Stabilization Mechanisms and Decomposition Potential of Eroded Soil Organic Matter Pools in Temperate Forests of the Sierra Nevada, California. Issue 1 (3rd January 2019)

• Record Type: Journal Article
• Authors: Stacy, Erin M.; Berhe, Asmeret Asefaw; Hunsaker, Carolyn T.; Johnson, Dale W.; Meding, S. Mercer; Hart, Stephen C.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 1(2019)
• Page Start: 2
• Page End: 17
• Publication Date: 2019-01-03
• Subjects: erosion -- stabilization -- soil organic matter -- montane -- temperate coniferous forests; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2018JG004566
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: The lateral destination and potential decomposition of soil organic matter mobilized by soil erosion depends on factors such as the amount and type of precipitation, topography, the nature of mobilized organic matter (OM), potential mixing with mineral particles, and the stabilization mechanisms of the soil OM. This study examined how the relative distribution of carbon (C) and nitrogen (N) in different OM fractions varied in soils from eroding slopes and in eroded sediments in a series of low‐order forested catchments in the western Sierra Nevada, California. We found that precipitation amount played a major role in mobilizing OM. More than 40% of the OM exported from these forested catchments was free particulate OM, or OM physically protected inside relatively less stable macroaggregates, compared to OM inside microaggregates or chemically associated with soil minerals. Years with high amounts of precipitation generally transported more mineral‐associated OM, with lower C and N concentrations, while sediment transported in drier years was more enriched in unprotected, coarse particulate OM derived from surficial soils. When incubated under the same conditions, sediment C (from material captured in settling basins) produced 72–97% more CO2 during decomposition than soil C did. Our results suggest that without stabilization through burial or reconfigured organomineral associations, this sediment OM is prone to decomposition, which may contribute to little to no terrestrial CO2 sink induced from erosion in these Mediterranean montane forest ecosystems. Key Points: Most carbon and nitrogen eroded from the upland catchments was either unprotected or physically protected inside weak macroaggregates Amount of eroded organic matter varied by year, but stabilization mechanisms did not vary consistently with type or amount of precipitation Organic matter in sediment was more readily decomposable than soil organic matter under similar environmental conditions