Vegetation Succession in the Copper River Basin

• Main Author: Wendy Trowbridge
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: glaciers; Ice; permafrost; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.560.9856

The land surface of the Copper River watershed is undergoing constant change. Every year some new land is exposed and some previously vegetated land is covered by ice, eroded by the river, or burned by wildfire. This regular reworking of the landscape creates a diverse assemblage of plant communities. The process of succession is always being reset somewhere in the watershed. As a result the vegetation is a mosaic of different successional stages set within a matrix of climax spruce forest. The major types of disturbance in the Copper River Basin include: insect infestation, fire, windstorms, fluvial processes, glaciers, deltaic processes, and herbivory. All of these processes are taking place within the larger context of tectonic uplift of the mountains and more recently global climate change. The purpose of this paper is to describe these physical and ecological disturbance processes and how the vegetation community of the Copper River basin responds to them. The Copper River starts in the interior of Alaska, cuts through the Chugach Mountains and spreads out into a large delta as it enters the ocean. The upper watershed is sheltered from the maritime influences and as a result is drier and colder. During the Pleistocene a large lake covered this region. Sediments deposited in this lake created a comparatively flat, poorly drained plateau. In the intervening 12,000 years glaciers have advanced and retreated from the plateau leaving behind a series of moraine deposits. The old lake deposits are now dominated by black spruce forest, and the drier, better-drained moraines are dominated by white spruce forest (Clark and Kautz 1998). Slope aspect and the depth of the active layer above the permafrost, which covers 75 to 80 percent of the area, control dominant forest type through out the interior of Alaska. Only floodplains and south facing slopes are free of permafrost (Viereck et al. 1986). MATRIX SPRUCE FOREST There are three species of spruce that form the matrix or climax forest in the Copper River basin. ...