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The relationship between soil heterotrophic activity, soil dissolved organic carbon (DOC) leachate, and catchment‐scale DOC export in headwater catchments
Author(s) -
Brooks P. D.,
McKnight D. M.,
Bencala K. E.
Publication year - 1999
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/1998wr900125
Subject(s) - dissolved organic carbon , snowmelt , environmental science , hydrology (agriculture) , soil water , leaching (pedology) , soil carbon , weathering , geology , soil science , snow , geomorphology , oceanography , geotechnical engineering
Dissolved organic carbon (DOC) from terrestrial sources forms the major component of the annual carbon budget in many headwater streams. In high‐elevation catchments in the Rocky Mountains, DOC originates in the upper soil horizons and is flushed to the stream primarily during spring snowmelt. To identify controls on the size of the mobile soil DOC pool available to be transported during the annual melt event, we measured soil DOC production across a range of vegetation communities and soil types together with catchment DOC export in paired watersheds in Summit County, Colorado. Both surface water DOC concentrations and watershed DOC export were lower in areas where pyrite weathering resulted in lower soil p H. Similarly, the amount of DOC leached from organic soils was significantly smaller ( p < 0.01) at sites having low soil p H. Scaling point source measurements of DOC production and leaching to the two basins and assuming only vegetated areas contribute to DOC production, we calculated that the amount of mobile DOC available to be leached to surface water during melt was 20.3 g C m −2 in the circumneutral basin and 17.8 g C m −2 in the catchment characterized by pyrite weathering. The significant ( r 2 =0.91 and p < 0.05), linear relationship between over‐winter CO 2 flux and the amount of DOC leached from upper soil horizons during snowmelt suggests that the mechanism for the difference in production of mobile DOC was heterotrophic processing of soil carbon in snow‐covered soil. Furthermore, this strong relationship between over‐winter heterotrophic activity and the size of the mobile DOC pool present in a range of soil and vegetation types provides a likely mechanism for explaining the interannual variability of DOC export observed in high‐elevation catchments.