C. and G. Pierpoint. 1968. The influence of soil moisture deficits on seedling growth of three coni- ferous species. For. Chron. 44: 26-29. Gloyne, R. W. 1965. Some characteristics of the natural wind and their modification by natural and artifi- cial obstructions. Sci. Hort. 17: 7-19. Hill, L. 1921. The growth of seedlings in wind. Royal Society Proc., B, 92: 28-31. Hogg, W. H. 1965a. Measurement of the shelter effect of land forms and other topographical features and of artificial windbreaks. Sci. Hort. 17: 20-30. . 1965b. Report on work at experimental horti- culture stations with shelter screens. Sci. Hort. 17: 61-66. Jarvis, P. G. and M. S. Jarvis. 1963a. The water relations of tree seedlings. I. Growth and water use in relation to soil water potential. Physiol. Plant. 16: 215-235. . 1963b. The water relations of tree seedlings. II. Transpiration in relation to soil water poten- tial. Physiol. Plant. 16: 236-253. Jaynes, R. A. 1969. Handbook of North American nut trees. W. F. Humphrey Press, Inc., Geneva, New York. Kaufmann, M. R. 1968. Water relations of pine seedlings in relation to root and shoot growth. Plant Physiol. 43: 281-288. Khattak, G. M. 1968. Early response of planted black wal- nut to site modification. Ph. D. Dissertation, Mich. St. Univ. Lausher, F. 1934. Warmeausstrahlung u. Horizonteinengung. Sitz-B Wien. Akad. 143: 503-519. (Cited by Geiger, R. 1966. The climate near the ground. Harvard Univ. Press, Cambridge, Mass.). Martin, E. V. and F. E. Clements. 1935. Studies of the effect of artificial wind on growth and transpira- tion in Helianthus annuus. Plant Physiol. 10: 613-636. ' 99 Meidner, H. and T. A. Mansfield. 1968. Physiology of stomata. McGraw-Hill Book Comp., New York. Metcalf, W. 1936. The influence of windbreaks in pro- tecting citrus orchards. J. For. 34: 571-580. Miller, Elwood L. 1970. Studies of environmental factors affecting jack pine (Pinus banksiana Lamb.) re- generation. Ph.D. Dissertation, Mich. St. Univ. Miller, L. N. 1965. Changes in radiosensitivity of pine seedlings subjected to water stress during chronic gamma irradiation. Health Phy. 11: 1653-1662. Pessin, L. J. 1938. Effect of soil moisture on the rate of growth of longleaf and slash pine seedlings. Plant Physiol. 13: 179-189. Quigley, K. L. and R. D. Lindmark. 1966. Timber resources. - pp. 6-12. In Black walnut culture. N. Cent. For. Exp. Sta., St. Paul, Minn. No series. 94 pp. Randall, C. E. 1967. Black walnut, our vanishing money tree. Amer. For. 73(10): 14-17, 38-40. Rao, V. P. 1938. Effect of artificial wind on growth and transpiration in the Italian millet, Setaria italica. Bull. Torrey Bot. Cl. 65: 229-232. Read, R. A. 1964. Tree windbreaks for the central Great Plains. U.S.D.A. Agri. Handbook No. 250. 68 pp. Rennie, P. J. 1956. The importance of shelter to early tree growth on upland moors. Forestry 29: 147-153. Sampson, Joan. 1961. A method of replicating dry or moist surfaces for examination by light microscopy. Nature 191: 932-933. Salisbury, F. B. and Cleon Ross. 1969. Plant physiology. Wadsworth Publ. Comp., Inc., Belmont, Calif. Sands, K. and A. J. Rutter. 