WATER RELATIONSHIPS OF HONEY MESQUITE (PROSOPIS GLANDULOSA TORR. VAR. GLANDULOSA)
SAMMY JOE EASTER, B.S.
A THESIS IN RANGE SCIENCE
Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Approved
Accepted
Díealh of tl^ Gradukte School
May. 1973 AC 80 S T3 1573
ACKNOWLEDGMENTS
My sincere appreciation is extended to Dr, Ronald E. Sosebee for his unselfish expenditure of time, dedicated guidance, and continuous support throughout the study. Also, I would like to thank Dr, Billie E« Dahl, Dr. Russell D. Pettit, and Dr. Joe R. Goodin for their helpful comments and timely suggestions.
Special appreciation is extended to Dr. Ray Brovm for his help and suggestions on the calibration techniques of the thermocouple psychrometers and porometer and Elaine Holmes for her help on the illustrations. A very special thanks goes to my wife, Sara, and my family for their patience and support; without their help and encouragement this would not have been possible.
11 TABLE OF CONTENTS
ACKNOWLEDGMENTS ii LIST OF TABLES V LIST OP FIGURES vi I. INTRODUCTION 1 II. LITERATURE REVIEW . 3 III. METHODS 11 IV. RESULTS AND DISCUSSION 19 Soil Water Relationships. 19 Plant Water Relationships 22 Atmospheric Water Relations and Transpiration. • • . 29 V. SUMMARY AND CONCLUSIONS 35 LITERATURE CITED 38 APPENDIX 42 A. MODAL DESCRIPTION OF THE AMARILLO FINE SANDY LOAM SOIL SERIES 43 B. CALIBRATION INSTRUCTIONS FOR THERMOCOUPLE PSYCHROMETERS 44 C. CALIBRATION INSTRUCTIONS FOR THE LAMBDA POROMETER 4? D. RELATIONSHIP OF ATMOSPHERIC WATER POTENTIAL AND TRANSPIRATION RATES FROM HONEY MESQUITE TREES GROWING UNDER IRRIGATION 52
iii E. RELATIONSHIP OF ATMOSPHERIC WATER FCTENTIAL AND TRANSPIRATION RATES PRCN' HOiiEY KESQUIT" TREES GRÛWING UNDER NON-IRRIGATIO: 53 F. DAILY ENVIRÛNMÎNT. PLANT WATiR PÛTENTIALS. AND TRANSPIRATION THAT EXISTED CN THE IRRIGATED SITE Or ThE STUDY OP Y^SiUITE WATER RELATIONSHIPS 54 G. DAILY ENVIRONMENT. PLANT WATr^R POTENTIALS, AND TRANSPIRATION THAT EXISTED ÛN ThE NON- IRRIGATED SITE OF ThE STUDY ÛF MES^UIT-^ WATER RELATIÛNSHIPS 56 H. NAME OF EQUIPMENT USED AND ADDRESSES FROM WHICH THEY WERE OBTAINED 58
iv LIST OF TABLES
Table 1. Average water potentials of the gradient from the soil through the plant into the atmosphere throughout the day on the irrigated site of the study of soil«plant water relationships of honey mesquite. •..«.•.....••• 24
2» Average water potentials of the gradient from the soil through the plant into the atmosphere throughout the day on the non-irrigated site of the study of soil-plant water relationships of honey mesquite^ . .••••••• 25 LIST OF FIGURES
Figure
!• Diagrara of a double-junction Spanner thermocouple psychrometer used in the study of soil-plant water relationships of honey mesquite •••••• 13 2^ Installations of thermocouple psychrometers at three different positions in each tree for plant water potential determinations on the irrigated and non-irrigated site of the study of soil-plant water relationships of honey mesquite. • • • • 14 3^ Measurement of soil water potential with the Spanner thermocouple psychrometers and the S-B Systems microvolt meter ...... •••••• 16 4^ Measurement of plant water potential with the Spanner thermocouple psychrometers and the S-B Systems microvolt meter •••••••••••••• 1? 5» Diffusion porometer used to measure transpiration rates in honey mesquite • • • 18 6. Average soil water potential at various depths for the irrigated and non- irrigated site June 1 through August 28, 1972, in the study of soil-plant water relationships of honey mesquite^ ...••••••••••• 20 7, Average soil water content at various depths for the irrigated and non- irrigated site June 1 through August 28, 1972, in the study of soil-plant water relationships of honey mesquite^ ••...••••••••• 21
vi 8. The relationship of soil water potential (bars) to soil water content (^) at four depths on the non-irrigated site in the study of soil-plant water relationships of honey mesquite 23 9t Correlation of time of day and water potential at three positior.s in honey mesquite trees growing under irrigated conditions 27 10. Correlation of time of day and water potential at three positions in honey mesquite trees growing under non-irrigated conditions 28 11. Relationship of time of day and transpiration rates of trees growing on the irrigated and non-irrigated site in the study of soil-plant water relationships 32 12. Honey mesquite trees on the irrigated site showing a large number of leaves per tree 34 13. Honey raesquite trees on the non- irrigated site showing fewer leaves per tree 34 14. Thermocouple psychrometer calibration chamber ..... 45 15. Thermocouple psychrometer calibration chamber illustrating position of the moistened filter paper 45 16. Transit time (A t) required per chane^e in microaonperes for various standard diffusion pathleneths (L) of resistance at different teraperatures. ... 48 17. Teraperature dependence of resistance meter sensitivity (S) and of the water vapor diffusivity (D) 50 18. Relationship of leaf resistance (R^) and transit tirae ( A t) 51
vii
IE^M>««l CHAPTER I INTRODUCTION
Honey mesquite (Prosopis glandulosa Torr. var. glandulosa) has infested about 22 million hectares of Texas rangeland to varying degrees. More than I3 million hec- tares of Texas rangeland are covered by moderate to heavy infestations^(Smith and Rechenthin, 1964). Mesquite varies in growth form from large single stem plants to small multiple stem shrubs. Mesquite generally has a well developed root system which may spread about 22 m laterally and extend to a depth of 53 ra (Phillips, 1963). >/parker and Martin (1952) reported that velvet mesquite (ProsoT)is velutina) can eliminate available soil moisture from an area with a radius of 15 m and 60 cm deep for as long as 73 days during the summer in Arizona and thus prevent development of desirable perennial grasses. Mesquite has been reported to use water inefficiently. McGinnies and Arnold (1930) reported that velvet mesquite required 1725 kg of water in the summer to produce a kg of dry matter, whereas perennial grasses such as blue grama (Bouteloua gracilis) and sideoats grama (Bouteloua curtipendula) required only 387 and 550 kg respectively. When water is available. raesquiteuse s it extravagar.tly (Wendt, 1966). Yet it is able to survive during lor.g periods of drought and in areas characterized ty less than 15 cm annual rainfall. Thus mesquite must be adapted to a broad raxige of available soil water. A need exists for fundaraental knowledge of plant-soil water relationships in mesquite growing under field condi- tions. Most past work was with seedlings, while the water relationships of mature trees is yet to te establishei, The objectives of this study were (1) to determine the potential for use of psychrometry to study soil-plant water relationships in honey mesquite, (2) to compare soil water potentials with the soil water content of ain area. (3) to measure diurnal water potential gradients in mature mesquite trees, (4) to compare water relationships in mesquite grown under natural (non-irrigated) environmental conditions to mesquite grown on an area that was irrirated throughout the growing season, and (5) to compare differ- ences in transpiration rates of trees grown in both areas.
