Warming conditions across Canada's subarctic and arctic regions are causing permafrost landforms to thaw, resulting in rapid land cover change, including conversion of peat plateaus to wetland and thermokarst. These changes have important implications for northern ecosystems, including shifting controls on carbon uptake and release functions, as well as altering evapotranspiration (ET) rates, which form feedbacks with climatic change. Four landforms (peat plateau, sedge lawn, channel fen, and a thermokarst shoreline collapse scar) in the Hudson Bay Lowlands, northern Manitoba, were instrumented for weekly chamber measurements of carbon dioxide (CO₂) and water vapor flux over a summer season (May to September 2014). Relative to other landforms, thermokarst CO₂ exchange was characterized by high respiration rates early in the season, which decreased and were offset later in the season by CO₂ uptake driven by sedge productivity. For all landforms, ET peaked post‐snowmelt during rapid active layer thaw, and decreased throughout the growing season, controlled primarily by atmospheric vapor deficits. This work shows distinct differences in CO₂ exchange and ET between intact and thawing permafrost features. While representative of small‐scale processes in a single study region over one growing season, the results presented in this study have important implications for our understanding of ecohydrological and biogeochemical functioning of subarctic landscapes under future climates.

中文翻译：

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西哈德逊湾低地融化和完整的多年冻土地貌之间生长季节的二氧化碳交换和蒸散动态

加拿大南极和北极地区的变暖条件导致多年冻土地貌融化，导致土地覆被迅速变化，包括将泥炭高原转化为湿地和喀斯特地貌。这些变化对北方生态系统具有重要意义，包括改变对碳吸收和释放功能的控制，以及改变蒸散量（ET），从而形成与气候变化有关的反馈。在曼尼托巴省北部哈德逊湾低地，对四个地形（豌豆高原，莎草草坪，芬河通道和热喀斯特海岸线塌陷疤痕）进行了仪器测量，以测量夏季每个星期的二氧化碳（CO ₂）和水蒸气通量（ 2014年5月至2014年9月）。相对于其他地形，热喀斯特CO ₂交换的特点是在季节初期呼吸频率高，而在莎草生产力的驱动下，这种呼吸频率下降并在本季节后期被CO ₂吸收所抵消。对于所有地貌，ET在快速活动层融化期间在融雪后达到顶峰，并在整个生长季节下降，这主要受大气蒸汽亏缺的控制。这项工作显示了完整和解冻的永久冻土特征之间的CO ₂交换和ET的明显差异。尽管代表了一个研究区域在一个生长季节内的小规模过程，但这项研究中提出的结果对于我们对未来气候下亚北极景观的生态水文和生物地球化学功能的理解具有重要意义。