Influence of changing active-layer thickness on PERmafrost PeatLand trace gas EXchanges and carbonbalance (PERPLEX)

几千年来，北方和亚北极泥炭地一直扮演着长期碳(C)汇的角色，因为每年的净初级生产量已经超过了二氧化碳（CO2）和甲烷（CH4）的呼吸损失以及侧向碳损失。加拿大北部泥炭地的很大一部分是永久冻土（永久冻土），在短暂的生长季节里，顶部会季节性地融化。由于持续的气候变化，这一具有渗透性和生物地球化学活性的顶层厚度增加，将使额外的有机碳暴露于微生物分解和泥炭地水文变化中，从而对泥炭地生态生理和生物地球化学过程产生严重后果。活土层加深对永久冻土泥炭地CO2和CH4汇源强度命运的影响在很大程度上是未知的。拟议的研究项目将阐明泥炭地-大气相互作用如何受到活动层厚度增加的影响（随着泥炭剖面下降到霜表的最大深度）。使用安装在加拿大西部不连续永久冻土带两个地点的两套相同的仪器，将使用涡动相关方差技术在永久冻土带高原和附近的无永久冻土带测量CO2、CH4、水和能量的净交换。测量技术的最新前沿发展产生了新的坚固的传感器和分析仪，专为在偏远地区恶劣条件下使用该技术而设计。辅助水文和光谱测量结合对植被组成和结构、积雪、地表和霜面地形的定期调查，将有助于建立持续的永久冻土退化与泥炭地CO2和CH4汇源强度和碳平衡之间的联系。这一知识对于将加拿大巨大的泥炭地C储存在该国的温室气体清单中是迫切需要的。

For millennia, boreal and subarctic peatlands have been acting as long-term carbon (C) sink because annually net primary production has been exceeding respiratory losses of carbon dioxide (CO2) and methane (CH4) and lateral C losses. A large portion of Canada's northern peatlands is underlain by permanently frozen ground (permafrost) that thaws seasonally at the top over a short growing season. Increases in the thickness of this permeable and biogeochemically active top layer due to ongoing climate change will have severe consequences for peatland ecophysiological and biogeochemical processes by exposing additional organic C to microbial decomposition and by altered peatland hydrology. The impact of a deepening active layer on the fate of permafrost peatlands' CO2 and CH4 sink-source strengths is largely unknown. The proposed research project will shed light on how peatland-atmosphere interactions are affected by increasing active-layer thickness (maximum depth to frost table as it descends through the peat profile). Using two identical sets of instrumentation installed at two sites in the discontinuous permafrost zone of western Canada, the net exchanges of CO2, CH4, water and energy will be measured over a permafrost peat plateau and a nearby permafrost-free peatland with the eddy covariance technique. Recent cutting-edge developments in measurement technology resulted in new robust sensors and analyzers designed for use of this technique under harsh conditions in remote locations. Ancillary hydrological and spectral measurements in combination with regular surveys of vegetation composition and structure, snow pack, and surface and frost table topography will aid in establishing the link between continued permafrost degradation and peatlands' CO2 and CH4 sink-source strengths and C balance. This knowledge is urgently needed for including Canada's vast peatland C store in the country's greenhouse gas inventory.