1236 
Journal of Agricultural Research 
Vol. XXVIII, No. 12 
other systems of treatment, on account of the small amount of tree growth. 
Thus it is that seedlings that get a start while stored-up moisture is available in 
the spring, and before the aspen activity starts, are furnished with a fairly uniform 
supply of moisture throughout the season and survive. This is in contrast 
particularly to the condition under the original stand, where the multitude of 
seedlings, accustomed at first to plentiful moisture, hence not stimulated to 
deep rooting, easily succumb as this moisture is rapidly exhausted by the roots 
of the older trees. 
The shelterwood area, being protected by the control plot against excessive 
wind movement and evaporation, has practically as plentiful a supply of mois¬ 
ture in the spring as the selection plot with more crowns. This is due also to the 
accumulation of drifted snow in the winter along the west side, and a relatively 
small drain by the old trees, and insures good germination and survival. The 
factor of winter protection, provided by drifting snow and shelter from the con¬ 
trol plot, is, however, a matter of relative position rather than one of the silvi¬ 
cultural systems involved. The prevention of drifting, on the other hand, 
especially on the clear-cut area, is a strong argument in favor of brush scattering. 
But the moisture supply or lack of it, which is the determining factor in the 
success of reproduction, may in turn be determined by density of stand. The 
percentage of seedlings surviving is governed most directly by late summer or 
fall drought, which is most severe where the heaviest stand remains, in spite of 
the fact that the degree of protection of soil and seedlings varies with the density 
of the stand. All other conditions are inconsequential in comparison with the 
drought caused by the drain of the older trees upon the moisture near the surface. 
The seedling’s worst enemy in many cases may be its parent tree. 
The importance of soil moisture in the success of Douglas fir reproduction upon 
these plots was first brought out by F. B. Notestein in 1912. He established 
sixty 10-by-10-foot reproduction plots, regularly scattered over the entire area 
before it was cut, and studied the influence of light intensity, soil moisture at 1,2, 
and 6 inches, organic content of the soil at 1 and 2 inches, and soil temperature 
at 6 inches, upon the character of the reproduction. 
It was determined that Douglas fir will reproduce successfully in a light 
intensity of 8.5 per cent. In a stand having an average light intensity of 27.24 
per cent, reproduction averaged most abundant at points of least light; but 
Notestein was satisfied this simply meant that there was sufficient light every¬ 
where under such a stand, which is comparable to the present control stand, but 
that in the openings where light is intense other conditions were unfavorable. 
Soil moisture was found to decrease with increase of light. At the same time, 
Douglas fir reproduction was greatest at those points having the greatest soil 
moisture. All facts indicated that soil moisture not only is a more potent factor 
than light in controlling reproduction, but that it is the controlling factor. 
The total soil moisture varied directly with the amount of organic matter in 
the soil, while the available soil moisture varied inversely with it. The relation 
between the amount of humus and reproduction is uncertain, but the facts 
brought out indicate the probability that there is a point up to which humus 
increases water capacity more than wilting coefficient, and is, therefore, favor¬ 
able to reproduction, and beyond which it has the reverse effect. 
No relation was found between soil temperature and reproduction. 
SLASH SCATTERING VERSUS SLASH BURNING 
In order to compare the relative values of scattering slash and piling and burn¬ 
ing it, the total Douglas fir, Engelmann spruce, and limber pine seedlings present 
in 1923 following the two methods of slash disposal are shown in Table I. 
