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

加拿大一半的土地坐落在永久冻土上，这是一层冻结的土壤、水和岩石。我们是一个永久冻土的国家。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的生态系统、基础设施和资源的稳定冻土正在以前所未有的速度融化。永久冻土的融化为微生物提供了新的能量来源，而微生物又向大气中释放二氧化碳和甲烷，进一步加剧了温室效应。这个循环被称为“永久冻土碳反馈”，它是随着气候变暖从陆地到大气的最可能的正反馈之一。然而，作为温室气体的永久冻土碳释放的命运取决于几个关键因素，包括1)融化的土壤是否会被淹没，这可能会减少微生物的活动；2)融化的永久冻土是否会创造富含营养的条件，这可能会刺激微生物的活动；3)响应融化的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，拟议的研究将对西北地区和阿拉斯加的植物和微生物如何在好氧和厌氧融化轨迹下争夺营养物质进行机制理解，这两个地区的永久冻土正在经历广泛的融化。该研究将测量随着永久冻土融化氮和磷有效性的变化，以及土壤养分富集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，其中将使用空间代替时间的方法在100年至1000年的时间尺度上检查解冻的后果。这项研究将为基于科学的证据提供信息，在整个北方气候变暖和永冻土不断变化的情况下，促进有效的环境监管、土地和水管理以及资源开发。

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.