"^^ftilSH.''-'. CHAPTER II LITERATURE REVIEW
Mesquite water stress is most often reported to be correlated with percent soil water (Wendt, Hass, and Runkles, I968; Degarmo, I9661 Shimshi, I963). However, an alternate method based on determinations of free energy of water offers many advantages. One advantage of the latter method is that of expressing soil water in terms of the energy required for removal of a unit of water from the soil by plants (Brown, 1970). This energy status has been termed water potential and may be used to describe the state of water in any part of a soil-plant-atmosphere system (Slatyer and Taylor, I960). Stanhill (1957) stated that since plants respond much more closely to the water potential than to the water content of a soil, it is more desirable to know the potential of water than the amount of water in the soil.
Soil water characteristic curves for loam soils indi- cate that approximately 50% of total available water is held at approximately -2 bars, while in sandy soils 7Q% of the total available water is held at tensions less than -2 bars (Woodhams and Kozlowski, 195^)« Thus the available water in the sandy soil is extracted much more quickly through evapotranspiration during periods of high potential evapotranspiration. There has been some disagreement about the degree of availability of water to plants in drying soil over the range from field capacity to permanent wilting percentage. Some workers have reported that water is equally available to plants over the entire range (Magness, Degman, and Furr, 1935í Veihmeyer and Hendrickson, 1950). Others have reported water release curves which strongly suggest an exponential or curvilinear depletion of water as a result of increasing soil-water tension (Zahner and Stage, I966). According to Kramer (1949)» disagreement over the degree of availability of water in drying soil exists partially because of differences in water tension-water content relations for different textural grades of soils. In coarse textural soils water tension changes relatively little from field capacity almost to the wilting percent- age. At that point water tension changes sharply to permanent wilting percentage. The water release curves for fine textured soils do not exhibit this shgarp break, indicating that water is withheld from plants with appreciably greater energy. Taylor (I965) stated that the status of soil water potential nearly always differs among soils of different texture, Measurements of soil water energy have merit because they are more directly comparable among different textural classes (Brown, 1970). Beckett and Dunshee (1932) and Kozlowski (19^9) observed that plant processes are markedly influenced by decreasing soil water. Seasonal growth responses of forest trees and most other woody vegetation are more sensitive to fluctuations in soil water than to any other environmental factor (Kramer and Kozlowski, I960). Shimshi (1963) stated that stomatal aperture, transpira- tion, and photosynthesis were reduced at lower soil water. Martin (19^0) found the stomata to be smaller and more numerous on plants with less available water. Martin also found the leaves were thinner but the relative amount of palisade and spongy mesophyl tissue was the sarae. Anatomically, the cells appeared unable to expand because of reduced turgor rather than a reduction in the number of cells formed. Slayter (1957a) stated that transpiration could be slowed because of the effect of turgescense on stomatal closure.
Because transpiration is primarily a passive phenom- enon it does not necessarily cease at any particular stress level. It could be expected, however, that the transpira- tion would be reduced at high stress levels because of storaata closure and movement of water in.the soil (Slayter, 1957b). Martin (19^0) reported that the rate of transpiration per unit area of leaf was ordinarily affected when about two-thirds of the available soil water had been removed. The actual point where it is affected depends on the transpiration rate. Veihmeyer and Hendrickson (1950) stated that transpiration is unaffected by total soil moisture stress until permanent wilting percentage is reached and then it virtually ceases when the plants gire growing in a field soil. On the contrary Slatyer (1957a) found that a reduction in transpiration rates of cotton first occurred at high water stress but continued at reduced rates when the soil water was below the classical 15 atm total soil moisture stress,
Water in the soil-plant-atmosphere continuum follows a gradient of decreasing free energy from the soil, through the plant, into the atmosphere. At times of high transpir- ation, steep energy gradients may result within small distances from the soil, through the plant, into the atmosphere (Brown, 1970). A quantitative evaluation of water stress can be computed from the amount of water that is actually transpired and from the amount that poten- tially could be transpired if soil water tensions are less than -2 bars (Zahner and Stage, I966). Gardner (I960) emphasized that the status of plant water nearly always differs from that of soil water. Vegetation experiences internal water stress whenever the rate of transpiration exceeds the rate of soil water absorption (Kramer, I962), Water stress in plants occurred even when the soil was at field capacity, but was assumed to be minimal when the soil was at field capacity or losing available water held at tensions of less than -2 bars (Zahner and Stage, I966). In Douglas fir (Pseudotsuga menziesii), water stress reached -20 bars even with soils near field capacity if the radiation load was sufficiently high. Stress in the upper crown of a 24 m tree fluctuated rapidly with an increase of 5 atm/hr, depending upon the atmospheric stress (Waring and Cleary, I967). Cary and Wright (1971) stated that in Southern Idaho, plant water potential is influenced more by the evaporation demand of the atmosphere than by the soil water potential, so long as the soil water is within the range of measurement with the tensiometer. Studies by Slatyer (1955) have shown that plant water potential is directly influenced by evaporation until a critical soil water potential is reached, When soil water potential falls below some critical level, a combination of both atmospheric and soil conditions control the plant water potential. As the soil dries, water stress becomes even greater within plant tissue, depending on the magnitude of the potential evapotranspiration (Zahner and Stage, 1966). In general, the water potential in actively 8 growing plants range between -5 and -30 bars, although under desert conditions potentials may drop to -80 bars (Cary, 1971). Hsieh, Campbell, and Gardner (1971) found values as low as '"^S bars on leaves of woody desert species and -94 bars on leaves of salt grass (Distichles stricta). Scholander et al. (I965) found that halophytes commonly grow at -30 to -60 bars soil water potential. Rawlins, Gardner, and Dalton (I968) found that water potential of plants was always lower than water potential in the soil at the 25 cm depth and the difference was greater during days when the transpiration rates were high than during days when the transpiration rates were low. Scholander et al. (I965) reported a gradient of decreasing water potential with increasing height of Douglas fir and redwood (Sequoia sempervirens) trees. Wiebe et al. (1970) studied water potential from the soil through mature trees of juniper (Juniperus scopulorum Sarg,), elm (Ulmus pumila L.), Russian olive (Elaiagnus angustifolis L.), and maple (Acer glabrum Torr.). He recorded the highest water potentials in the soil (0.1 to 0.3 m depth); they decreased progressively up the tree trunk to the branches and leaves. Thus the water potential gradient decreased continuously from the soil through the trees, into the leaves. Water stress in Douglas fir reached at least -40 bars without permanent injury to the plant (Waring and Cleary, I967). They found that Douglas fir and Shasta fir (Abies magnifica var, shastensis) growing on very shallow sites may be under considerable stress, while nearby trees on deeper soils experienced little stress, Summaries of day to day calculations of weather con- ditions and their effect on water stress are useful not only by individual days, but also when accumulated for logical periods within the growing season and by seasonal trends (Zahner and Stage, I966). Scholander et al. (I965) found that diurnal cycles of water stress in trees of 10 to 20 atm were common, Significant diurnal variations were also found in tobacco (Hoffman and Splinter, I968).
