Biogeochemical Diversity in the Arctic Landscape: Element Transport and the Spread of Disturbance Effects

阿拉斯加北部的景观包括各种各样的生态系统类型，它们的植被、土壤和元素循环模式都有很大的不同。这项调查将使用Sagavanirktok河谷六个不同生态系统的地形序列作为研究地点，评估这种生物地球化学多样性的一些重要控制因素和影响。该项目的第一个主要目标是描述各个生态系统对整个北极地貌中氮、磷和有机物质的储存和周转的总体模式的贡献有何不同。实现这一目标的方法是以预算为导向的，使用N和P沿地形序列循环的概念模型，以帮助比较和对比不同生态系统中主要过程的相对重要性，并总结整个地形序列。特别强调了一个生态系统的元素输出对其邻近生态系统的生产力和营养动态的重要性。第二个目标是了解干扰的生物地球化学效应是如何在单一生态系统类型内和沿着不同的地形序列传播的。一系列现场和实验室实验将与模拟建模和示踪剂研究相结合。在解决数据获取方面的主要问题方面取得了实质性进展。作为下一个合乎逻辑的阶段，项目组将维持已有的实验，同时集中精力制作主要的第一批出版物。这项工作之所以重要，是因为阿拉斯加北极地区面临着沉重的发展压力，但这种发展的长期和累积影响还没有得到很好的了解。到目前为止，大多数研究集中于占据大片区域的单一生态系统类型，但不一定代表北坡生物地球化学多样性的范围，或最常受到干扰的生态系统类型。虽然众所周知，干扰效应在北极地貌上缓慢传播，但对控制其传播速度和最终程度的因素知之甚少。这项研究将增进对单一冻土带生态系统和整个冻土带地貌中干扰扩散速度控制的了解。

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.