发现热带和寒带森林自2000年起转为碳源，威胁全球碳平衡。
Decadal sink-source shifts of forest aboveground carbon since 1988
- 融合多源卫星与深度学习，重建1988-2021年全球森林碳储量
- 全球森林累计吸收6.2亿吨碳，但热带与寒带森林已转为碳源
- 亚马逊原始林贡献碳损失波动超七成，远超砍伐区
森林生态系统对全球碳循环至关重要，但其长期地上碳（AGC）动态仍不明确。本文整合多源卫星观测与概率性深度学习模型，重建了1988至2021年全球森林AGC记录，空间分辨率为0.25度。结果显示，尽管全球森林累计吸收6.2 PgC，湿润热带与寒带森林自21世纪初起逐渐转变为碳源。这一转变与热带地区AGC变化与大气CO2增长速率的负相关性增强相吻合（2011–2021年r = -0.63），表明热带森林正日益影响全球碳循环。特别地，在巴西亚马逊地区，原始林对年际碳损失波动的贡献从1990年代的33%上升至2010年代的76%，超过砍伐区域（从60%降至13%）。研究揭示关键生物群落碳储量的脆弱性，并为监测人类气候背景下碳汇/源转变提供了基准。
原文摘要 · Abstract (English)
Forest ecosystems are vital to the global carbon cycle, yet their long-term aboveground carbon (AGC) dynamics remain uncertain. Here, we integrate multi-source satellite observations with probabilistic deep learning models to reconstruct a harmonized, uncertainty-aware global forest AGC record from 1988 to 2021 at 0.25-deg. We find that, although global forests sequestered 6.2 PgC, moist tropical and boreal forests have progressively transitioned toward carbon sources since the early 2000s. This shift coincides with a strengthening negative correlation between tropical AGC variability and atmospheric CO2 growth rates (r = -0.63 in 2011-2021), suggesting tropical forests increasingly modulate the global carbon cycle. Notably, in the Brazilian Amazon, the contribution of intact forests to the year-to-year variations in AGC losses increased from 33% in the 1990s to 76% in the 2010s, surpassing that of deforested areas (from 60% to 13%). Our findings highlight the vulnerability of carbon stocks in key biomes and provide a benchmark to track emerging sink-source shifts under anthropogenic climate change.
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