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层上，这是一层冻结的土壤，水和岩石。 我们是一个永冻的国家。 加拿大北方也是地球上变暖最快的地区之一，从根本上塑造了整个北方的生态系统、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。 这种循环被称为“永久冻土碳反馈”，是随着变暖从陆地到大气的最有可能的正反馈之一。 然而，永久冻土碳释放作为温室气体的命运取决于几个关键因素，包括1）融化的土壤是否被淹没，这可能会减少微生物的活动，2）融化的永久冻土是否创造了营养丰富的条件，这可能会刺激微生物的活动，以及3）植物生长的增加是否有助于抵消永久冻土碳释放。为了解决这些问题，拟议的研究将开发一个机械理解植物和微生物如何在西北地区和阿拉斯加的有氧和厌氧解冻轨迹下竞争营养物质，这两个地区的永久冻土正在经历广泛的解冻。 这项研究将测量氮和磷的可用性与永冻层融化的变化，以及土壤养分富集对植物和微生物过程的影响。在真实的时间内检查植物和微生物过程的实验研究将通过梯度方法进行补充，其中空间换时间替代将用于检查100到1000年时间尺度上解冻的后果。这项研究将为促进有效的环境监管，土地和水管理以及资源开发提供科学依据，以应对整个北方的气候变暖和动态永久冻土条件。

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.**