Changing land-atmosphere interactions in Arctic tundra

气候变化正在影响北极广阔而多样的陆地景观。火灾、草食和长期变暖等干扰正在重建植物群落，并改变水、能量和碳在北极冻土带和大气之间流动的数量和时间。这一点尤其令人担忧，因为带有永久冻土的北极土壤是巨大的碳库。拟议的研究解决了一个关键问题——北极苔原正在发生的变化是加速还是减缓了气候变暖？达令湖冻土带生态系统研究站的实地研究将在未来五年内测量四种不同冻土带生态系统和大气之间全年的二氧化碳和甲烷交换。这将使我们第一次能够评估这些生态系统的年度碳汇/源强度以及秋、冬、春碳和水循环的重要性。我们对生长季节通量的长期记录表明，这片苔原是二氧化碳的大量吸收地，尤其是在大片灌木覆盖的情况下，它们正在侵入整个北极的苔原地区。然而，夏季获得的大部分碳很可能会在一年中剩下的几个月里通过分解而损失掉。我们将确定影响这些碳损失的因素，这些碳的年龄，以及在春季融雪使冻土带饱和时，有多少碳以二氧化碳、甲烷和溶解碳的形式离开。最后，我们收集的数据和我们从这项研究中学到的东西将用于继续开发陆地表面模型。该模式被用于加拿大气候模式和地球系统模式家族，这将有助于改进加拿大在国家和区域尺度上的气候预测。

Climate change is impacting the Arctic's vast and varied terrestrial landscape. Disturbances such as fire, herbivory, and long-term warming are restructuring plant communities and changing how much and when water, energy and carbon flows between Arctic tundra and the atmosphere. This is especially concerning as Arctic soils with permafrost are huge reservoirs of carbon. The proposed research addresses the critical question – are the ongoing changes in the Arctic tundra accelerating or mitigating climate warming? Field research at the Daring Lake Tundra Ecosystem Research Station will measure year-round carbon dioxide and methane exchange between four different tundra ecosystems and the atmosphere over the next five years. This will allow us for the first time to evaluate the annual carbon sink/source strength of these ecosystems and the importance of fall, winter and spring carbon and water cycling. Our long record of growing season fluxes shows this tundra is a substantial sink for carbon dioxide, especially with greater shrub cover, which is encroaching onto tundra regions across the Arctic. However, it is likely much of the carbon gained in summer will be lost through decomposition throughout the remaining months of the year. We will identify the factors which influence these losses of carbon, the age of this carbon and how much of it leaves as carbon dioxide, as methane, and as dissolved carbon in spring when snowmelt saturates the tundra. Finally, the data we collect and what we learn with this research will be used to continue to develop a land surface model. This model is used in the family of Canadian Climate Models and Earth System Models, which will help improve Canada's climate projections on both national and regional scales.