1959. Studies in the growth of young plants of Pinus sylvestris L. II. The relation of growth to soil moisture tension. Ann. Bot. (NS) 23: 269-284. Satoo, T. 1962. Wind, transpiration, and tree growth. pp. 299-310. In Tree growth (Ed. T. T. Kozlowski). The Ronald Press Comp., New York. lOO Schneider, G., G. Khattak, and J. N. Bright. 1970. Modi- fying sites for the establishment of black walnut. pp. 155-169. In Proceedings of the Third North American Forest Soils Conference. (Editors C. T. Youngberg and C. Davy). Oregon St. Univ. Press, Corvallis, Oregon. Scholander, P. F., H. T. Hammer, E. D. Bradstreet, and E. A. Hemmingsen. 1956. Sap pressure in vascular plants. Science 148: 339-346. Slatyer, R. O. 1957. The influence of progressive in- creases in total soil moisture stress on transpira- tion, growth, and internal water relations of plants. Aust. J. Biol. Sci. 10: 320-336. . 1967. Plant-water relationships. Academic Press, New York. Stanhill, G. 1957. The effect of differences in soil- moisture status on plant growth: a review and analysis of soil moisture regime experiments. Soil Sci. 84: 205-214. Steinbrenner, E. C. and J. H. Rediske. 1964. Growth of ponderosa pine and Douglas-fir in a controlled en- vironment. Weyerhaeuser For. Pap. No. 1. Centralia, Wash. 31 pp. Stoeckeler, J. H. 1962. Shelterbelt influence on Great Plains field environment and crops. U.S.D.A. Production Research Report No. 62. 26 pp. Stransky, J. J. and D. R. Wilson. 1964. Terminal elonga- tion of loblolly and shortleaf pine seedlings under soil moisture stress. Proc. Soil Sci. Soc. Amer. 28: 439-440. Veihmeyer, F. J. and A. H. Hendrickson. 1950. Soil moisture in relation to plant growth. Ann. Rev. Plant Physiol. 1: 285-304. Wadsworth, R. M. 1959. An optimum wind speed for plant growth. Annals Bot. (NS) 23: 195-199. Waring, R. H. and B. D. Cleary. 1967. Plant moisture stress: evaluation by pressure bomb. Science 155: 1248-1254. Weatherly, P. E. 1950. Studies in the water relations of the cotton plant. II. Diurnal and seasonal vari- ations in relative turgidity and environmental factors. New Phytol. 50: 36-51. lOl Whitehead, F. H. 1957. Wind as a factor in plant growth. pp. 84-95. In Control of the plant environment. (Ed. J. P. Hfidson). Acad. Press, Inc. New York. . 1962. Experimental studies of the effect of wind on plant growth and anatomy. II. Helianthus annuus. New Phytol. 61: 59-62. . 1963. Experimental studies of the effect of wind on plant growth and anatomy. IV. Growth sub- stances and adaptative anatomical and morphological changes. New Phytol. 62: 86-90. Whitehead, F. H. and R. Luti. 1962. Experimental studies Wilson, Winter, Zelitch, of the effect of wind on plant growth and anatomy. I. Zea Mays. New Phytol. 61: 56-58. C. C., W. R. Boggess, and P. J. Kramer. 1953. Diurnal fluctuations in the moisture content of some herbaceous plants. Am. J. Bot. 40: 97-100. E. J. 1965. Some effects of wind upon vegetable crOp plants. Sci. Hort. 17: 53-60. I. 1961. Biochemical control of stomatal opening in leaves. Proc. Natl. Acad. Sci. 47: 1423-1433. APPENDIX 102 103 mm mma hm m.va mm com Hm.H mum mm. mm.a ma. ms.m musumfloz swam .wcH3 swam om mmH ms «.0H mm How om.H mom am. mm.a ma. ow.m musumfloz 30a .naflz swam mm «ma we s.oa vs mos mm.H mmm mm. .Hm.H ma. mm.m musumfloz Bonn .maflz 305 on oma ms ~.a on mes mm.a mew am. «H.H ma. mm.m musumfloz 30A .pcflz BOA lllllllllllllllllllll Email:IIIIIIIIIIIIIIIIIII Illlllllulwulunullll Hm as m so mm :2 mo mz m: s m z ucmsummue ucmfluusz , .mosum ucmficoufl>cm poaaouucoo CH uncamz xomHQ paOuhmplom mo mflmhamcm ucmfluusc HMHHOMII.mH mqmde owm Hm m.am m.m mma mmm ms.a Hmm mm. mm. Hm. mm.