84 A Study of the Vegetation of 
the young trees can not endure shade. However, openings of 
greater or lesser extent constantly occur in primeval forests due to 
the dropping out of old trees, to windfalls or to fires. Since 
Larix seedlings can do well in openings where the sunlight enters 
during the middle of the day, the chances for reproduction are 
always present. The tamarack, because of its thick bark, is dis- 
tinctly a fire-resistant tree, often remaining unscathed where 
white pine and white fir are killed. Hence, large tracts of burned 
areas, where the tamarack was abundant, now appear to form 
nearly pure Larix communities. However, an examination of the 
new tree populations, together with comparisons with unburned 
contiguous areas, reveals the true mixed nature of the original 
forest. In such places the white fir is especially prominent. 
Abies grandis is not only more tolerant of shade but is also more 
mesophytic than the larch. I have not infrequently found fir 
seedlings in shade so dense as to exclude all other trees except 
the cedar. White fir seedlings can grow in light as low as 0.02 
to 0.015. Under such conditions, however, growth is poor. While 
it can develop in open places in rather dry soil, it is more exacting 
in soil moisture requirements than either Douglas fir or Larix. 
The position of Abies in the normal succession is beautifully 
illustrated on sheltered slopes of outlying mountain spurs and 
buttes. Passing from the dry open pine forest one can find all 
stages from pine-Douglas fir mixture dominated first by the pine, 
to a pine-fir-tamarack mictium where the tall, spindly, bushy- 
topped pines, many of which are dead, tell the story of the lost 
struggle for light. Areas of higher water content on the same 
slope may show Pseudotsuga-Larix mixtures with the fir losing its 
dominance and Abies grandis appearing. The next stage is that 
of a Larix-Abies mictium with the coming in of cedar. Charac- 
teristic plants of these drier Larix-Abies forests are given in the 
following lists: 
Ceanothus sanguineus Ribes viscosissimum 
Holodiscus discolor Rosa gymnocarpa 
Opulaster pauciflorus Rubus parviflorus 
Pachistima myrsinites Salix scouleriana 
84 
