Collaborative Research: Aboveground and Belowground Community Responses to Climate Changes in Arctic Tundra

虽然现有的观察表明，北极植物群落在物种组成，净初级生产力（NPP）和生物量方面发生了巨大的变化，以应对气候变暖和随后的土壤养分矿化增加，但目前用于预测北极苔原碳（C）和氮（N）循环的模型缺乏更高的营养水平，因此，缺少可能产生相当大影响的机制。 提供资金，同时测量植物，土壤无脊椎动物和微生物（生物量和多样性），因为它们对土壤养分增加作出反应，以测试有关这种变化的生态理论，并了解营养水平之间的反馈。 这项工作提出了我们是否正在目睹生态系统组成部分的简单增加和微妙变化，或者生态系统中有可能改变当前生物群，碳和氮平衡的根本变化。理论表明，当NPP增加时，额外的营养水平应该进入系统，因为现在有足够的能量来维持它们。 在NPP较低的系统中，如北极苔原，这些变化将更加剧烈，因为动态不是线性的。 该研究将研究土壤群落和养分循环如何对植物生长的变化做出反应，以及这些反应如何在NPP不同的两种常见北极生态系统之间进行比较，干燥的健康和潮湿的酸性草丛苔原。 它将利用阿拉斯加图里克湖现有的北极长距离接触试验区，在长期养分富集的情况下，在试验区规模上检验这些假设，并将建立新的小规模养分修正试验，在这些试验中，将进行更本地化和更频繁的植物和土壤取样，以获得更适合土壤生物的时间和空间尺度。 将使用理论模型和基于数学的模型来帮助分析和解释。

While existing observations suggest that arctic plant communities undergo dramatic changes in species composition, net primary productivity (NPP), and biomass in response to climate warming and subsequent increased soil nutrient mineralization, current models used to predict carbon (C) and nitrogen (N) cycling in arctic tundra are lacking inclusion of higher trophic levels and, thus, are missing mechanisms that may be having considerable effects. Funds are proided to concurrently measure plants, soil invertebrates and microbes (biomass and diversity) as they respond to increased soil nutrients to test ecological theory regarding such changes and understand feedbacks among trophic levels. The proposed work addresses whether we are witnessing simpleincreases and subtle shifts in the ecosystem components or fundamental changes in the ecosystem that have the potential to alter the current balance of biota, carbon and nitrogen.Theory suggests that when NPP increases, additional trophic levels should enter the system because there is now enough energy to sustain them. These changes will be more dramatic in lower NPP systems, such as arctic tundra, because the dynamics are not linear. The study will examine how soil communities and nutrient cycling respond to changes in plant growth and how these responses compare between two common arctic ecosystems that differ in NPP, dry heath and moist acidic tussock tundra. It will use existing experimental plots of the Arctic LTER at Toolik Lake, Alaska to test these hypotheses at the plot scale under long-term nutrient enrichment and will establish new smaller-scale nutrient amendment experiments on which more localized and frequent plant and soil sampling will occur to capture a temporal and spatial scale more appropriate for soil organisms. Theoretical and empirically-based models will be used to aid in the analysis and interpretation.