Tree and sagebrush density and its influence on snow accumulation at a the lower forest

Lawson, Ernest
Vegetation feedbacks governing snow accumulation across forest boundaries are inadequately investigated. Some studies have assessed snow dynamics at the cold and wet upper treeline; however, different processes and interactions may be significant at the water-limited lower forest boundary. During 12 weeks, from January to March, I took weekly snow depth and density measurements at 33 points along three 50-m transects across a sagebrush-forest boundary. Additionally, I estimated tree and shrub density. The study area covered an ecotone consisting of big sagebrush and lodgepole pine communities in the Medicine Bow Mtn. During the snow accumulation phase, snow was deeper in the sagebrush than in the forest. Snow depth in the forest was reduced by a high density of trees and by tall trees. Snow density increased with time, but was not affected by vegetation type. Since snow depth was greater, snow water content was higher in the sagebrush than in the forest. Snowmelt started in the sagebrush at the end of February, whereas in the forest it was delayed. Because warmer winter temperatures predicted under climate change will have a large influence on snowpack, it is important to understand the competitive characteristics of vegetation and how these relate to differences in snow accumulation and melt at the lower forest boundary.
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