Daily fluctuation in the plant water potential of beans were relatively constant as long as the daily energy flux remained fairly constant and soil water was not limiting (Kanemasu and Tanner, 1969). As soil water became limiting, the magnitude of the daily fluctuation increased and eventually the soil and plant water potential decreased. Internal water stress is more difficult to predict because the status of water within a plant is dependent upon soil water stress, atmospheric stress, and the ability of the plant to control water loss (Slatyer and Gardner, 1965). Plant water potential can be accurately determined by measuring the equilibrium relative humidity over tissue 10
(Wiebe et al, 1970). Spanner (1951) developed a thermocouple psychrometer technique for the measurement of the internal water poten- tial of detached leaves. This technique is based on the Peltier effect. These psychrometers are being increasingly used for determination of leaf water potential in the range of 0 to -50 bairs (Lambert and Schilfgraade, 19^5; Rawlins et al, 1968). Campbell, Tuill, and Gardner (I968) were able to extend this to about -100 bars with special welding techniques and increased cooling time.
Lambert and Schilfgraade (I965) suggested the possi- bility of using thermocouple psychrometers to study water potential gradients and resistance in plants by simultan- eous determinations of the water potential of leaves at different positions along the stalks and at different transpiration rates. Wiebe et al. (1970) used miniature psychrometers to measure water potentials of trees under field conditions and found them to be a versatile and valuable tool in plant and soil water relations research. CHAPTER III METHODS
A study of the water relationships of honey mesquite was conducted on 10 trees at the Research Farm located on the Texas Tech University campus in Lubbock, Texas, Field data were collected March through August, 1972, The soil of the study area was an Amarillo fine sandy loam, It is well drained and slow to moderately permeable from the surface, It is moderately permeable internally (Appendix A), The vegetation within the study area was a combination of grasses, shrubs, and woody plants, The grasses were predominantly blue grama and buffalo grass (Buchloe dactyloides), Broom snake weed (Xanthocephalum sarothrae) was the dominant shrub, Mesquite was the dominant woody species, while catclaw mimosa (Mimosa biuncifera) was a subdominant species. Five trees were selected on two homogenous sites in the same area. One site was irrigated to maintain a soil water potential approximately -1 bar, while the soil water conditions of the other site were determined by the natural environmental conditions, Spanner thermocouple
11 12 psychrometers (Figure 1) were used to determine the water potential at three different positions within each tree (Figure 2), The psychrometers were installed within the tree by drilling a hole into the wood approximately 1 cm, Extreme care was exercised in installing the psychrometers just below the bark so they would be in contact with the current annual rings, Branch installations were placed in the axil of two branches as described by Wiebe (1970), Silicone vacuum grease was used to seal the wound around the psychrometer to prevent desiccation, Polyurethane foam was then used to secure the psychrometers in place and to insulate them against fluctuations in the ambient environment, The psychrometers were located in the trees to avoid exposure to direct sunlight, Spanner thermocouple psychrometers were also used to determine the soil water potential of each site, Three replications of psychrometers were installed at six depths of about 15, 30, ^5, 60, 120, and 180 cm on each site. The soil water content (%) was determined gravimetrically from three samples in an effort to correlate percent soil water with soil water potential on each site. The gravi- metric samples were taken in about 15 cm increments from the surface to a depth of about 60 cm. Soil water potentials were also determined at depths of about 120 and 180 cm from three replications on each site. 13
'V psychrometer cable
Teflon cup reference junctlons
senslng junctions
screen (optional)
Fig, 1,—Diagram of a double-junction Spanner thermoc'ouple psychrometer used in the study of soil-plant water relationships of honey mesquite. 14
Fig. 2,—Installation of thermocouple psychrometers at three different positions in each tree for plant water potential determinations on the irrigated and non-irrigated site of the study of soil-plant water relationships of honey mesquite. 15
Measurement of the water potential with thermocouple psychrometers were obtained using a Kiethly microvolt meter modified by S-B Systems to be used with thermocouple psychrometers (Figure 3 and 4). Prior to installation in the soil or in the trees, each thermocouple psychrometer was calibrated against standard solutions of O.lm, 0.5ni, l.Om, and 1.4m KCl at different temperatures (Appendix B).
