The alpine vegetation ecology and remote sensing of Teresa Island, British Columbia

• Main Author: Buttrick, Steven Colby
• Format: Text
• Language: English
• Published: The University of British Columbia 1978
• Subjects: Yukon; Atlin; Bear Mountain; Teresa Island; Grizzly Bear Mountain; Cassiope tetragona; Empetrum nigrum; Salix polaris; Sibbaldia procumbens; Alaska
• Online Access: https://dx.doi.org/10.14288/1.0094758; https://doi.library.ubc.ca/10.14288/1.0094758

The alpine zone, encompassing a considerable portion of the land surface of British Columbia, is one of our major natural resources providing extensive areas for recreation, mineral resources, and needed habitat for many wildlife species including caribou, grizzly bear, mountain goat and mountain sheep. Such an extensive and important natural resource warrants careful research to provide a solid base for proper management and planning decisions. The aims of this study are: 1) To define and describe the vegetation units of an alpine area in northwestern British Columbia; 2) To relate these units to the major environmental factors acting in the alpine zone; 3) To further refine a currently used hierarchical classification suitable for the multi-scale cartographic representation of alpine and forest vegetation; 4) To show the value of remotely sensed data for multi-scale vegetation mapping; and 5) To produce multi-scale maps of the alpine study area, suitable for the requirements of today's land planners and managers. The alpine zone of Teresa Island, within Atlin Provincial Park, was chosen as the study area for its accessibility and representativeness. One hundred fifty-one sites, selected on the basis of species homogeneity, uniform appearance and uniform ecological conditions, were sampled during the summers of 1974, 1975 and 1976. On the basis of dominant species, physiognomic similarity and similar environmental conditions, sixteen community types are described: 1) Umbilicaria blockfield; 2) Cetraria nivalis - Vaccinium uliginosum fell field; 3) Cetraria nivalis - Carex microchaeta fell field; 4) Carex microchaeta meadow; 5) Festuca altaica -Potentilla diversifolia rich meadow; 6) Festuca altaica - Cladina dry meadow; 7) Betula glandulosa - Cetraria cucullata shrubfield; 8) Cassiope tetragona - Cladina mitis heath; 9) Cassiope stelleriana - Phyllodoce empetriformis snowbed; 10) Sibbaldia procumbens - Polytrichum piliferum snowbed; 11) Anthelia juratzkana - Luzula arcuata snowbed; 12) Carex pyrenaica -Luetkea pectinata - Juncus drummondii snowbed; 13) Salix pianifolia -Empetrum nigrum - Sphagnum runoff; 14) Calamagrostis canadensis - PIagiomnium rostratum runoff; 15) Aulacomnium palustre - Salix polaris - Claytonia sarmentosa - Carex microchaeta runoff; and 16) Ranunculus - Carex podocarpa -Saxifraga nelsoniana - moss runoff. Observations and the results of four transects indicate that the local distribution of these communities is primarily controlled by topography, snow duration and moisture. Four habitat types are recognized as a result of major combinations of these factors. These are: 1) Fell fields and blockfields, which occur on the most exposed areas of the mountain where snow is blown off during the winter, and the vegetation is exposed to severe winds and temperatures and xeric conditions year-round; 2) Snowbeds, which protect vegetation from extreme winter temperatures but, at the same time, restrict species occurrence by reducing the length of the growing season; 3) Runoff sites, which include spring-lines, stream edges, pond margins, bog-like areas and other water-saturated sites; and 4) Meadows and shrub-fields which encompass the mesic areas of the mountain where drainage is good and snow cover moderate. The sixteen community types are distributed within the four habitat types and reflect the environmental variation within each. The communities, all of which appear to be in equilibrium with their environment, are compared with other alpine communities described from British Columbia, southern Yukon and southeastern Alaska. Remote sensing is. a valuable tool for the cartographic representation of plant communities. An ecologically based hierarchical classification and legend system, designed to be used with remote sensing data, was expanded to incorporate the alpine communities of Teresa Island. Using satellite imagery, black-and-white, color, and color-infrared photographs, the alpine zone of Teresa Island was mapped at four scales: 1:180,000; 1:80,000; 1:29,000; and large-scale (greater than 1:20,000). The hierarchical ecological classification system was shown to be effective at all scales, and to incorporate all features visible on the image. The hierarchical nature of the system allows maps to be as general or as detailed as information and scale allow without changing the logic of the classification. Color-infrared transparencies are superior to conventional black-and-white and color photos for distinguishing vegetation types. The range of magenta tones associated with foliage is greater than the normally dark shades of green, therefore, changes in the vegetation are more easily detected. Conifers can readily be distinguished from hardwoods. Infrared film is capable of detecting isolated patches of vegetation that tend to blend into the background in black-and-white and color films. Small-scale satellite imagery is valuable for generalized mapping of large areas, and is able to detect the biogeoclimatic zones occurring in northwestern British Columbia. It is concluded that the description, classification and mapping of alpine vegetation in British Columbia is feasible and should be carried out as a prerequisite for any land management program so that we may obtain the maximum and lasting benefit of our alpine resources.