Realistic representation of land carbon sink in climate models is vital for predicting carbon climate feedbacks in a changing world. Although soil erosion that removes land organic carbon has increased substantially since the onset of agriculture, it is rarely included in the current generation of climate models. Using an Earth system model (ESM) with soil erosion represented, we estimated that on average soil erosion displaces 5% of newly fixed land organic carbon downslope annually in the continental United States. In the lower Mississippi river basin and the Cascades, the fraction can be as large as 40%. About 12% of the eroded organic carbon is eventually exported to inland waters, which is equal to 14% of the simulated net carbon gain by terrestrial ecosystems. By comparing the eroded organic carbon export to rivers with the particulate organic carbon export to oceans, we demonstrated that a large fraction of the carbon export to rivers could have been mineralized in inland waters. Importantly, with a direct comparison of eroded and exported soil organic carbon and land net carbon uptake, we found that ESMs that ignore soil erosion likely offset the erosional carbon loss by increasing heterotrophic respiration implicitly. But as soil erosion and heterotrophic respiration respond differently to a warming climate, this unrealistic compensation would lead to biased predictions of future land carbon sink.

中文翻译：

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土壤侵蚀对土地碳汇的实质性作用及其未来变化.

气候模型中陆地碳汇的真实表示对于预测不断变化的世界中的碳气候反馈至关重要。尽管自农业出现以来，导致土地有机碳流失的土壤侵蚀大幅增加，但它很少被纳入当前一代的气候模型中。使用以土壤侵蚀为代表的地球系统模型 (ESM)，我们估计美国大陆每年平均土壤侵蚀会取代新固定土地有机碳的 5%。在密西西比河下游流域和喀斯喀特地区，这一比例可能高达 40%。大约12%的被侵蚀的有机碳最终被输出到内陆水域，相当于陆地生态系统模拟净碳增益的14%。通过比较向河流输出的侵蚀有机碳与向海洋输出的颗粒有机碳，我们证明向河流输出的碳的很大一部分可能在内陆水域矿化。重要的是，通过直接比较侵蚀和输出的土壤有机碳和土地净碳吸收，我们发现忽略土壤侵蚀的ESM可能通过隐含地增加异养呼吸来抵消侵蚀性碳损失。但由于土壤侵蚀和异养呼吸对气候变暖的反应不同，这种不切实际的补偿将导致对未来土地碳汇的预测出现偏差。