The boreal biome exchanges large amounts of carbon (C) and greenhouse gases (GHGs) with the atmosphere and thus significantly affects the global climate. A managed boreal landscape consists of various sinks and sources of carbon dioxide (CO2 ), methane (CH4 ), and dissolved organic and inorganic carbon (DOC and DIC) across forests, mires, lakes, and streams. Due to the spatial heterogeneity, large uncertainties exist regarding the net landscape carbon balance (NLCB). In this study, we compiled terrestrial and aquatic fluxes of CO2 , CH4 , DOC, DIC, and harvested C obtained from tall-tower eddy covariance measurements, stream monitoring, and remote sensing of biomass stocks for an entire boreal catchment (~68 km2 ) in Sweden to estimate the NLCB across the land-water-atmosphere continuum. Our results showed that this managed boreal forest landscape was a net C sink (NLCB = 39 g C m-2 year-1 ) with the landscape-atmosphere CO2 exchange being the dominant component, followed by the C export via harvest and streams. Accounting for the global warming potential of CH4 , the landscape was a GHG sink of 237 g CO2 -eq m-2 year-1 , thus providing a climate-cooling effect. The CH4 flux contribution to the annual GHG budget increased from 0.6% during spring to 3.2% during winter. The aquatic C loss was most significant during spring contributing 8% to the annual NLCB. We further found that abiotic controls (e.g., air temperature and incoming radiation) regulated the temporal variability of the NLCB whereas land cover types (e.g., mire vs. forest) and management practices (e.g., clear-cutting) determined their spatial variability. Our study advocates the need for integrating terrestrial and aquatic fluxes at the landscape scale based on tall-tower eddy covariance measurements combined with biomass stock and stream monitoring to develop a holistic understanding of the NLCB of managed boreal forest landscapes and to better evaluate their potential for mitigating climate change.

中文翻译：

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净景观碳平衡——整合瑞典管理的北方森林景观中的陆地和水生碳通量。

北方生物群落与大气交换大量碳（C）和温室气体（GHG），从而显着影响全球气候。受管理的北方景观由森林、沼泽、湖泊和溪流中二氧化碳 (CO2 )、甲烷 (CH4 ) 以及溶解的有机和无机碳 (DOC 和 DIC) 的各种汇和源组成。由于空间异质性，净景观碳平衡（NLCB）存在很大的不确定性。在本研究中，我们通过高塔涡流协方差测量、河流监测和整个北方流域（约 68 平方公里）生物量储量的遥感获得了 CO2、CH4、DOC、DIC 和收获的 C 的陆地和水生通量。在瑞典估计了整个陆地-水-大气连续体的 NLCB。我们的结果表明，这种管理的北方森林景观是一个净碳汇（NLCB = 39 g C m-2year-1），景观-大气二氧化碳交换是主要组成部分，其次是通过收获和溪流的碳输出。考虑到 CH4 的全球变暖潜力，该景观是 237 g CO2 -eq m-2year-1 的温室气体汇，从而提供了气候冷却效应。CH4 通量对年度温室气体预算的贡献从春季的 0.6% 增加到冬季的 3.2%。春季水生碳损失最为显着，占年度 NLCB 的 8%。我们进一步发现，非生物控制（例如，气温和传入辐射）调节了NLCB的时间变异性，而土地覆盖类型（例如，泥沼与森林）和管理实践（例如，皆伐）决定了它们的空间变异性。我们的研究主张需要根据高塔涡流协方差测量结合生物量库和溪流监测，在景观尺度上整合陆地和水生通量，以全面了解管理的北方森林景观的 NLCB，并更好地评估其潜力减缓气候变化。