Water potential measurements were made three to four times throughout the day from June 1, 1972, to August 28, 1972. Simultaneously, transpiration rates were measured with a lambda porometer (Figure 5) which was calibrated according to Brown (Unpublished Data) (Appendix C). Soil temperature, air temperature, relative humidity, wind speed, and tirae of day were recorded at the time of each water potential determination. These data were analyzed using a stepwise multiple regression analysis in an attempt to determine the im- portance of the various environmental factors to the water relationships of honey mesquite. 16
Fig, 3.—Measurement of soil water potential with the Spanner therraocouple psychrometer and the S-B Systems microvolt meter. 17
Fig. 4.—Measurement of plant water potential with the Spanner thermocouple psychrometer and the S-B Systems microvolt meter. 18
Fig. 5.—Diffusion porometer used to measure transpiration rates in honey mesquite. CHAPTER IV RESULTS AND DISCUSSIONS
Soil Water Relationships Honey mesquite trees used in this study were subjected to two soil water regimes. The amount of water available to the trees grown under non-irrigated soil water condi- tions was dependent upon local rainfall. Soil • ater potentials and percent soil water were quite variable. The soil water potential on the irrigated site was main- tained at approximately -1 bar (Figure 6), whereas the daily patterns for percent soil water on the irrigated site was variable (Figure 7). The water potential of the soil on the irrigated site indicated the soil was never flooded to the exclusion of soil air except for a brief period immediately following irrigation. Childers and White (19^2) stated that flooding decreased transpiration rates of apple trees within two days. Since transpiration rates following irrigation were as high as those the day before irrigation, flooding did not seem to be a problem, The soil water content (percent) of the non-irrigated site was highly correlated (r = ,92 to .99) to the water
19 20
\
co
n 05 •H +» C « A. / / '^' O \- I - V
0) cd 1 1
I ] I 1 V / I í a Dates
Fig. 6.—Average soil water potentiais at various depths for the irrigated and non-irrigated site June i through August 28, 1972, in the study of soil-plant water relationships of honey mesquite. 21
sr
F.!-
c: -p e: o o 1 13
!toi-n*:i*Tc A-
\
.^' EF
\ /^ V L lul. .VI. 1 15 i5 Dates
Fig. 7.—Average soil water content at various depths for the irrigated and non-irrigated site June 1 through August 28, 1972, in the study of soil-plant water relation- ships of honey mesquite. 22 potential (bars) of the soil from the surface to 6o cm (Figure 8). These results are similar to those reported by Zahner and Stage (I966). They found a curvilinear relationship in the depletion of soil water with an increase in the soil water tension. Similar analyses were not determined for the irrigated site because the water potential was constant (-1 bar). Soil on the non-irrigated site obtained a low water potential of approximately -18 bars. The results of this study indicated that mesquite trees on this site were not under any physiological stress caused by the low soil water potential. Apparently, permanent wilting for honey mesquite is below this point,
Plant Water Relationships The anticipated water potential gradient was measured within the trees growing under both soil water regimes. Water potential in the trees formed a gradient with decreasing water potential with increasing height (Tables 1 and 2). During times of high rates of transpiration these gradients were rather steep, similar to the results reported by Brown (I966). The trees on the irrigated site were often the ones under the greatest internal stress. The average maximum water stress ( H' plant = -30.9) was obtained in trees growing on the irrigated site. The average maximum water 23
• • ,v
*.r -J.0 -' ) -12.0
^
0) +c»; o o u o +>
• :23 'ji 'ií,. •.>«•)
-io -«.0 -L.,J -Í:,J --••J •-«
• •ai
TJS -Tã *3 o To Water potential (bars)
Fig. 8.—The relationship of soil water potential (bars) to soil water content (%) at four depths on the non-irrigated site in the study of soil-plant water relationships of honey mesquite. 24
Table 1,—Average water potentials of the gradient from the soil through the plant into the atmosphere throughout the day on the irrigated site of the study of soil-plant water relationships of honey mesquite.
-p ^ -683.9 -1049.9 -1339.2 -1226.3 -814.1 d 0) •H u X - -15.6 - 19.ÍI - 30.9 - 18.9 -10.7 W) H oú .a: •H +> c: 0) •»-» o «^2- -W.2 - W.6 12.9 - 13.2 - 5.6
+-• 1 ^Jlã. JÍL2- AL ^ - ?.l ^(0 15 i.a 1.0 1.0 - 1.0 - 1.0 1.0 1.0 - 1.0 - 1.0 >i 30 1.0 H í|S 1.0 1.0 - 1.0 - 1.0 •H 1.0 ^60 1.0 1.0 - 1.0 - 1.0 t3 6 1.0 0) f W) & - 1.0 - 1.1 LO - 1.1 - 1.0
-1.0 - 1.0 - 1.0 - 1.0 - 1.0 180 L- -1.0 EARLY MlD ilOON HlD LATE EVE.MrÆ ftoRMING AFTERNOON APTERf^OON 1700-0900) (090O-IIO3) (IL (M400) (1400-1500) (1600-1800) (lS0C-2Ja Z5
Table 2,—Average water potentials of the gradient from the soil through the plant into the atmosphere throughout the day on the non-irrigated site of the study of soil-plant water relationships of honey mesquite.
w -351.2 -653.9 -1147.9 -1295.4 1379.9 -319.1 Q> •H •O (d fø - 8.1 -15.9 - 19.4 - 12.8 12.3 -Ll.l rH íd B •H ^ +>• s=
o ^ « ftc£2 4.3 - 9.8 - 13.3 8.6 8.5 6.2
+> aJ 1 -1.4 - 7.0 - JO.O - 4.3 - 4.5 - 2.3 . -11.3 - 8.4 - 11.2 - 13.1 - 10.5 -14.9 15 H 30 1 l -10.1 - 7.0 - 8.0 - 10.5 - 9.7 -10.6 •3 ^45 -IL.5 - 8.8 - 10.6 - 12.6 - 9.9 -14.8 - 8.8 n ^60 -8.3 - 6.3 - 8.1 - 8.2 - 9.0
W) £ cd ^ 4.0 4.2 - 4.5 4.2 - 5.5 3.4 ® c^izcf-
-2.8 - 1.9 2.9 - 2.7 - 2.9 18tA- EARLY HlD ItooN HlD UTE EVENING ÍIDRNUÆ rbRNING AFTERNOON APTERrWON (0700-0900) (09001100) (1100-1400) (1400-1600) (1600-lS O) (13QO240Û) 26
stress obtained in the trees growing on the non-irrigated site was -19.^ bars,
Water potential in the trees was quite variable throughout the day and on some days reached values of -30 bars, This variation was correlated with the time of day for all positions in the tree, These relationships were curvilinear reaching a peak about mid-day, Maximum stress occurred about noon (Figure 9) in the trees growing on the non-irrigated site, but it did not occur in the trees growing on the irrigated site until liOO to 2i00 p.m. (Figure 10), Scholander et al, (I965) found diurnal cycles very similar to these,
Very little correlation was detected between soil water potential and plant water potential among the trees growing on the irrigated site, Similar results in field crops were reported by Cary and Wright (1971) and Slatyer (1955)« They reported that evaporation directly influenced plant water potential until a critical water potential in the soil was reached, At this time soil water started exerting some influence on the plant water potential, Water potential at any position in the honey mesquite was influenced most by transpiration rates on both the irrigated and non-irrigated sites, With an increase in height in the trees the influence of transpiration on the water potential of the tree increased, while the influence htrnm'i
-20 h 27
-18
-16
-10 Y --15.97 • 0.85 W-0.17 (x^) R-a&l -E
-U
-3
0.T KD UD ixû m ibû 2-JXl
ftjSITIO. 2
ftsnioN 1 -l
-8 .
