Arctic LTER: Climate Change and Changing Disturbance Regimes in Arctic Landscapes

该奖项支持位于AK州图里克湖的长期生态研究基地（ARC LTER）的第五阶段。在过去的30年里，北极地区已经明显变暖，北极的土地和淡水已经在发生变化。这些变化包括北极景观的普遍“绿化”，物种分布和丰度的变化，以及局部和区域尺度上地球物理和生物地球化学过程和循环的变化。自1975年以来，ARC LTER项目及其前身通过长期监测冻土带和淡水生态系统与气候变化的关系，通过对整个冻土带、湖泊和河流生态系统的实验操作，以及对阿拉斯加北部和整个北极地区气候不同地点的比较，研究了这些变化。然而，越来越明显的是，北极的气候变暖伴随着扰动状态的剧烈变化，包括与永久冻土融化、野火的惊人增加以及生态系统过程的季节性和同步性变化有关的扰动。这些扰动，除了对生物地球化学、人口和社区产生重大影响外，还导致地表能量平衡、地表温度、水平衡以及冻土带、湖泊和溪流下永久冻土的热量传递发生重大变化。结果是生物群和元素循环的变化比仅对变暖作出反应所预测的要剧烈和迅速得多。从长期来看，与气候变暖相关的扰动变化可能比气候变暖对北极冻土带和淡水生态系统以及整个北极的直接影响更为重要。在接下来的六年里，ARC LTER项目将在一个综合景观框架中解决这些问题，将北极景观视为一个包括苔原、河流和湖泊在内的空间联系系统，并对山坡、流域和区域尺度的变化进行长期预测。长期目标是对包括苔原、河流、湖泊及其相互作用在内的阿拉斯加北部景观进行预测性理解，这一目标保持不变，但未来六年的努力将包括新的重点放在不断变化的干扰制度及其与气候变化的相互作用上。这种重新聚焦将涉及一些努力的转变，从操纵个别气候、生物和生物地球化学驱动因素的长期实验，转向增加对热岩溶、火灾和季节性变化等干扰特征的研究，以及对景观联系和物理干扰的新研究。新的研究领域将包括地表能量交换和进入永久冻土的热通量的变化，以及一个关于气候变化影响和阿拉斯加当地土著社区反应的项目。这项研究的科学影响远不止于提高预测阿拉斯加北部生态系统结构、功能和变化的能力。干扰在长期变化中的作用在生态学中具有广泛的理论和实证意义，并且与对种群、社区、生态系统和复杂景观的恢复力、临界点和阈值的控制密切相关。阿拉斯加图里克湖附近的景观是一个很好的模型系统，可以在多个时空尺度上分析这些问题。图里克湖的工作将提供一个多维视角，了解冻土带和淡水生态系统对环境变化的反应如何对驱动变化的因素产生积极和消极的反馈。这在理论上和从全球气候变化的角度来看都具有广泛的重要性。一个多方面的教育项目将包括：在阿拉斯加巴罗（Barrow）的一个以阿拉斯加原住民为主的小镇上开展一个由讲座和探究组成的校园项目；为记者提供北极生态学和极地科学实地课程；以及本科生和研究生的研究和学位课程。ARC LTER的研究将作为一个景观案例研究造福社会，在这些景观中，当地的生存土地利用仍然普遍和重要，气候变化及其影响直接影响到关键生态系统服务的提供。

This award supports the fifth phase of the Long Term Ecological Research Site (ARC LTER) at Toolik Lake, AK. The arctic region has warmed significantly over the past 30 years and arctic lands and freshwaters are already changing in response. The changes include a general "greening" of the arctic landscape, changes in species distributions and abundance, and changes in geophysical and biogeochemical processes and cycles at local and regional scales. Since 1975, the ARC LTER project and its predecessors have studied these changes by long-term monitoring of tundra and freshwater ecosystems in relation to climate change, by experimental manipulations of whole tundra, lake, and stream ecosystems, and by comparisons among climatically different sites in northern Alaska and throughout the Arctic. Increasingly, however, it is apparent that climatic warming in the Arctic is accompanied by dramatic changes in disturbance regime, including disturbances related to thawing of permafrost, a surprising increase in wildfire, and changes in the seasonality and synchrony of ecosystem processes. These disturbances, in addition to having major impacts on biogeochemistry, populations, and communities, also lead to major changes in surface energy balance, surface temperatures, water balance, and heat transfer into the permafrost that lies beneath the tundra, lakes, and streams. The result is much more dramatic and rapid change in biota and element cycles than is predicted in response to warming alone. In the long term, warming-related changes in disturbance regime may be more important than the direct effects of warming on arctic tundra and freshwater ecosystems, and on the entire Arctic. Over the next six years the ARC LTER project will address these issues in an integrated landscape framework, viewing the Arctic landscape as a spatially linked system including tundra, streams, and lakes and leading to long-term predictions of change at hillslope, watershed, and regional scales. The long-term goal, to develop a predictive understanding of the landscape of Northern Alaska including tundra, streams, lakes, and their interactions, remains the same but efforts for the next six years will include a new emphasis on changing disturbance regimes and their interactions with climate change. This refocusing will involve some shifts in effort, away from long-term experiments manipulating individual climatic, biotic, and biogeochemical drivers, and toward increased effort on characterizing disturbances including thermokarst, fire, and changing seasonality, and on new research focused on landscape linkages and physical disturbance. New areas of research will include changes in surface energy exchange and heat flux into permafrost, and a program on climate change impacts and responses by local Native Alaskan communities.The scientific impacts of this research are much broader than improvement of the ability to predict ecosystem structure, function, and change in Northern Alaska. The role of disturbance in long-term change is of broad theoretical and empirical interest in ecology and is closely related to controls on resilience, tipping points, and thresholds in populations, communities, ecosystems, and complex landscapes. The landscape near Toolik Lake, Alaska is an excellent model system for analysis of these issues at multiple spatial and temporal scales. Work at Toolik Lake will provide a multidimensional view of how responses of tundra and freshwater ecosystems to environmental change can feed back, both positively and negatively, on the factors driving the change. This is of broad importance both theoretically and from the perspective of global climatic change. A multifaceted education program will include: a Schoolyard project of lectures and inquiry in the largely Native Alaskan town of Barrow, Alaska; field courses in Arctic Ecology and in Polar Science for Journalists; and undergraduate and graduate research and degree programs. Research at the ARC LTER will benefit society as a case study of a landscape where local, subsistence land use is still common and important, and where climate change and its impacts are felt directly in the delivery of key ecosystem services.