THE LARCH-PINE FOREST. 



221 



The range in altitude is shown by the following list, in which the order is 

 descending. The first two belong primarily in the subalpine forest. 



Abies lasiocarpa. 

 Picea engelmanni. 

 Pinus contorta. 

 Pseudotsuga mucronata. 



Abies grandis 

 Larix occidentals. 

 Thuja plicata. 



Pinus monticola. 

 Tsuga heterophylla. 

 Pinus ponderosa. 



Weaver (1917: 19) has studied succession in the transition forest near 

 Moscow, Idaho, and has determined its relation to water-content, evaporation, 

 and soil temperature. Thuja is the final dominant in this region, Tsuga being 

 absent. The sequence is as follows : Symphoricarpus-Opulaster, Pinus-Pseudo- 

 tsuga, Pinus, Pseudotsuga, Larix- Abies, Larix, Abies, Thuja (Tsuga). 



The water-content of the yellow pine community ranged from 5 to 15 per 

 cent lower than in the Douglas fir-larch, and 20 to 30 per cent below that in 

 the grand fir-larch, while in the latter it was 10 to 40 per cent lower than in the 

 final cedar forest. Evaporation in the latter was 2 to 5 c.c. less daily than in 

 the Pseudotsuga-Larix mictium and 5 to 15 c.c. less in this than in the yellow 

 pine forest. The soil temperatures decreased with much uniformity from the 

 pine to the cedar community. The minimum light value for the Pseudotsuga 

 forest is about 0.02, for the Larix-Abies mictium 0.01 to 0.007, and for the 

 Thuja forest 0.005 to 0.003. 



SOCIETIES. 



The number of these depends primarily upon the light intensity. In the less 

 shady Larix-Abies forest, the number is fairly large and the shrub layer is 

 well-developed, while the deep shade of the Thuja forest permits but a small 

 number to persist (Weaver, 1917: 86, 88). 



Shrubs: 



Chimaphila umbellata. 

 Lonicera utahensis. 

 Menziesia ferruginea. 

 Pachystigma myrsinites. 



Herbs: 



Actea spicata arguta. 

 Adenocaulum bicolor. 

 Anemone quinquefolia. 

 Arnica cordifolia. 

 Asarum caudatum. 

 Clintonia uniflora. 



Shrubs: 



Ribes lacustre. 

 Herbs: 



Aconitum columbianum. 



Anemone quinquefolia. 



Asarum caudatum. 



Athyrium cyclosorum. 



Circaea pacifica. 



LARIX-ABIES COMMUNITY. 



Pirus sitchensis. 

 Ribes viscosissimum. 

 Ribes lacustre. 

 Rosa pisocarpa. 



Coptis occidentalis. 

 Disporum majus. 

 Fragaria vesca. 

 Linnaea borealis longiflora. 

 Mitella trifida. 

 Pirola picta. 



THUJA COMMUNITY. 



Rubus parvifiorus. 



Claytonia asarifolia. 

 Clintonia uniflora. 

 Coptis occidentalis. 

 Smilacina amplexicaulis. 

 Streptopus majus. 



Rubus parvifiorus. 

 Sambucus melanocarpa. 

 Vaccinium macrophyllum. 



Streptopus majus. 

 Thalictrum occidentale. 

 Tiarella unifoliata. 

 Smilacina amplexicaulis. 

 Trillium ovatum. 

 Washingtonia divaricata. 



Tiarella unifoliata. 

 Trillium ovatum. 

 Viola glabella. 

 Viola orbiculata. 



