INFLUENCE OF SNOW PATTERNS AND SNOW AVALANCHES ON THE ALPINE TREELINEECOTONE

Snow avalanches, snow accumulation, and snow ablation patterns were ma pped and analyzed to asses their impact on the three-dimensional posit ion, composition (closed canopy forest, open canopy forest, meadow, kr ummholz, and non-vegetated surfaces), and spatial structure of the Alp ine Treeline Ecotone (ATE) in a portion of Glacier National Park, Mont ana, USA. Multitemporal Landsat Multispectral Scanner data were proces sed to derive snow accumulation and ablation patterns throughout a sno w season. Landsat Thematic Mapper data were processed and combined wit h aerial photo interpretations for discerning and characterizing snow avalanche paths. Transition matrices were used to assess the change in the state of snow cover conditions, whereas multiple regression analy ses were used to examine the position and character of snow avalanche paths. The analyses were framed and implemented within a geographic in formation system (GIS) approach. Results indicate a snowmelt pattern p rogressing from zonal to azonal; influence of local site and situation factors in snow accumulation and ablation patterns; and the importanc e of topography, geologic structure, and lithology in defining the sta rting elevation and source area of snow avalanche paths. Finally, a co nceptual process is presented where sites affected by stresses and dis turbances are analyzed at a local spatial scale for analysis through a deterministic model, whereas regional stresses and disturbances are a ssessed through remote sensing and GIS approaches for analysis through empirical models.