Mineral-organic matter associations in eroding hillslopes: findings from headwater catchments in the Southern Sierra Nevada (Invited)
Abstract
Mineral-organic matter (OM) associations--physical encapsulation of OM inside soil aggregates and chemical bonding and complexation of organic functional groups with soil minerals--determine the proportion of soil organic matter (SOM) that is redistributed and mineralized during and after erosional transport of sediments downhill, as well as the stability of the eroded SOM post-deposition. The susceptibility of SOM to decomposition and its stabilization mechanisms can change during and after erosion as a result of: aggregate breakdown or detachment due to kinetic energy of raindrops and/or shearing during lateral transport, and reconfiguration of mineral-OM associations through formation of new and strengthening of existing mineral-OM associations in depositional environments that are enriched in carbon (C) and reactive soil minerals. The goal of this study was to determine how concentration, nature and distribution of SOM in soil fractions vary between eroding slopes and sediments exported from eroding catchments. Free organic particles exported from eroding watersheds typically represent <30% of total carbon mobilized by erosion, compared to <20% mobilized as aggregate protected C and <30% as C complexed with Fe and Al oxides. Our results show that there is large variability in nature of exported material across eight headwater catchments that is not directly related to watershed size or climatic variability. In addition, we quantified the rate at which different OM fractions are preferentially transported and can be potentially lost through decomposition during lateral transport.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B21H..02B
- Keywords:
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- 0428 BIOGEOSCIENCES Carbon cycling;
- 0486 BIOGEOSCIENCES Soils/pedology;
- 1815 HYDROLOGY Erosion