Permafrost thaw as a framework for understanding plant-microbial interactions and terrestrial feedbacks to climate

加拿大一半的土地位于永久冻土上，这是一层冻土、水和岩石。我们是一个永久冻土国家。加拿大北部也是地球上变暖最快的地区之一，从根本上塑造了整个北部生态系统、基础设施和资源的稳定冻土正在以前所未有的速度融化。融化的永久冻土为微生物提供了新的能源，微生物反过来向大气中释放二氧化碳和甲烷，进一步加剧了温室效应。这种循环被称为“永冻层碳反馈”，是最有可能的陆地对大气变暖的正反馈之一。然而，作为温室气体的多年冻土碳释放的命运取决于几个关键因素，包括1)融化的土壤是否会变得洪水泛滥，这可能会减少微生物的活动；2)永久冻土的融化是否会创造营养丰富的条件，从而刺激微生物的活动；以及3)融化后植物生长的增加是否有助于抵消永久冻土的碳释放。为了解决这些问题，拟议的研究将从机理上理解西北地区和阿拉斯加的植物和微生物在有氧和无氧融化轨迹下是如何争夺养分的，这两个地区的永久冻土正在经历广泛的融化。这项研究将测量随着永久冻土融化，氮和磷有效性的变化，以及土壤养分丰富对植物和微生物过程的影响。实时检查植物和微生物过程的实验研究将得到梯度方法的补充，在这种方法中，将使用空间换时间来检查融化在100到1000年的时间尺度上的后果。这项研究将为在整个北方气候变暖和动态冻土条件下促进有效的环境监管、土地和水资源管理以及资源开发的科学证据提供信息。

Half of Canadian land sits on permafrost, a layer of frozen soil, water, and rock.  We are a permafrost nation.  Northern Canada is also one of the most rapidly warming regions on Earth, and the stable frozen ground that has fundamentally shaped ecosystems, infrastructure, and resources across the north is thawing at unprecedented rates. Thawing permafrost provides new sources of energy for microbes, which in turn release carbon dioxide and methane to the atmosphere that contribute further to the greenhouse effect.  Known as the "permafrost carbon feedback", this cycle is one of the most likely positive feedbacks from land to the atmosphere with warming. However, the fate of permafrost carbon release as greenhouse gases depends on several key factors, including 1) whether thawing soils become flooded, which could reduce the activity of microbes, 2) whether thawing permafrost creates nutrient-rich conditions, which could stimulate microbial activity, and 3) whether increases in plant growth in response to thaw can help to offset permafrost carbon release. To address these issues, the proposed research will develop a mechanistic understanding of how plants and microbes compete for nutrients under aerobic and anaerobic thaw trajectories in the Northwest Territories and Alaska, two regions where permafrost is experiencing widespread thaw. The research will measure changes in nitrogen and phosphorus availability with permafrost thaw, and the consequences of soil nutrient enrichment on plant and microbial processes. Experimental studies that examine plant and microbial processes in real time will be complemented by a gradient approach, where a space-for-time substitution will be used to examine consequences of thaw on time-scales of 100s to 1000s of years. This research will inform science-based evidence promoting effective environmental regulation, land and water management, and resource development in the face of a warming climate and dynamic permafrost conditions throughout the North.