1154 
Journal of Agricultural Research 
Vol. XXVIII, No. 11 
In the fall of 1920 a second test was made by sowing on three different surfaces 
ashes, duff, and bare loose soil. At this time two more species (western larch and 
Engelmann spruce) were added which were also sown on bare soil, ashes, and 
duff surfaces. Separate beds 4 feet square were used for the pine and long beds 
with three divisions of surface within one bed for spruce and larch. Germination 
and survival counts were continued for two years, giving the following results: 
Table IV.— Germination and survival on different surfaces , by species 
(Sowing of 2,000 seed per plot in the fall of 1920) 
Surfaces 
Western white pine 
Western larch 
Engelmann spruce 
Total 
germi¬ 
nation 
Survival 
of germi¬ 
nation 
Total 
germi¬ 
nation 
Survival 
of germi¬ 
nation 
Total 
germi¬ 
nation 
Survival 
of germi¬ 
nation 
Ashes__ 
Per cent 
24.1 
1.6 
24.5 
Per cent 
94.0 
58.0 
o 13.0 
Per cent 
20.0 
4.3 
13.4 
Per cent 
36.0 
35.0 
64.0 
Per cent 
24.0 
14.0 
35.0 
Per cent 
64.0 
0.0 
67.0 
Duff.. 
Bare soil.. 
<* Seedlings were affected by a fungous disease. 
FLUCTUATIONS IN MOISTURE AND TEMPERATURE OF DUFF 
COMPARED TO BARE SOIL 
Moisture fluctuations in duff are seasonal, periodic, and diurnal. The seasonal 
fluctuation is expressed by a gradual loss which progresses with the advance of 
the summer toward a minimum reached early in July. The periodic fluctuation 
involves a drop after each rainfall in summer with a minimum moisture content 
of 10 per cent or lower within 8 to 10 days after the rain, depending upon the 
amount of rain and the drying conditions (fig. 3). There is also a diurnal 
fluctuation which reaches the maximum in early morning and the minimum in 
late afternoon. Tests for 19 consecutive clear days during 1923 showed minima 
at 5 p. m. from 10 to 14 per cent, and maxima at 8 a. m. from 20 to 24 per cent. 
Table V. —Temperature fluctuations in duff and on bare soil 
(Average of daily thermograph records in degrees Fahrenheit June 1 to 30,1921) 
Type of soil 
A. M. 
P. M. 
2 
4 
i 
6 
8 
10 
12 
2 
4 
6 
8 
10 
12 
Duff.—. 
Bare soil... 
55.8 
51.4 
54.9 
50.1 
53.5 
50.4 
54.3 
53.8 
56.8 
60.9 
61.2 
63.1 
66.1 
70.3 
65.0 
65.5 
63.3 
62.1 
61.1 
58.4 
58.8 
55.3 
56.8 
53.2 
Naturally, the duff dries out to a greater depth than ash or bare soil surfaces 
so that seedlings with short and tender roots, like spruce, hemlock and cedar f 
are often overtaken by drought before the roots become properly established in 
the underlying soil. In soil and ash surfaces saturation may be as great as in 
duff but drying out is much less rapid. In this case the entire underlying soil 
must become dry before surface moisture gives out. Again, moisture adheres 
closely to the seeds when sowed in ashes or on soil, in that these become imbedded 
in, or coated with, soil or ashes and are at all times in close contact with the 
surface. From the standpoint of moisture, therefore, soil and ash surfaces 
present more favorable seed beds than duff or loose litter. 
