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

该奖项支持位于阿拉斯加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，北极地区已经显著变暖，北极的土地和淡水已经在相应地发生变化。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地方和区域尺度的地球物理和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原和淡水生态系统与气候变化的关系，通过对整个冻原、湖泊和溪流生态系统的实验操作，以及通过比较阿拉斯加北方和整个北极地区气候不同的地点，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机制的急剧变化，包括与永久冻土融化有关的扰动，野火的惊人增加，以及生态系统过程的季节性和同步性的变化。这些干扰，除了对地球化学，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，湖泊和溪流下方的永久冻土的热传递发生重大变化。其结果是，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。从长远来看，与变暖有关的扰动机制的变化可能比变暖对北极苔原和淡水生态系统以及整个北极的直接影响更重要。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空间上相互联系的系统，包括苔原、河流和湖泊，并导致对山坡、流域和区域尺度变化的长期预测。长期目标是对北方阿拉斯加的景观，包括苔原、溪流、湖泊及其相互作用，进行预测性了解，这一目标保持不变，但未来六年的努力将包括对不断变化的扰动机制及其与气候变化的相互作用的新的重视。这种重新聚焦将涉及一些努力的转变，远离操纵单个气候，生物和生物地球化学驱动因素的长期实验，并增加对热喀斯特，火灾和季节性变化等干扰的描述，以及专注于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，以及当地阿拉斯加土著社区对气候变化影响和反应的计划。这项研究的科学影响比提高预测北方阿拉斯加生态系统结构、功能和变化的能力要广泛得多。扰动在长期变化中的作用在生态学中具有广泛的理论和经验意义，与种群、群落、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，在多个空间和时间尺度上分析这些问题。在图利克湖的工作将提供一个多层面的观点，冻土带和淡水生态系统对环境变化的反应如何能够反馈，积极和消极的，对驱动变化的因素。这在理论上和从全球气候变化的角度都具有广泛的重要性。一个多方面的教育计划将包括：在阿拉斯加州的巴罗的大部分阿拉斯加原住民城镇进行讲座和调查的校园项目;为记者提供北极生态学和极地科学的实地课程;以及本科生和研究生研究和学位课程。ARC LTER的研究将使社会受益，作为当地生存土地使用仍然普遍和重要的景观案例研究，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.