SPRUCE AND BALSAM FIR TREES. 37 



White fir is very tolerant of shade throughout its life, but it en- 

 dures more shade from the seedling to the pole stage than at any 

 other period. Such growths survive long suppression under heavy 

 shade, but with slow progress, and recover readily when overhead 

 light is admitted. White fir appears to be most tolerant of shade in 

 moist soil, where usually it is able to endure more than any associated 

 species except Engelmann spruce and alpine fir. Owing to its great 

 tolerance, white fir has a closely branched crown, and the trunks lose 

 their branches rather slowly. 



White fir is a fairly prolific seeder, producing large crops of cones 

 periodically. Good seed years occur only at irregular intervals of 

 from two to four years, but some seed is produced nearly every year. 

 As a rule, seed production begins mostly at a rather advanced age, 

 but pole-size trees in dense stands may bear seed when their leaders 

 reach full light. Seed bearing continues for many years, but it is 

 more abundant during the period of rapid height growth (between 

 the ages of 50 and 100 years) than at maturity. The seed has only a 

 moderately high rate of germination (often under 40 per cent) and 

 transient vitality. Reproduction is usually abundant, large dense 

 groups of seedlings often resulting from a single tree's heavy seed 

 crop. 



The character of the seed bed is apparently of little importance, 

 for seed germinates on moist, heavy litter and humus as well as in 

 mineral soil. However, fairly abundant soil moisture is essential 

 during the first few months following germination in order that the 

 seedlings may become established. Indifference to the kind of seed 

 bed renders this tree more than ordinarily agressive, reproduction 

 occurring over denuded lands adjacent to seed trees as well as imme- 

 diately under their own shade. 



Large quantities of seed of this fir are eaten by squirrels 1 and 

 probably also by other rodents which doubtless avail themselves of 



1 The remarkable sagacity of pine squirrels is shown by an incident observed by the 

 writer in connection with their " cutting " of white fir cones in the Manzano National 

 Forest, N. Mex. Part of the cones " cut " from a tree had necessarily fallen directly into 

 a shallow pool of spring water beneath the tree, and it is equally certain that part of 

 them fell on tbe border of the pool. The latter supply of cones had, however, evidently 

 been dragged to the abrupt edge of the pool and pushed into the water. Altogether a 

 bushel or more of cones were thus cached in the water. Evidence that the squirrels had 

 deposited part of the cones in the water appeared in the fact that cones were especially 

 numerous in the water at the edge of the pool. None were to-be found anywhere on the 

 ground about the pool. While the squirrels were not actually seen at work, the position 

 of the tree with reference to the pool was such that only a part of the cones " cut down " 

 could have fallen directly into the water, while the remainder clearly must have reached 

 the ground. The writer was informed by a settler's lad who frequently passed the pool 

 that he had seen the squirrels dragging cones to the water's edge. The effect of placing 

 ripe fir cones in water is to prevent them from breaking up and liberating their seeds, 

 which occurs when the cones are left on the ground exposed to the air. While it is 

 believable that the placing of these cones in the water may have been in accordance with 

 the instinct of squirrels and many other rodents to cache their winter supply of food, it 

 eeems quite unbelievable that the squirrels could know and profit by the fact that 

 immersing fir cones in water temporarily preserves them intact. 