-0
!)tX a&lJ '>ifl iXO 120: IsOl -COJ bJj 2J.i3 Time of day
Fig, 9,—Correlation of time of day and water potential at three positions in honey mesquite trees growing under irrigated conditions. 28
ftSITIW )
OHt
ft)srTicH 2
am
-10 RDSITKD 1
-8
-6
/ Y- •*; 12 - 1.8S Cx) - JJTg.* (W) \^^
-H / »• .a
-2
1f,T ÛSD 1130 :-'fi IJD OT Time of day
Fig. 10.—Correlation of time of day and water potential at three positions in honey mesquite trees growing under non-irrigated conditions. 29 of soil water remained relatively constant, Water potential in the soil was not correlated (r = .004) with the water potential within the tree.
Atmospheric Water Relations and Transpiration Atmospheric conditions largely determined the rate of transpiration for most plants. The water potential of the atmosphere is determined from the following formula derived from Raoults Law: - ^ =R T— , ^^Po T~ where ^ = water potential (atm) R = universal gas constant (0,08205 liter - atm mole" degree A" ) T = absolute temperature Vj^ = molar volume of water (liters mole"-'-) Po = vapor pressure of pure water at temperature T P = actual vapor pressure of the atmosphere This can be simplified toi -m (bars) = 10,7 T logio (R T) • where RH = relative humidity, The water potential of the atmosphere had a greater influence on transpiration in the trees growing under irri- gation than on those trees growing on the non-irrigated site, Conversely soil water potential had a greater influence on the trees growing on the non-irrigated site than it had on those trees growing on the irrigated site. 30
This indicated that transpiration in mesquite is most influenced by relative humidity, temperature, and wind speed when soil water is unlimited, But as the soil water becomes iess available, the influence of soil water potential on transpiration rates is greater, If the environmental conditions are known, the transpiration rate for honey mesquite caji be predicted using either percent soil water or soil water potentialt for trees growing under relatively dry soil conditions, Y = 191,98 - 1,62 (Xi) + 3.96 (X2) + 4.28 (X3) - 6.93 (X2|.); R^ = .65 where Xi = relative humidity X2 = percent soil water at six inches Xo = percent soil water at 18 inches X/|, = percent soil water at 24 inches for trees growing under field capacity soil conditions,
Y = 215.26 - 2,30 (X^) + 3.07 (X2); R^ = .7S where Xi = relative humidity X2 = percent soil water at 18 inches or for trees growing on relatively dry soil, Y = 181.4 + 1,48 (Xi) - ,79 (X^) + 2.32 (X3); R^ = ,62 31
where X-^ = relative humidity X2 = soil water potential at 12 inches X3 = soil water potential at 48 inches for trees growing under field capacity soil conditions, Y = 179.47 - 1,72 (Xi) + 2.79 (Xg) - 4.6 (X3); R2 = .68 where
^2, = relative humidity X2 = air temperature X3 = wind speed Similar to water potential in the trees, transpira- tion rates adhered to a very distinct daily pattern which was correlated (r = .78 for the non-irrigated site and r = .73 í*or the irrigated site) with the time of day. The relationship was curvilinear with a low of 20g cm"^ min"^ occurring in the morning when the relative humidity was -2 -1 high and reaching a peak of 200g cm min about liOO to 2i00 p.m. (Figure 11). The average transpiration rate for the period of the study of the trees growing on the irrigated site was 134g 2 1 cm min" , while those growing on the non-irrigated site transpired approximately lOOg cm"*^ min""^. The amount of water transpired per leaf area from the trees growing on the irrigated site was significantly more than that transpired from the trees growing on the non-irrigated N M-IRRirwkTtD SlT 32 125 .
m
75
50 •H B Csl I B o 25 o C&Cû lODO i200 1400 leæ lacû 20CO c: o •H IRRIGATED SITE -p
•H (0
OSB Time of day
Fig, 11,—Relationship of time of day and transpiration rates of trees growing on the irrigated and non-irrigated site in the study of soil-plant water relationships. 33 site, The leaf área of the trees on the irrigated site was substantially greater than the leaf area of the trees growing on the non-irrigated site (Figures 12 and 13). Thiq would greatly -increase the amount of water lost per tree on the irrigated site over those trees growing on the non-irrigated site. 34
Fig, 12,—Honey mesquite trees on the irrigated site showing a large number of leaves per tree.
*^
m •\
Fig, 13,—Honey raesquite trees on the non-irrigated site showing fewer leaves per tree. CHAPTER V SUMMARY AND CONCLUSIONS
Honey mesquite, a noxious invader of Texas rangelands, is often thought to be an extravagant user of water. Hence this study was designed to study the water relationships of honey mesquite in West Texas.
Water relationships of honey mesquite were studied on 10 trees growing on two similar sites on the Texas Tech University Research Farm in Lubbock, Texas. One site was irrigated weekly throughout the growing season so the response of honey mesquite trees could be measured as they were influenced by an adequate supply of water. Likewise, the response of the trees growing under natural environ- mental conditions was determined on the non-irrigáted site. The soil water potential for each site was determined from Spanner thermocouple psychrometers installed at depths from 15 to 180 cm, Thermocouple psychrometers were installed at three positions within five trees on each site for internal plant water potential measurements, Transpiration rates and plant and soil water potentials were measured three to four times during the day throughout the study.
35 36
The results of this study indicated that psychrometry can be used very effectively in studying the soil-plant water relationships in honey mesquite, It is imperative that ample time be spent to adequately calibrate each psychrometer used, The field measurements are only as accurate as the calibrations of the psychrometers.
