Arctic-Alpine tundra ecosystems of the Arrigetch Creek Valley, central Brooks Range, Alaska
University of Colorado, Boulder
2 Vol.: Illus., Maps
Alaska Resources Library & Information Services: QH541.5 T8 C66
The present study examines the ecosystems and biota in the arctic-alpine zone of the Arrigetch Creek valley in relation to the mountain environment. The relationship to the ecosystems and flora of other related arctic and alpine regions is explored. The Arrigetch Creek valley is a continental, high latitude, relatively low elevation region in the central Brooks Range. It is one of the few places in North America where granite and limestone outcrop adjacent to each other. Four approaches were used in this study. The are the principles of dynamic ecology, Braun-Blanquet floristic-sociological approach to classification, numerical methods of ordination and hierarchical cluster analysis, and floristic-phytogeographical analysis. Also included are discussions of 235 vascular plant taxa, 197 lichens, and 135 bryophytes found in the study area along with investigations of regional climate, geology and soils, and fauna. Five orders, 10 alliances and 49 associations are described according to the Braun-Blanquet system from 459 releves in which 432 taxa occur. Hierarchical dendrograms and ordination support the classification. Associations in which Dryas octopetala ssp. octopetala is a dominant taxa are classified into two orders, 3 alliances and 13 associations. The classification presented here is different from the European and Scandinavian treatment of Dryas communities. Ecosystems show the greatest similarity to other dry and/or continental portions of the Rocky Mountains, Scandinavia, Spitsbergen, Greenland, and Siberia. Winter snow cover in March-April 1981 was of equal depth and duration on all slope aspects and increased slightly with elevation. It was not reworked by wind. Taxa such as Carex rupestris, C. nardina, and Dryas octopetala which are characterized as being chionophobic do not appear to be chionophobic in the study area. These taxa are calciphilous and occur primarily on highly disturbed sites. Kobresia myosuroides dominated ecosystems are rare in the study area. They are limited by downslope soil movement. The presence of Artemisia alaskana dominated ecosystems indicates that vegetation related to "arctic-steppe" occurs in the Brooks Range at the base of warm south-facing slopes.
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