Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA.
Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, USA.
Nat Commun. 2024 Aug 17;15(1):7084. doi: 10.1038/s41467-024-51422-6.
Tropical forests account for over 50% of the global terrestrial carbon sink, but climate change threatens to alter the carbon balance of these ecosystems. We show that warming and drying of tropical forest soils may increase soil carbon vulnerability, by increasing degradation of older carbon. In situ whole-profile heating by 4 °C and 50% throughfall exclusion each increased the average radiocarbon age of soil CO efflux by ~2-3 years, but the mechanisms underlying this shift differed. Warming accelerated decomposition of older carbon as increased CO emissions depleted newer carbon. Drying suppressed decomposition of newer carbon inputs and decreased soil CO emissions, thereby increasing contributions of older carbon to CO efflux. These findings imply that both warming and drying, by accelerating the loss of older soil carbon or reducing the incorporation of fresh carbon inputs, will exacerbate soil carbon losses and negatively impact carbon storage in tropical forests under climate change.
热带雨林占全球陆地碳汇的 50%以上，但气候变化可能会改变这些生态系统的碳平衡。我们表明，通过增加对旧碳的降解，热带森林土壤的变暖变干可能会增加土壤碳的脆弱性。通过原位全剖面加热 4°C 和减少 50%的穿透降水，土壤 CO 排放的平均放射性碳年龄分别增加了约 2-3 年，但这种转变的机制不同。变暖加速了旧碳的分解，因为 CO 排放的增加耗尽了新碳。干燥抑制了新碳输入的分解，减少了土壤 CO 的排放，从而增加了旧碳对 CO 排放的贡献。这些发现表明，变暖变干都会加速旧土壤碳的损失或减少新碳输入的结合，从而加剧土壤碳的损失，并对气候变化下的热带森林的碳储存产生负面影响。
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