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一直超过二氧化碳(CO2)和甲烷(CH4)的呼吸损失以及横向的C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)的覆盖，在很短的生长季节里，这些冻土在顶部季节性融化。由于持续的气候变化，这种具有渗透性和生物地球化学活性的表层厚度增加，将使更多的有机碳暴露于微生物分解和泥炭地水文变化，从而对泥炭地的生态生理和生物地球化学过程产生严重后果。不断加深的活动层对永久冻土泥炭地二氧化碳和甲烷汇-源强度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跃层厚度(泥炭剖面下降时到霜表的最大深度)的影响。利用安装在加拿大西部不连续多年冻土地带两个地点的两套相同的仪器，将利用涡旋协方差技术测量永久冻土泥炭高原和附近无永久冻土泥炭地的二氧化碳、甲烷、水和能量的净交换。最近测量技术的前沿发展导致了新的坚固耐用的传感器和分析仪，这些传感器和分析仪设计用于在偏远地区的恶劣条件下使用这项技术。辅助的水文和光谱测量，结合对植被组成和结构、积雪、地表和霜表地形的定期调查，将有助于建立持续的冻土退化与泥炭地二氧化碳和甲烷汇-源强度和碳平衡之间的联系。要将加拿大巨大的泥炭地C储存纳入该国的温室气体清单，迫切需要这种知识。

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.