Article Figures & Data
Figures
- Figure 1
Climatic graphs of mean monthly precipitation and evaporation rates for eight major U.S. cities. The Y axis is in inches of precipitation and evaporation, the X axis is in months.
- Figure 2
Evaporation from the pan compared with transpiration from the four tree species for a sampling of dates.
- Figure 3
The change in the ratio of transpiration to pan evaporation as canopy size increases. All species aregrouped. Standard errors as noted.
Tables
Arnold, 1980 (2) 224 ft3 of soil total for tree 21 to 40 ft. in height (8’ × 8’ × 3½’ depth pit). Bakker, 1983 (3) 2½ ft3 of soil for every î ft2 of CPA. Vrecenak and Herrington, 1984 (46) 5543 ft3 for a 64 ft. diameter tree. Perry, 1985 (35, 36) 27 ft3 of soil for every 1 “ of caliper, later refining this to come up with 600 ft3 total for a 10” caliper tree (20’× 20’× 18” depth pit). Kopinga, 1985 (20) 2500 ft3 of soil total as the optimum volume tor a large tree. Cervelli, 1986 (7) 570 ft3 of soil total (10’× 19’ x 3’ depth). Helliwell, 1986 (17) A rooting volume 1/1 Oth of the canopy volume; a 65’ tree with a 40’ spread will need over 7000 ft3 of soil. Moll and Urban, 1989 (30) 1200 ft3 of soil total (20’ × 20’ × 3’ depth pit) for a tree expected to reach a caliper of over 25 inches. ↵A Crown projection (CP) is defined as the total ground area under the dripline of a canopy. It is easy to measure and frequently used as a way to quantitatively describe the canopy relative to some other measurement of plant growth or development.
1
Calculating Crown Projection Leaf Area Index Evaporation Rate Evaporation Ratio CP = (crown diameier)2 ×.7852
Leaf Area Index Leaf surface area to crown projection3
Evaporation Rate Daily pan evaporation4
Evaporation Ratio Ratio of whole tree waier use to pan evaporation(20)2 ×.785 = 314 ft2 × 4 × 0.0167 × .20 4.19 = CUBIC FEET OF WATER LOST PER DAY (31 gallons) STEP TWO: Determining adequate soil volume: Cubic feet of water lost per day 5
Available water holding capacity of the soil (%)6
Rainfall Frequency (Critical number of days)4.19 + .19 × 10 220 = TOTAL CUBIC FEET OF SOIL VOLUME (~6 cubic meters) STEP THREE: Calculating possible bed or container dimensions: Assuming a dcplh of no more than 3 ft, calculate a surface area to accomodate 220 ft3 of soil. This could be configured roughly in at least two ways, an 8 f u 9 ft × 3 ft or a 4 ft × 18 ft × 3 ft bed. - Table 3 Critical Soil Volumes
Estimated critical soil volumes are presented for a representative range of U.S. cities using the soil volume methodology. The tree used in this example has a crown diameter of 20’ and is about 35’ in height. Calculations were based on the nee having a crown projection of 314 fŕ with an average leaf area index of 4. The growing site is Ithaca, N.Y.
CITY EVAPORATION PAN RATE1Inches per month ONE DAV SOIL VOLUME2(Ft3) RAINFALL FREQUENCY3(Days) TOTAL SOIL VOLUME (Pt3) If AWHC4 of soil Is eilher 15% or 19% Ithaca, NY 6.21” July 28 10 300 220 (.70 ftVft2 CP)5 Seattle, WA 7.00” July 30 20 600 480 (1-5 ft3/ft2 CP) Mobile, AL 7.19” May 32 10 300 250 (.80 ft¼2 CP) Indianapolis, IN 7.13” June 33 15 500 400 (l.2ft’/ft≡CP) Minneapolis, MN 7.88” July 35 10 350 275 (.87 ft¼2 CP) Miami, FL 8.03” July 36 10 350 285 (.91 f^/ft2 CP) Denver, CO 9.80” July 45 15 700 525 (1.7 fp/ft2 CP) Phoenix, AZ 14.83” June 68 80 5400 43J5 (14ft3/ft2CP) ↵1 The highest mean mean monthly pen evaporation value for 20-30 years or data record for each city.
↵2 Assumes a soil available water holding capacity of 15%.
↵3 Defines the critical rainfall event A minimum of 92% of all dry periods (less than 1/10’ rainfall) lasted this num ter of days or fewer for etch dty. Derived ton 10 yean of data recced for each city.
4 WHC-available water holding capatity of the nil. This represents du faction of the total water, on a volume basis, thM it actually available (tx toot uptake. Two available water holding capacities are presented for comparison here, an average, 15% and a high. 19%. AWHC of any soil per can be ascertained tn a lab lest, and specified for use a the tree piL
5 Derived cubic feet of soil per square foot of crown projection.
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