Mineralization of ancient carbon in the subsurface of riparian forests
Figure S1: Correlation between 13C-DIC, and 14C-DIC in ambient groundwater in 2002 and 2003 at Glaciofluvial (plus signs, GF-1) and alluvial (diamonds, AL-1) sites. (542.2Kb)
Table S1: Cation concentrations (mg L−1), temperature (deg C), and specific conductance (uS) in ambient groundwater in August–Sept 2003 at Glaciofluvial (GF) and Alluvial (AL) riparian zones. (1.345Kb)
Gurwick, Noel P.
McCorkle, Daniel C.
Groffman, Peter M.
Gold, Arthur J.
Kellogg, D. Q.
MetadataShow full item record
Microbial activity in saturated, subsurface sediments in riparian forests may be supported by recent photosynthate or ancient (>500 ybp) soil organic carbon (SOC) in buried horizons. Metabolism of ancient SOC may be particularly important in riparian zones, considered denitrification hot spots, because denitrification in the riparian subsurface is often C-limited, because buried horizons intersect deep flow paths, and because low C mineralization rates can support ecosystem-relevant rates of denitrification. Buried horizons are common where alluvial processes (stream migration, overbank flow) have dominated riparian evolution. Our objectives were to determine: (1) the extent to which ancient SOC directly supports subsurface microbial activity; (2) whether different C sources support microbial activity in alluvial versus glaciofluvial riparian zones; and (3) how microbial use of ancient SOC varies with depth. In situ groundwater incubations and 14C dating of dissolved inorganic carbon revealed that ancient SOC mineralization was common, and that it constituted 31–100% of C mineralization 2.6 m deep at one site, at rates sufficient to influence landscape N budgets. Our data failed to reveal consistent spatial patterns of microbially available ancient C. Although mineralized C age increased with depth at one alluvial site, we observed ancient C metabolism 150 cm deep at a glaciofluvial site, suggesting that subsurface microbial activity in riparian zones does not vary systematically between alluvial and glaciofluvial hydrogeologic settings. These findings underscore the relevance of ancient C to contemporary ecosystem processes and the challenge of using mappable surface features to identify subsurface ecosystem characteristics or riparian zone N-sink strength.
Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): G02021, doi:10.1029/2007JG000482.
Suggested CitationJournal of Geophysical Research 113 (2008): G02021
Showing items related by title, author, creator and subject.
Nagy, R. Chelsea; Porder, Stephen; Neill, Christopher; Brando, Paulo; Quintino, Raimundo Mota; do Nascimento, Sebastiao Aviz (Ecological Society of America, 2015-09)Deforestation and fragmentation influence the microclimate, vegetation structure, and composition of remaining patches of tropical forest. In the southern Amazon, at the frontier of cropland expansion, forests are converted ...
Fate of nitrogen in riparian forest soils and trees : an N-15 tracer study simulating salmon decay Drake, Deanne C.; Naiman, Robert J.; Bechtold, J. Scott (2005-05-23)We introduced a 15N-NH4+ tracer to the riparian forest of a salmon-bearing stream (Kennedy Creek, Washington, USA) to quantify the cycling and fate of a late-season pulse of salmon-N, and, ultimately, mechanisms regulating ...
Isotopic signals in an agricultural watershed suggest denitrification is locally intensive in riparian areas but extensive in upland soils Sigler, W. Adam; Ewing, Stephanie A.; Wankel, Scott D.; Jones, Clain A.; Leuthold, Sam J.; Brookshire, E. N. Jack; Payn, Robert A. (Springer, 2022-02-11)Nitrogen loss from cultivated soils threatens the economic and environmental sustainability of agriculture. Nitrate (NO3−) derived from nitrification of nitrogen fertilizer and ammonified soil organic nitrogen may be lost ...