32 BOTANICAL GAZETTE [JANUARY 
determination or computed from the moisture equivalent mechani- 
cally determined. These data will be found in table II. For 
purpose of comparison similar data from the jack pine, black-oak, 
and the Kalamazoo maple-beech associations are added. 
A study of these data brings out certain facts which are quite in 
agreement with field observations. The range in TFC in the 
Big Pines at 7.5 cm. from 7.1 to 14.9 per cent, with a corresponding 
range in WHC (column 3) from 48.5 to 52.5 per cent, is a direct 
expression of the effect of fires on the humus layer. At 25 cm. this 
effect is less apparent in the WHC, but the absence of protection 
from a good humus layer is shown in the TFC at the same depth. 
TABLE II 
SOIL WATER DETERMINATIONS IN PERCENTAGES 
TFC by DW WHC by DW |WHC by volume] WC by formula 
Station and association 
7.5cm.| 25cm. | 7.5cm.| 25cm. | 7.5cm.] 25 cm. | 7.5 cm.| 25 cm. 
6. Upper Pines. -- 2. <.-. 4.9 |. 6.61 44.4: ((98- 7 154.5 1. 4t.8 bei.2 fe 
4. Upper Pines.......... 0:0 |: S35 [43.4.1 38.2 | $2.3 | 4304 1 10.8 1. Fo 
9. jel she nek ae 7X) 4.3) 96-3 1.40.8 | 48.9 1g POS ee 
go Jack pie us cites 14.7 1. 6.1 | 50.90 |: 34.9] 60.4] 42.7 | 13-01 Tea 
3. Black-white oak...... 6.4 | €:7 |.33-% 190.3 } 48-4 42:7 | 8a re 
teante noch (Kalamazoo) NT, Peis 62.1 | 33.4 | 62.7 | 45.7 | 14.5 | 8-5 
The soil is often so baked that it is grayish and “‘dead”’ to a depth 
of 4 or scm. These oft repeated fires must have had marked 
influence upon growth increment of the facies, as well as largely 
determining the presence or absence and nature of the shrubby, 
herbaceous, and ground layers. The WC (column 4) exhibits in 
another way the same regressive influence due to humus destruc- 
tion, producing a soil condition which must act selectively upon 
the various invading propagules. The uniform WHC and WC at 
25 cm. in the Big Pines, as well as in the jack pines and oak associa- 
tions, are very significant and form the evidence for the conclusion — 
advanced in the former paper that the soil conditions reveal no 
differences of causal magnitude, and are thus clearly inadequate 
to explain present forest distribution, or to give any indication of 3 
a causal successional factor. 
eee aT 