Percent soil water and soil water potential were very closely correlated in the non-irrigated site. The amount of water available for depletion became less as the water potential decreased. Soil water potential in the non- irrigated site reached -18 bars without causing any visible water stress in the honey mesquite trees. The permanent wilting percentage for honey mesquite apparently is below the classic -15 bars. The anticipated water potential gradient was measured within the trees on both sites, although the trees growing on the irrigated site exhibited more internal water stress than the trees growing on the non-irrigated site. Water potential in the trees was very well correlated with the time of day. The trees growing on the non- irrigated site reached a peak quicker and at a higher value than those growing on the irrigated site. Very little correlation was detected between plant water potential and soil water potential, whereas transpiration and plajit water potential were highly correlated. 37
Atroospheric conditions largely determined the rate of transpiration. Relative humidity, air temperature, and wind speed had a larger influence on transpiration when soil water was unlimited than when soil water was limited. Transpiration rates, like water potential, followed a very distinct daily pattern. The trees growing on the irrigated site transpired more water per leaf area than the trees growing on the non-irrigated site. This study indicated that the amount of soil water lost via honey mesquite depends upon the environment in which it grows. Consequently, the influence of honey mesquite growing on important watersheds in the semi-arid Southwest deserves detailed study. LITERATURE CITED
Beckett, S. H. and C. F. Dunshee. 1932. Water require- ments of cotton on sandy loam soils in southern San Joaquin Valley. Cal. Agr. Exp. Sta. Bull. 537. 39 p. Brown, R. W. 1970. Measurement of water potential with thermocouple psychrometersj construction and application. U. S. Dept. Agr. Forest Service Res, Paper Int-80. 27 p. Campbell, G. S., J. W, Trull, and W, H, Gardner, I968, A welding technique for Peltier Thermocouple Psychrometers, Soil Sci, Soc, Amer, Proc, 321887- 889, Cary, J, W. 1971. Energy levels of water in a community of plants as influenced by soil moisture. Ecology 52:710-715. Cary, J. W. and J. L. Wright. 1971. Response of plant water potential to the irrigated environment of Southern Idaho, Agron, J, 03:691-695, Childers, N, F. and D. G. White. 1942. Influence of submersion of the roots on transpiration, apparent photosynthesis, and respiration of young apple trees. Plant Physiol. 17:603-618, Degarmo, H, R, I966, Water requirement and production of eight desert plant species under four soil moisture levels. Master Thesis, N, Mex, State Univ, Univ, Park, N, Mex, 43 p, Gardner, W, R, I960, Dynamic aspects of water availa- bility to plants, Soil Sci, 89:63-73. Hoffman, G, J. and W, E, Sprinter. I968, Water potential measurements of an intact plant-soil system, Agron, J, 60:408-413,
38 39
Hsieh, J,, G, S, Campbell, and W, R, Gardner, 1971. Psychrometric determination of water potential of desert plants, Northwest Sci, 45:209-212, Kanemasu, E, T. and C, B, Tanner, I969. Stomatal diffusion resistance of snap beans, I, Influence of leaf-water potential, Plant Physiol, 44:1547- 1552. Kozlowski, T, T, 1949, Light and water in relation to growth and competition of Piedmont forest tree species, Ecol, Monogr. 19:207-213, Kramer, P, J, 1949. Plant and soil water relationships, McGraw-Hill, N, Y. 347 p. Kramer, P. J. I962. The role of water in tree growth, p, 171-182. In T. T. Kozlowski., (ed), Tree growth. Ronald Press, N. Y. Kramer, P. J. and T. T. Kozlowski. I960. Physiology of trees. McGraw-Hill, N. Y, 642 p, Lambert, J. R. and J. van Schillgaarde. I965. A method of determining the water potential of intact plants. Soil Sci. 100:1-9. Magness, J. R., E. S, Degman, and J. R. Furr. 1935. Soil moisture and irrigation investigations in eastern apple orchards. U. S. Dept. Agr. Tech. Bull. 491. 36 p. Martin, E. N. 1940. Effect of soil moisture on growth and transpiration in Helianthus annuus. Plant Physiol. 15:449-466. McGinnies, W. G. and J. F. Arnold. 1939. Relative water requirement of Arizona range plants. Ariz. Agr. Exp. Sta. Tech. Bull. 80. 81 p. Parker, K. W. and S. C. Martin. 1952. The mesquite problem on southern Arizona ranges. U. S. Dept. Agr. Cric. 908. 70 p. Phillips, W. S. 1963. Depth of roots in soil. Ecology 44,424-429. 40
Rawlins, S. L,, W. R. Gardner, and F. N. Dalton. I968. In situ measurement of soil and plant leaf water potential. Soil Sci. Soc. Amer. Proc. 32:468-470. Scholander, P. F., J. T. Hammel, E. D. Bradstreet, and E. A. Hemmingsen. 1965. Sap pressure in vascular plants. Science 148:339-346. Shimshi, D. I963. Effect of soil moisture and phenylmercuric acetate upon stomatal aperature, transpiration and photosynthesis. Plant Physiol. 38:713-718. Slatyer, R. D. 1957. The significance of permanent wilting percentage in studies of plant and soil water relations. Bot. Rev. 23:585-636. Slatyer, R. D. 1957. The influence of progressive increases in total soil moisture stress on transpiration, growth, and internal water rela- tionships of plants, Aust. J. Biol. Sci. 10:320- 336. Slatyer, R. 0. 1955. Studies of the water relations of crop plants grown under natural rainfall in Northern Australia. Aust. J. Agr. Res. 6:365-377. Slatyer, R. 0, and W. R. Gardner. I965. The state and movement of water in living organisms. Cambridge Univ. Press, London. 129 p. Slatyer, R. 0. and S. A. Taylor, I96O. Terminology in plant and soil-water relations. Nature 187:922-924. Smith, H. N. and C. A. Rechenthin. 1964. Grassland restoration: I. The Texas Brush Problem. U. S. Dept. Agr. Soil Conserv. Service, Temple, Texas. 33 P. Spanner, D. C. 1951. The peltier effect and its use in the measurement of suction pressure. J. Exp. Bot. 11:145-168. Stanhill, G. 1957. The effect of differences in soil moisture status on plant growth. Soil Sci. 84: 205-214. Taylor, S. A. I965. Measuring soil-water potential, p. 149-157. In Methodology of Plant Eco- Physiology. Montpellier Symp. UNESCO Proc. 41
