Permafrost carbon-climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics
Permafrost carbon-climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics
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DOI：
10.1073/pnas.1415123112
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发表时间：
2015-03-24
影响因子：
11.1
通讯作者：
Riley, William J.
中科院分区：
文献类型：
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作者：
Koven, Charles D.;Lawrence, David M.;Riley, William J.
永久冻土含有大量的有机碳，其稳定性取决于保持冻结状态。随着未来的变暖，这些土壤可能会向大气中释放碳，并对气候变化起到积极的反馈作用。显著的不确定性仍然对解冻后的碳动态的永冻影响的生态系统，特别是因为大多数的碳驻留在深度分解动力学可能不同于表层土壤，因为氮矿化分解可能会提高植物生长。在这里，我们表明，使用碳-氮模型，包括永久冻土过程中被迫在一个未缓解的变暖的情况下，永久冻土地区的未来碳平衡是高度敏感的深层碳的分解，净平衡范围从21 Pg C到164 Pg C的损失，到2300年。土壤氮矿化的增加减少了养分的限制，但深层氮对碳收支的影响很小，这是由于表层土壤变暖和深层氮供应与植物氮需求之间的季节性差异增强了氮的可用性。虽然氮动态是高度不确定的，该地区未来的碳平衡预计将更多地取决于冻土融化和土壤分解的速度和程度，而不是增强氮的供应，为植被生长所造成的冻土融化。
Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon-nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw.