Thermokarst features are widespread in ice-rich regions of the circumpolar Arctic. The rate of thermokarst lake formation and drainage is anticipated to accelerate as the climate warms. However, it is uncertain how these dynamic features impact the terrestrial Arctic carbon cycle. Methane (CH₄) and carbon dioxide (CO₂) fluxes were measured during peak growing season using eddy covariance and chambers at Illisarvik, a 0.16 km² thermokarst lake basin that was experimentally drained in 1978 on Richards Island, Northwest Territories, Canada. Vegetation in the basin differs markedly from the surrounding dwarf-shrub tundra and included patches of tall shrubs, grasses, and sedges with some bare ground and a small pond in the centre. During the peak growing season, temperature and wind conditions were highly variable, and soil water content decreased steadily. Basin-scaled net ecosystem CO₂ exchange (NEE) measured by eddy covariance was −1.5 [CI_95 %±0.2] g C−CO₂ ${\mathrm{m}}^{-\mathrm{2}}{\mathrm{d}}^{-\mathrm{1}}$; NEE followed a marked diurnal pattern with no day-to-day trend during the study period. Variations in half-hourly NEE were primarily controlled by photosynthetic photon flux density and influenced by vapour pressure deficit, volumetric water content, and the presence of shrubs within the flux tower footprint, which varied with wind direction. Net methane exchange (NME) was low (8.7 [CI_95 %±0.4] $\mathrm{mg}{\mathrm{CH}}_{\mathrm{4}}{\mathrm{m}}^{-\mathrm{2}}{\mathrm{d}}^{-\mathrm{1}}$) and had little impact on the growing season carbon balance of the basin. NME displayed high spatial variability, and sedge areas in the basin were the strongest source of CH₄ while upland areas outside the basin were a net sink. Soil moisture and temperature were the main environmental factors influencing NME. Presently, Illisarvik is a carbon sink during the peak growing season. However, these results suggest that rates of growing season CO₂ and CH₄ exchange rates may change as the basin's vegetation community continues to evolve.

中文翻译：

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植被和环境控制对加拿大西部北极热喀斯特湖排空的温室气体通量的影响

高温岩溶特征广泛分布在北极的冰层丰富地区。随着气候变暖，热喀斯特湖的形成和排水速度有望加快。但是，尚不确定这些动态特征如何影响北极陆地碳循环。在峰值生长季节，使用涡度协方差和伊利萨尔维克（Ellisarvik）0.16 km ^2的气室测量甲烷（CH ₄）和二氧化碳（CO ₂）通量  1978年在加拿大西北地区的理查兹岛（Richards Island）上进行实验性排水的热喀斯特湖盆地。盆地中的植被与周围的矮灌木苔原明显不同，其中包括高矮的灌木，草和莎草，中间有一些裸露的地面和一个小池塘。在高峰生长期，温度和风况变化很大，土壤含水量稳步下降。盆缩放的生态系统净CO ₂ 通过涡协方差测量交换（NEE）为 - 1.5 [CI _95％ ±0.2 ] 克 C-CO ₂ ${\mathrm{米}}^{--\mathrm{2}}{\mathrm{d}}^{--\mathrm{1个}}$; 在研究期间，NEE遵循明显的昼夜模式，没有日常趋势。半小时NEE的变化主要受光合光子通量密度的控制，并受蒸气压不足，体积水含量和通量塔占地面积内灌木的存在的影响，这些随风向而变化。甲烷净交换量（NME）低（8.7 [CI _95％ ±0.4 ] $\mathrm{毫克}{\mathrm{CH}}_{\mathrm{4}}{\mathrm{米}}^{--\mathrm{2}}{\mathrm{d}}^{--\mathrm{1个}}$），对盆地的生长期碳平衡影响不大。NME显示出高度的空间变异性，盆地中的莎草区是CH ₄的最强来源， 而盆地外的高地则是净汇。土壤水分和温度是影响NME的主要环境因素。目前，伊利萨尔维克（Illisarvik）是生长高峰期的碳汇。但是，这些结果表明，随着流域植被群落的不断发展，生长季CO ₂和CH ₄交换率可能会发生变化。