The northern Alaskan landscape includes a diverse mosaic of ecosystem types that differ greatly in their vegetation, their soils, and their element cycling patterns. This investigation will evaluate some of the important controls and implications of this biogeochemical diversity, using a toposequence of six contrasting ecosystems in the Sagavanirktok River valley as the study site. The first major goal of the project is to describe how individual ecosystems vary in their contributions to the overall patterns of storage and turnover of nitrogen, phosphorus and organic matter in the Arctic landscape as a whole. The approach to this goal is budget-oriented, using a conceptual model of N and P cycling along a toposequence to help compare and contrast the relative importance of major processes in different ecosystems, and to sum up over the whole toposequence. Particular emphasis is placed on the importance of element outputs from one ecosystem to the productivity and nutrient dynamics of its neighbors. The second goal is to understand how the biogeochemical effects of disturbance are propagated, both within a single ecosystem type and along a heterogeneous toposequence. A series of field and laboratory experiments will be combined with simulation modeling and tracer studies. Substantial progress has been made toward resolution of major questions in terms of acquisition of data. As a next logical phase the project group will maintain experiments already in place while concentrating on producing major first-order publications. The work is important because the Alaskan Arctic is under heavy development pressure, yet the long-term and cumulative impacts of this development are not well understood. Most research so far has focused on single ecosystem types that occupy large areas but are not necessarily representative of the range of biogeochemical diversity on the North Slope, or of the ecosystem types most frequently disturbed. Although it is known that disturbance effects spread slowly over the Arctic landscape, very little is known about factors controlling their rate of spread and ultimate extent. This research will result in increased understanding of controls on rate of spread of disturbance in single tundra ecosystems and the overall tundra landscape.
