Sources of soil organic matter transported by soil erosion in fire-prone upland ecosystems of the Sierra Nevada

侵蚀导致的土壤有机质横向再分配控制着自然和人为干扰生态系统中土壤碳储量、稳定性和稳定机制。对侵蚀和火灾对土壤有机质动力学的交互作用知之甚少。然而，了解火灾和侵蚀耦合过程如何影响火灾易发生态系统中土壤有机质的稳定性和稳定机制是至关重要的，因为土壤有机质的稳定性和稳定机制（包括有机质与土壤矿物质通过聚集的物理关系和通过有机官能团与金属氧化物的化学络合作用）决定了1)在火灾中燃烧的土壤有机质的数量；2)沉积物下坡侵蚀输运过程中再分配和矿化的土壤有机质比例；3)侵蚀和沉积土壤有机质的稳定性。在这个项目中，我们的目标是确定流域大小和侵蚀的OM来源对土壤OM动力学的影响，主要是在加利福尼亚州的国王河实验流域。了解控制侵蚀有机质来源变化的土壤学、水文、气候和地貌因素是至关重要的，因为这些因素可以影响土壤侵蚀动员的有机质的浓度和组成，以及其在侵蚀沉积物中的富集。这反过来又对确定侵蚀是使受火灾影响的生态系统成为大气二氧化碳的来源还是汇具有重要意义。除了解决这些问题外，作为本研究的一部分收集的数据将作为研究规定的森林火灾对土壤有机质动态在短期和长期时间尺度上的影响的基准。

Lateral redistribution of soil organic matter (OM) by erosion controls soil carbon stocks, stability, and mechanisms of stabilization in both natural and anthropogenically disturbed ecosystems. Little is known about the interactive effects of erosion and fire on dynamics of soil OM. Yet it is critical to understand how the coupled processes of fire and erosion affect stability and stabilization mechanisms of soil OM in fire-prone ecosystems because stability and stabilization mechanisms of soil OM (including the association of OM with soil minerals physically through aggregation and chemically through complexation of organic functional groups with metal oxides) determine 1) amount of soil OM that is combusted during fires, 2) proportion of soil OM that is redistributed and mineralized during erosional transport of sediments downhill, and 3) stability of eroded and deposited soil OM. In this project, we aim to determine the effect of watershed size and source of eroded OM on soil OM dynamics primarily in the Kings River Experimental Watershed in California. It is critical to develop an understanding of the pedologic, hydrologic, climatic, and geomorphic factors that control variability in source of eroded organic matter (OM), as these factors can influence concentration and composition of OM mobilized by soil erosion, and its enrichment in eroded sediments. This, in turn, has significant implications for determining whether erosion renders fire-affected ecosystems sources or sinks for atmospheric carbon dioxide. In addition to tackling these questions, data collected as part of this study will serve as benchmark for studying the effect of prescribed forest fires on soil OM dynamics over short and long timescales.