Apr. 14.1923 Physiological Requirements of Rocky Mountain Trees 123 
Tabi,^ VII .—Actual water losses and transpiration in relation to size and growth in 
ig20 —Continued 
Species. 
Irodgepole pine. 
Engelmann spruce. 
Pot No. 
0 
10 
12 
Transpiration: 
y 
May II to 31. 
64-5 
154.8 
83.7 
246. 6 
94-5 
243. 2 
125.9 
177*3 
0^. < 
00. 6 
J81.8 
•JO*?* ^ 
June.”. 
yo* ^ 
143*3 
yy* 
127 . 0 
July. 
607.1 
923- 6 
708.9 
(6) 
118. 7 
10.1. I 
0 “^ /* / 
607.8 
894-5 
926.0 
(5) 
123.8 
196.3 
394-0 
, , 435 * ^ 
/ (8) 
1 103.1 
548.3 
726. 0 
627.5 
(6) 
106.8 
212.1 
149.4 
240.5 
224.8 
(7) 
42.3 
August. 
341-3 
363-6 
(s) 
56. 2 
272. 5 
227. 8 
September. 
October (to day indicated).. 
(5) 
29.8 
Total for season. 
I; 347 -8 
79.6 
2 > 338.9 
79.0 
2,696. 0 
79-0 
1,276.4 
77 * 7 
893.8 
79*4 
951 - 7 
77 - 7 
306. 6 
77 * 7 
Correction, direct evaporation... 
Net transpiration. 
I, 268. 2 
2. 259. 9 
2,617. 0 
1,198. 7 
814.4 
874-0 
2,983.9 
Transpiration: 
Grams per gram weight ac¬ 
cretion— 
Green. 
148 
204 
195 
138 
162 
140 
140 
Dry. 
A 20 
AQA 
701 
802 
688 
450 
431 
Grams per gram mean green 
weight. 
52-9 
82. 0 
66.9 
74-6 
103. 8 
86.1 
A<» ^ 
Grams per square centi¬ 
meter leaf exposure. 
II. 4 
19. 0 
IS -4 
II. 6 
12. 0 
10.4 
10 . I 
Species. 
Timber pine. 
Bristlecone 
pine. 
Scotch pine. 
Siberian larch. 
All. 
Pot No. 
16 
21 
8 
4 
13 
6 
20 
Transpiration: 
May II to 31. 
131.2 
79- 2 
57.3 
74- 3 
81. 7 
39- I 
71.9 
60. 2 
June. 
151.2 
77. 2 
105.3 
128.1 
149.1 
I2I. 6 
158.1 
vy. ^ 
152.8 
July. 
321.3 
84.1 
128.8 
114- 5 
183.4 
231.0 
216.2 
165.6 
August... 
484.4 
112.9 
132. 2 
107.5 
194.7 
416. 0 
September... 
1 534-4 
125. 2 
108.4 
87.6 
212. 7 
454*7 
123.5 
152.8 
1 . 
October (to day indi- 
/ (8) 
(7) 
(3) 
(3) 
(6) 
(8) 
} . 
CcitcQ/ 
1 132- 5 
31-4 
7-1 
0. 7 
38* 2 
102.1 
Total for season. 
1,755.0 
510. 0 
539- I 
518. 7 
859.8 
1,364. 5 
1,046.7 
862.8 
Correction direct evaporation 
79.6 
79-4 
76. 0 
76.0 
79.0 
79.6 
70.3 
70.3 
Net transpiration. 
i» 67 S *4 
430.6 
463.1 
442. 7 
780.8 
1,284. 9 
976.4 
792. 5 
247,940 
Transpiration: 
Grams per gram weight 
accretion— 
Green. 
170 
230 
168 
420 
191 
243 
311 
198 
Dry. 
773 
4 j 785 
317 
434 
409 
464 
333 
257 
522 
Grams per gram mean 
green weight. 
24*4 
13* S 
IS* I 
32.0 
25.6 
52.6 
94.0 
49.7 
42.4 
Grams per square centi¬ 
meter leaf exposure. 
7*0 
3*6 
3*7 
6.3 
5*0 
II. 9 
10.0 
6.0 
8.81 
On the basis of the growth made, the transpiration is also less in 1920 
than in 1917, though not so strikingly so. For green-weight accretion 
the figures are 198 and 263, and for dry-weight accretion 522 and 880, 
respectively, for 1920 and 1917. In other words, for green-weight accre¬ 
tion it required 75 per cent as much water in 1920 as in 1917, and for 
dry-weight accretion 59 per cent as much. The difference between these 
two percentages and between the two years may be due largely to the 
fact that very little foliage falling in 1917 was salvaged and accounted 
for, while in 1920 this was carefully done. However, it is believed the 
amount dropped by the trees in 1917 was relatively very small and 
insufficient materially to affect the results. 
It seems fairly evident that the transpiration per unit of growth is a 
more stable quantity than that per unit of leaf exposure or whole mass, 
in spite of the fact that the former is very much dependent on the whole 
leaf area functioning. 