~ scam ammomxm Hem mm a.mm ~.HH mma mmm mm.a «mm mm. mm. am. mm.m uoam wmnomuonm nuuuuunuunuunnny ..... sad uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu w nnnnnnnnn H< cm m so mm a: mo mz 8: s m z ucmsummue ucmwuusz .swsum camflm an panama soman caouxmmzuma no mammamcm usmfluusc mafiaomll.ma mqmsm pwaaonucoo CH mwcfiapomm uncamz xoman mo Davao: EU H um Hmumsmflp Emum mmmum>m DapOwnmmll.mH mamfie m.m~ m.m~ w.NN a.mm m.- >.mm v.~m v.am v.om m.ma m.m musumwoz Hfiom soar .scflz nmflm m.oH a.ma m.ma o.wa m.ma v.oH m.oH a.mH m.ma a.ma m.m musumfloz HHom 30A .waaz swam a.mm o.mm o.mm a.mm a.mm h.m~ v.~m N.Hm m.mH m.ma m.m ousumfloz HHom swam .pzflz 3oq m.mH m.ma m.ma m.mH m.mH m.mH a.ma a.ma m.pa m.va m.m musumfioz HHom 304 .UGHK 30a lllllllllllllllllllllllllllllllllll EOIIIIIIIIIIIIIIIlllllllllllllllllll om Nb vw om mv (ow mm vm ma m o unmaummue mafiucmam mocflm m>m0 .hpsum ucmEcoufl>co Umaaonucoo Ga mmcflapmom uncams xoman mo unmflmn Emum mmwuo>m oprMHmmlu.mH mamqs 105 ow.m 04.m um.m mm.m hm.e mm.m mm.4 musumfioz 440m swam .vcflz Hafiz vo.v mv.¢ ov.v m4.v 45.m m4.m vw.4 musumwoz 440m 304 .ncflz nmfim mm.h 4m.m mv.m wv.m mw.v mv.m om.4 musumaoz 440m nmflm .pcflz 304 «m.m om.v ~m.v on.v mm.m nm.m mm.4 musumwoz 440m 304 .UGHS 304 llllllllllllllllllllllll EOIIIIIIIIIIIIIIIIIIIIII bm \mv ov mm on ma m usmsummue mafiuCMHA moswm mama .mpsum ucmEcou4>cw p0440uus00 cw mmcflapwom usch3 xomHQ mo £DOC04 004m004 mmmum>m 04604H0m||.om W4m¢e a.mom m.q~m a.mmm m.45o o.mmv w.omm a.mm musumfloz 440m nmfim .ocflz nmflm h.mhv a.m4v 4.5mm 4.mmm m.vvm m.om4 m.mm mnoumfloz 440m 304 .waaz nmflm m.mm44 «.mVOH 4.44m n.8mm 4.mov m.ovm 4.mm ousumfloz 440m swam .psflz 304 c.4vm n.44m m.vmv m.vmm m.mom 4.mo~ m.vm musumfioz 440m 304 .psflz 304 . nnnnnnnnnnnnnnnnnnnnnnn NEU nnnnnnnnnnnnnnnnnnnnnn om mv ohm mm vm 04 m usmEumwuB mCHDCMHm mocflm mhmo .hpsum ucmEc0H4>cm p044ouucoo C4 mmC44Umom usc4m3 xUmHQ mo moum mm04 mmmuo>m oflooflummnl.m4 m4mde mm mm mm Hm sq NV mm musumaoz 440m nmfim .ocnz roam 04 mm mm mm mm mm mm musumfloz 440m 304 .ccaz sons me as av as we mm mm musumfioz 440m nmfim .0243 304 «4 sq as as as mm mm musumnoz 440m 304 .6043 304 lllllllllllllllllllllllll *Illlllllllllllllllllll om, ms ow mm (sm mHI m ucmsummne mGHDCMHA mocflm mama .xpsum ucmficouw>cm U0440uuc00 CH mmcfi4pmmm usch3 x0044 mo m004m004 m0 umbesc mmmu0>m oapoflummll.mm m4m48 106 mm.m oo.m mm.m nm.m mm.m vs.4 mm. musumfloz 440m 5043 .mcflz sons mm.m mm.m >4.m vo.m om.4 mm.4 mm. mnsumfloz 440m 304 .ccflz :mflm mm.m mm.m no.m mm.m m4.m ow.4 4m. ousumfloz 440m swam .UC43 304 mm.m mv.m sm.~ mm.m mm.4 vm.4 mm. musumfloz 440m 304 .UCHB 304 llllllllllllllllllllllll EUIIIIIIIIIIIIIIIIIIIIII om mw ow mm vm wH. m usmEummuB mcHDCM4m mocflm whoa .wpsum ucoficou4>cm p0440uucoo :4 mm244©0wm usc4m3 x0040 wo sup43 D04w004 wmmum>m 04p04u0m1|.4N M4449 GRN STRTE UNIV. ll) IBWIIHWII‘BNIHLIEWHI lllallllllll'lHlHLHIHI