8 BULLETIN 426, V. S. DEPARTMENT OF AGRICULTTJEE. 



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 

 vnih 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 v/here a further addi- 

 tion of light would do harm by decreasing 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 where sugar pine is most flourishing. 

 In the following list the trees are ranked in the order of their ability 

 to endure shade: 



Western yew Taxus brevifolia. 



California nutmeg Tumion calif ornicum. 



Mountain or black hemlock .. . Tsuga meiiensiana. 



Incense cedar Libocednis decvrrens. 



White fir Abies concolor. 



Sugar PiNB Pinus lambertiana. 



Red fir Ahies magnifica. 



Douglas fir Pseudotsuga taxifolia. 



Western white pine Pinus monticola. 



Jeffrey pine Pinus jejfreyi. 



Western yellow pine. Pinus jwnderosa. 



Juniper Juniperus calif ornica. 



Lodgepole pine Pinus contoria. 



Knobcone pine ' Pinus aitenuata. 



Digger pine Pinus sabiniana. 



REPRODUCTION. 



Except under the very best soil, moisture, and shade conditions, 

 there is a noticeable scarcity of sugar-pine 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. 