Veihmeyer, F. J. and A. H. Hendrickson. 1950. Soil moisture in relation to plant growth. Ann. Rev. Plant Physiol. 1:285-304, Wgiring, R, H. and B. D, Cleary. I967. Plant moisture stress: evaluation by pressure bomb. Science 155«1252-1254. Wendt, C. W. 1966. A study of techniques to measure and environmental variables influencing the water relations of mesquite (Prosopis glandulosa var. glandulosa Torr.). Ph.D. Dissertation. Texas A & M Univ., College Station, Texas. 82 p. Wendt, C. W., R. H. Haas, and J. R. Runkles. I968. Influence of selected environmental variables on the transpiration rates of mesquite (Pr jsopis glandulosa var. glandulosa (Torr.) Cockr,). Agron. J. 60:382-384. Wiebe, H. H., R. W. Brown, T. W, Daniel, and E, Campbell, 1970, Water potential measurements in trees, Bio, Science, 20:225-226, Woodhams, D, H, and T, T, Kozlowski, 1954, Effects of soii moisture stress on carbohydrate development and growth in plants, Amer, J, Bot, 41:316-321, Zahner, R, and A, R, Stage, I966, A procedure for calcu- lating daily moisture stress and its utility in regressions of tree growth on weather, Ecology 47:64-74, APPENDIX
A. Modal Description of the Amarillo Fine Sandy Loam Soil Series B. Calibration Instructions for Thermocouple Psychro- meters
C. Calibration Instructions for the Lambda Porometer D. Relationship of Atmospheric Water Potential and Transpiration Rates From Honey Mesquite Trees Growing Under Irrigation E. Relationship of Atmospheric Water Potential and Transpiration Rates From Honey Mesquite Trees Growing Under Non-Irrigation F. Daily Environment, Plant Water Potentials, and Transpiration That Existed on the Irrigated Site of the Study of Mesquite Water Relationships G. Daily Environment, Plant Water Potentials, and Transpiration That Existed on the Non-Irrigated Site of the Study of Mesquite Water Relationships H. Name of Equipment Used and Addresses From Which They Were Obtained
42 43
APPENDIX A: Modal Description of the Amarillo Soil Series
The Amarillo series is of moderately sandy reddish chestnut soils of the Southern High Plains, developed in unconsolidated alluvial and eolian moderately sandy cal- careous sediments, and having reddish B horizons of sandy clay loam to heavy sandy loam, Soil Profile: Amarillo fine sandy loam Al 0-10" Brown (7.5YR 4/3) fine sandy loam; dark brown (7.5YR 3/4) moist; weak fine granular struc- ture; slightly hard; friable few to many fine pores; about neutrai; diffuse boundary. 7 to 14 inches thick. B2 10-25" Reddish brown (5YR 4/4) light sandy clay loam; dark reddish brown (5YR 3/4) moist; compound moderate very coarse prismatic and weak medium subangular blocky structure; very hard; friable; blocky peds partly coated with clay films; many fine axid medium pores; about neutral; gradual boundary. 10 to 25 inches thick. B3 25-42- Yellowish red (5YR 5/6) light sandy loam that is slightly less clayey and more friable than above; weak very coarse prismatic structure; very hard; friable; about neutral, becoming weakly calcareous in lower part; clear boundary. 10 to 40 inches thick.
Cca 42-58" Pink (5YR 7/3) sandy clay loam containing some 40 percent of whitish friable accretions of segregated CaCoo; hard; friable; very strongly calcareous; diffuse boundary. 6 to 24 inches thick. C 58-86"+ Reddish yellow (5YR 6/6) strongly calcareous friable sandy clay loam; strongly calcareous but less chalky or limy than Cca horizon; little altered old alluvial or eolian sediments. 44
APPENDIX B: Calibration Instructions for Thermocouple Psychrometers
1. Seal with epoxy glue all thermocouple psychrometers where lead wires enter the psychrometer chamber. 2. Coat thermocouple psychrometer and about 10 inches of wire with silicone vacuum grease. 3. Use calibration chamber similar to the one illustrated in Figure 14. Aluminum is preferred over teflon because of heat transfer ability. 4. Insert thermocouple psychrometers in opening in the top of calibration chamber and tighten to prevent vapor leak, 5. Cut a piece of filter paper exactly to fit and place it in the bottom of the calibration chamber (Figure 15). 6. Moisten the filter paper with standard molal solution of NaCl or KCl, Make sure there is a drop or two extra in the bottom of the calibration chamber to prevent drying of the filter paper, 7. Quickly screw this into the top part of the calibra- tion chamber until you have a vapor proof seal. Be certain to hold the chamber upright to prevent contamination of the psychrometers. 8. Place calibration chamber, with desired thermocouple psychrometers, into a constant temperature bath at lowest temperature at which they are to be calibrated. 9. Leave them from 1 1/2 to 2 hours and read the^ microvolt output on any microvolt meter modified for use with thermocouple psychrometers. 10. Change the constant temperature bath to the next lowest temperature and read the thermocouple psychrometers again in 1 to 1 1/2 hours. 11. Repeat this procedure until you have read them at as many temperatures as required. ^^5
Fig. 14,—Thermocouple psychrometer calibration chamber.
I Fig. 15.—Thermocouple psychrometer calibration chamber illustrating position of the moistened filter paper. 46
APPENDIX B—Continued
12, The thermocouple psychrometers should be cleaned by the following method after each reading, 1 min in boiling distilled water 10 sec in acetone 15 sec in warm distilled water If psychrometers are especially corroded, clean in ultrasonic cleaner, Always use liquid detergent instead of powdered detergent, 13, The thermocouple psychrometers should then be dried in an oven at 70 C for about 6 hours to remove the moisture from the psychrometer chamber, 14, The readings obtained from the calibration procedure can then be plotted on a graph to give a family of curves for each thermocouple psychrometer. 47
