Relationships between spatial pattern and environment at the alpine treeline ecotone, Glacier National Park, Montana
Allen TR. 1995. Relationships between spatial pattern and environment at the alpine treeline ecotone, Glacier National Park, Montana. University of North Carolina at Chapel Hill
The alpine treeline ecotone is a major landscape boundary separating subalpine and alpine ecosystems in Glacier National Park, Montana. This project mapped and analyzed spatial patterns of alpine treeline using an integrated geographic information system. Multitemporal Landsat Thematic Mapper satellite data was classified into a detailed ecological characterization of treeline vegetation using a hierarchical digital image classification approach, differentially corrected Global Positioning System training sites, and aerial photointerpretation. Treeline patterns were assessed using spatial pattern metrics in topographically defined hillslopes identified by digital terrain analysis. Cluster analyses showed that spatial patterns of treeline comprised six general types related to the diversity of vegetation types present, the juxtaposition of subalpine and alpine types, the degree of edge complexity, and texture of patches. Canonical correlation analysis related spatial pattern attributes to environmental variation in the treeline ecotone. The hypothesis that environmental gradients explain the most spatial variation of treeline was affirmed. Subordinate factors affecting treeline patterns were snow avalanche path disturbance and the presence of sills, faults, and perennial snowfields. Alpine treeline pattern-environment linkages included: contagion and elevation, edge density and slope angle, forest-tundra juxtaposition and insolation variability, and an association between vegetation class diversity and topographic wetness variation. The research identified areas where treeline patterns are potentially climatically controlled and not restricted by disturbances, topographic controls, or geologic structures.