Siberian forests are generally thought to have acted as an important carbon sink over recent decades, but exposure to severe droughts and fire disturbances may have impacted their carbon dynamics. Limited available forest inventories mean the carbon balance remains uncertain. Here we analyse annual live and dead above-ground carbon changes derived from low-frequency passive microwave observations from 2010 to 2019. We find that during this period, the carbon balance of Siberian forests was close to neutral, with the forests acting as a small carbon sink of \(+ 0.02_{ + 0.01}^{ + 0.03}\) PgC yr⁻¹. Carbon storage in dead wood increased, but this was largely offset by a decrease in live biomass. Substantial losses of live above-ground carbon are attributed to fire and drought, such as the widespread fires in northern Siberia in 2012 and extreme drought in eastern Siberia in 2015. These live above-ground carbon losses contrast with ‘greening’ trends seen in leaf area index over the same period, a decoupling explained by faster post-disturbance recovery of leaf area than live above-ground carbon. Our study highlights the vulnerability of large forest carbon stores in Siberia to climate-induced disturbances, challenging the persistence of the carbon sink in this region of the globe.

近几十年来，西伯利亚森林通常被认为是重要的碳汇，但遭受严重干旱和火灾干扰可能会影响其碳动态。有限的可用森林存量意味着碳平衡仍然不确定。在这里，我们分析了 2010 年至 2019 年低频被动微波观测得出的年度地上活碳和死碳变化。我们发现，在此期间，西伯利亚森林的碳平衡接近中性，森林作为一个小的\(+ 0.02_{ + 0.01}^{ + 0.03}\) PgC yr ⁻¹的碳汇. 死木中的碳储量增加，但这在很大程度上被活生物量的减少所抵消。地上活碳的大量损失归因于火灾和干旱，例如 2012 年西伯利亚北部的大范围火灾和 2015 年西伯利亚东部的极端干旱。这些地上活碳损失与叶子中看到的“绿化”趋势形成对比同一时期的面积指数，这是一种解耦，其原因是叶面积的干扰后恢复速度比活的地上碳更快。我们的研究强调了西伯利亚大型森林碳储存对气候引起的干扰的脆弱性，挑战了全球这一地区碳汇的持久性。