APPENDIX C: Calibration Instructions for the Lambda Porometer
To impose an artificial resistance using saturated filter paper and five pieces of plexiglass tubing (1,0, 2,0, 3.0, 4,0, and 5,0 cm long) of the same diameter as the sensing head:
1, Remove the upper clamp from the sensing head and attach one of the tubes in place using a little vacuum grease, 2, Dry the sensing head thoroughly with the vacuum pump, 3, Place a piece of saturated filter paper (saturated with distilled water) on the upper rim to ohe exten- sion tube, place the upper clamp over that, and hold tightly with a clamp or your hand, 4, As soon as the filter paper is in place and securely clamped, begin timing the shift in microamps from 3 to 6 microamps, 5, Repeat the readings at least 10 times for each tube length, and at 0 cm, drying the sensing head thoroughly after each reading, 6, Do this for a range of temperatures (10, 15t 20, 25, 30, and 40 C) in a growth chamber or in a large water bath with the sensor in a plastic bag, 7, Plot the pathlength vs transit time in seconds (fractions of a minute) for each temperature (Figure 16), 8, Calculate the slope (S) of each line, where: ^2 - ^l S = Xg^ - x^— 9, Find Lo, where L = S At - Lo and L = pathlength, for each temperature. 48
:s o •H Csl • {3 H > ^ O • ^ w Q) CQ U Q> :i O u +» • O +> (d \0 •eH ^ • +> 0) 0) O P
APPENDIX C—Continued
10, Calculate various values of R^ vs transit time for each temperature using the equation: j^ __ __S A t - Lo 'L " D where D_js the^^water vapor diffusivity in air in cm"-^ cm" sec*" , This should be a straight line (Figure 17). 11, Use this graph to find R^ of unknown Ry, All you need is transit time and leaf temperature (Figure 18), 12, To find transpiration (T) use the following equation:
Tm („vg ^„-cm 2 „í„-lmm ^; = Ce -p Ca ^L where Ce = vapor concentration at leaf temperature Ca = vapor concentration at air temperature 50 Water vapor diffusivity (D) cm min o
>> +* •H > •H +> •H 01 {::
u 0) +> 6
+> +>*S •H (d > (D H P^ to 0) ÍH EH «H •H
(^ O (d > •H
(D +> (d Sensivity (S) 0) +j r> r> 51
. Ol
• 0°
+> <
• «> (D
•H • "2 +* +> •H CQ
+>
" «^
*A '^
ed e 0 H (H s o p. ffi •H ons h s •H la t R 1 1 co U) •H Pt, Leaf Resistance (R) min cm -1 52. APPENDIX D: Relationship of Atmospheric Water Potential and Transpiration Rates from Honey Mesquite Trees Growing Under Irrigation lRRi« n) 250 min " ) 200 1 ratio n •H CM P4 1 CQ e 150 U C5 100 - 5C R = 0.77 0 • 1 1 1 1 1 1 1 1 1 -JiB -300 -500 -700 -900 100 -liûO -1500 -1700 -IS O -210Û Atmospheric water potential (bars) 53 APPENDIX E: Relationship of Atmospheric Water Potential and Transpiration Rates from Honey Mesquite Trees Growing Under Non-Irrigation m ibN-IRR'.GATHD 130 H I 120 •H ^ uo CVI I 6 100 Y = 22.71-0.13 (x) -0.00001 (x^) o R = 0.81 CJ 90 c O 80 •H +> cd H 70 •H P4 CQ § 60 u Eri 50 m X -2^0) -2200 -2000 -13 0 -IGOO -1^100 -1200 -1000 -800 -600 -ÍJ O -200 Atmospheric water potential (bars) 5^^ c Xí t- fl> § i — C m C3 vO(»VO.rLrN43VOOLr>00— U (d '"^^''^O-^ O ra Q> o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o 1 1 1 1 ••+H> 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 CQ :3 o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o H o* 00 (d co 1 1 1 1 1 1 1 1 1 ' 1 1 1 1 1 ' 1 1 1 1 ' 1 • 1 1 1 1 1 1 1 1 1 1 •H a> +*S o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o C O -^ CM (D vOCT\vOOLni-..i^co— cr\cOvâr-..cMvO 2 00 cr\j-covo cr\fM.j- LnovOvûr--Lnr.-oo-3-vDco — — CM rMoooooooocr\r~.j u-\OLn-3-oo.í.3-cr\LntMr^vO O. •—•— — — — — rMCM < oe — ^ C UJ )- (/1 vDvOOf^ COvOOLncTivomOOLnLn.:J-f^mvO — t- := cc 1^'^C^S2x'^""'^<^'^f~~o^cxjcr\— or^Lf^o'o < < -u < -3- — cTiOcr\LnvOJ- — r^ooomcorjcM — OLno 3 )- aa r^cr\r^cr\ — COm — Lnj-vOmrM o — C^o — r^j-CMr^ — 00— moomoocMLncMrsioo OL CT\cMomLnr-.j- Ln(7AO0C — unOLnr-rjLn-niJ^ >oO"\ CM J- O .* vO m — — CT\ 00000000000 000000000 • I I I • I I I I I • I I I T3 ommooooo 000 000000000 (D 00 • ••••• • • • I • • • • • I I i •H 000000 o o 000 000000000 +> O -^ CM O. t/1 I I • I • • I I I I I i I I I I • a: i I c oc < o Lu a o i- ^ z oooooooooooooooocooo I g 2 I I • • • • I i I • I I • I • • I I t • • o 00000000000000000000 X H • • i t i t • • I I I I I I • • I • • I Q 00000000000000000000 W i I I i • • • t I I I t t 1 t I I I I t c c l/•l 0 0 00 00 00 .CMCMCMfM— — — — — vOvnvO c 0 •—4.* •—*J J-* -** J-' mmmmcMCMCv'cMCM-T-íJ- «0 0 mmmmfMCMCMcMCM — — — •—*J Ll L> 0 u •— •— tn• o CMCMCMvOvOvOvOvOCr^C^O^O^CMCMfMfMCMJ-J-J- o. a c •— V V 0 ^-3-j- — — — — — CMCJcMCMLnLnLnLnLnoocooo —n. u u —. —. .— ^ ^- — •— ^- m m rn <.n — .— •— — —~ —- •— "~ OJ •—4.J u OJ 41 10 u > 0 CM *— .— — vOvOvOvOvO'— '— — — rr-. mmmmO>0\0\ ) l- •— •— < u ^ \«- — CM rMfMfM 1 I I I I I I I I I I I I I I I I I I • < — — — (MíMCMCMmoooocoooLnLnLnvOvO — J'-S' o mmmoOOOOOOOO'— — — — — CMCMCM t I I 1 I I I I I I I I I I 1 I I I I I r^r^r~aO0O00000O0O0OCO>3O0000000O0O0O0000 56 •o r» — CT\0 — -f J- r—O000_or-.00000-TCMO — 0^oor~-c^mmL.->_cnc0Lno-TLnoOLnr-»cM OcMr-~ooocT>r-ooj-_o — 00-Tmcr\r-.-TLn wi — r-j-mor— CMJ--TO Lno oooocij-â'-T Lnoooo cnmoo Ln -T cr\r—-Too r- — Lnj- r-—r — Lno^rMLnmæoo • • I I I I I I I • I I I I I I T I i I )- < COOOmj" OCOOmJ" APPENDIX H: Name of Equipraent Used and Addresses From Which They Were Obtained Thermocouple Psychrometers EMCO Mr. Alan Stoudinger P. 0. Box 344 Angola, Indiana Voltmeters S-B Systems Specialized Instrumentation 2130 Prairie Glen Manhattan, Kansas Wescor 459 South Main Street Logan, Utah Potometer Lambda Instruments Co, 2933 North 36th Lincoln, Nebraska Wind Gauge Weather Measure Corporation Box 41257 Sacramento, California Sling Psychrometer Weather Measure Corporation Box 41257 Sacramento, California Soil Sampling Tube Soil Moisture Equipment Corp, Box 30025 Santa Barbara, California APPENDIX H—Continued Tin Sample Boxes (4 oz capacity) Forestry Supplier Inc. Box 8327 Jackson, Mississippi Poly Urethane Foam Insta-Foam S, W. Leeco Inc. 6112 Griggs Houston, Texas