—68 BULLETIN 426, U. S. DEPARTMENT OF AGRICULTURE. 
LIGHT. 
Sugar pine demands a very great amount of light, except in early 
youth, and always just as much light as will not interfere seriously 
with the moisture conditions. The maintaining of the balance be-— 
tween light and moisture offers the hardest problem the forester has 
to solve in his attempts to increase the representation of this species 
in the forest mixture of the future. During the seedling and sapling 
stages, on account of persistent demands for moisture, sugar pine 
must have at least partial shade. As it gets older, however, it © 
demands more and more light up to the point where a further addi- 
tion of light would do harm by ee too much the amount of 
- moisture in the soil and air. 
The relative demands of the different species for light vary, quite 
naturally, according to geographical and altitudinal location. It - 
may be worth while, nevertheless, to show how sugar pine and its ~ 
associates rank in this respect aN SS: sugar pine is most flourishing. 
In the following list the trees are ranked 1 in the order of their ability 
to endure shade: 
Western yew...----.---:--:. Taxus brevifolia. 
California nutmeecs sas. ee Tumion californicum. 
Mountain or black hemlock... T’suga mertensiana. 
Incénse-cedar: :22 20 s2ee Trbocedrus decurrens. 
White fire... .55. 2 Bee Abies concolor. 
DUGAR PINE =. ose ees Pinus lambertiana. 
Redsiirs 250.822 a erates = ake Abies magnifica. 
Douclas firs 2327S ee Pseudotsuga taxifolia, 
Western white pine........-- Pinus monticola. 
Jetrey pines. ee 5) eee Pinus jeffreyt. 
Western yellow pine......-.-- Pinus ponderosa, 
Jumper so os 2 Juniperus californica. 
Boadeepole pie: <2 22k Pinus contoria. 
Kmebeone pine. - 2-22 222522 Pinus attenuata. 
Daseer Pine. <2 .5.0e2 ee eae Pinus sabiniana. 
REPRODUCTION. 
Except under the very best soil, moisture, and shade conditions, 
there is a noticeable scarcity of sugar-pme reproduction in the pres- 
ent forest, even where this species makes up as much as 25 per cent 
of the merchantable stand. This scarcity is attributable to the fol- 
owing causes: ; 
(1) The seed is very conspicuous and edible. Large quantities 
are therefore consumed by birds and rodents. 
(2) The proportion of the seed that germinates is small. 
(3) The moisture requirements for germination are exacting. 
(4) The seedlings are very susceptible to injury from fire, drought, 
or severe sunlight. 
