852 JOURNAL OF FORKSTRV 



ing but comparatively drought-resistant plants. The bareness of this 

 piece of forest floor was due to lack of moisture, not to lack of light. 

 This was confirmed by moisture tests, which showed that the soil be- 

 yond the crown — soil which had been giving up moisture to a thick 

 herbaceous cover all summer and should consequently be drier than a 

 spot which had given up nothing to vegetation and was not subject to 

 high evaporation — possessed 59 per cent of moisture on the basis of 

 air-dry weight as against 20.5 per cent under the crown of the spruce. 

 On the basis of volume, which gives a better conception of the moisture 

 relations in these light soils, the soil in the open contained 19 per cent 

 of moisture, as compared with 5.7 per cent under the crown. In an- 

 other case, in a spruce forest the moisture under a small opening in the 

 canopy was 20.9 per cent by volume, as compared with 7.3 per cent 

 under a spruce crown. In both of these cases the soil under the crown 

 was powder-dry to the touch, while that beyond the crowns felt moist. 

 It is evident, then, that under the crowns of spruce the soil is often so 

 dry that neither reproduction nor herbaceous vegetation can become 

 established, no matter how much light it receives. 



Reproduction 



Counts of the reproduction of spruce, fir, white pine, and cedar, cor- 

 related with* age, showed that spruce, fir, and white pine become estab- 

 lished only at intervals of several years, while cedar comes in every 

 year. The cause of the failure of spruce and fir to become established 

 every year is apparently not related directly to climatic factors, because 

 the season of 1916 was unusually moist and. favorable, yet practically 

 no seedlings of these two species could be found. Probably, then, the 

 reason for this periodicity in spruce and fir reproduction is to be sought 

 largely in the seed supply. White pine reproduced abundantly in 1916, 

 so that climate cannot be eliminated as a factor ; but since it is equally 

 impossible to eliminate the matter of seed production, the periodicity 

 of white-pine reproduction may be due to both the season and the seed 

 supply. 



In fir there are indications of a periodicity of reproduction which is 

 of considerably more importance than that due to the seed supply. 

 Under many spruce stands which have reached about middle age the 

 fir reproduction is nearly all composed of large seedlings from approxi- 

 mately one to three feet in height ; young seedlings are scarce. In these 

 cases it appears that the fir came in profusely under a set of environ- 

 mental conditions different from the present ones. Just what these 

 conditions were it is impossible to say without further study. One of 



