The carbon sinks of North American boreal forests have been threatened by global warming and forest disturbances in recent decades, but knowledge about the carbon balance of these forests in recent years remains unknown. We tracked annual aboveground carbon (AGC) changes from 2016 to 2021 across the forest regions of NASA’s Arctic Boreal Vulnerability Experiment (ABoVE) core study domain, using Vegetation Optical Depth derived from low-frequency passive microwave observations. The results showed that these forests showed a net AGC increase of + 28.49 Tg C/yr during the study period, with total AGC gains of + 219.34 Tg C/yr counteracting total AGC losses of −190.86 Tg C/yr. Forest degradation (-162.21 Tg C/yr), defined as a reduction in the capacity of forest to provide goods and services, contributes 5 times more to the total AGC loss than forest cover loss (-28.65 Tg C/yr), defined as the complete removal of tree cover. This indicates that degradation has dominated AGC loss in the region.

中文翻译：

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在北美北方森林中，森林退化对碳损失的影响大于森林覆盖面积的损失

近几十年来，北美北方森林的碳汇受到全球变暖和森林干扰的威胁，但近年来有关这些森林碳平衡的知识仍然未知。我们使用低频被动微波观测得出的植被光学深度，跟踪了 NASA 北极寒带脆弱性实验 (ABoVE) 核心研究领域森林地区从 2016 年到 2021 年的年度地上碳 (AGC) 变化。结果表明，在研究期间，这些森林的 AGC 净增长为 + 28.49 Tg C/年，AGC 总增益为 + 219.34 Tg C/年，抵消了总 AGC 损失 -190.86 Tg C/年。森林退化（-162.21 Tg C/年）（定义为森林提供商品和服务的能力下降）对 AGC 总损失的影响是森林覆盖损失（-28.65 Tg C/年）的 5 倍，定义为彻底清除树木覆盖物。这表明退化主导了该区域的 AGC 损失。