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Koarashi, Jun; Hockaday, W.*; Masiello, C.*; Trumbore, S.*
Journal of Geophysical Research; Biogeosciences, 117, p.G03033_1 - G03033_13, 2012/09
Times Cited Count：47 Percentile：78.15(Environmental Sciences)Subsurface horizons contain more than half of the global soil carbon (C), yet the dynamics of this C remains poorly understood. We estimated the amount of decadally-cycling subsurface C from the incorporation of "bomb' radiocarbon (
C) using samples taken over 50 years from grassland and forest soils in the Sierra Nevada Mountains, California. The C content of all organic matter fractions increased from the pre- to post-bomb samples, indicating about half of the subsoil C consists of C fixed since 1963. The C content of mineral-associated C increased rapidly from 1992-2009, indicating a significant time lag (
20 years) for the arrival of "bomb" C to this fraction. Our results demonstrate that a lagged response of the large subsurface C stores to changes in environmental conditions is possible.
Koarashi, Jun; Trumbore, S. E.*
no journal, ,
no abstracts in English
Trumbore, S.*; Schrumpf, M.*; Khomo, L.*; Koarashi, Jun
no journal, ,
Carbon content usually declines, and its age increases, with depth in soil profiles. These patterns reflect the operation of several different depth-dependent processes. We compare the depth trends of carbon and C-14 in density-fractionated soils sampled from locations that vary in parent material/mineralogy and vegetation/climate and use whole-profile averages to identify patterns across a range of edaphic factors. The depth-profile of the free light fraction is similar to that of roots, and its age remains modern regardless of soil depth. In contrast, the radiocarbon age of C associated with minerals, or occluded within aggregates, increases in most soils almost linearly with depth. The slope of C-14 in the mineral fraction versus depth is potentially a metric useful for distinguishing among mechanisms responsible for C stabilization.
