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

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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.