Limited increases in savanna carbon stocks over decades of fire suppression

Savannas cover a fifth of the land surface and contribute a third of terrestrial net primary production, accounting for three quarters of global area burned and over half of global fire-driven carbon emissions. Fire suppression and afforestation have been proposed as tools to increase carbon sequestration in these ecosystems. A robust quantification of whole-ecosystem carbon storage in savannas is lacking, however, especially under altered fire regimes. Here, we provide the first direct estimates of whole-ecosystem carbon response to over 60 years of fire exclusion in a mesic African savanna. We found that fire suppression increased whole-ecosystem carbon storage by only 35.4 ± 12% (mean ± standard error), even though tree cover increased by 78.9 ± 29.3%, corresponding to total gains of 23.0 ± 6.1 Mg C ha-1 at an average ~0.35 ± 0.09 Mg C ha-1 yr-1, more than an order of magnitude lower than previously assumed. Frequently burned savannas had substantial belowground carbon, especially in...热带稀树草原（savanna）覆盖全球五分之一的陆地表面，贡献了陆地净初级生产量的三分之一，同时占据全球过火总面积的四分之三，以及超过一半的全球火灾驱动碳排放。已有研究提出将灭火与造林作为提升此类生态系统碳固存能力的手段。然而，目前学界仍缺乏对热带稀树草原全生态系统碳储量的可靠量化分析，尤其是在火灾格局发生改变的情境下。本研究首次直接估算了湿润型非洲热带稀树草原在超过60年的灭火干预后，全生态系统的碳响应。研究结果显示，尽管树木覆盖率提升了78.9±29.3%，但灭火措施仅使全生态系统碳储量增加了35.4±12%（均值±标准误），对应总碳储量增益为23.0±6.1 Mg C ha⁻¹，年均增益速率约为0.35±0.09 Mg C ha⁻¹ yr⁻¹，该数值较此前学界的假设值低了一个数量级以上。高频火烧的热带稀树草原拥有可观的地下碳储量，尤其是在……