首页|Persistence of old soil carbon under changing climate: The role of mineral-organic matter interactions
Persistence of old soil carbon under changing climate: The role of mineral-organic matter interactions
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NSTL
Elsevier
Globally, soils store between 1500 and 2800 Pg of organic carbon (OC). The physical and chemical stability of these terrestrial soil carbon stores under plausible climate change scenarios is unclear. Soil organic carbon (SOC), especially in volcanic soils, is stabilized through mineral matrix interactions. How susceptible are these mineralorganic matter interactions to environmental change? Here we present a study of SOC age along a climate gradient of andisols from Kohala volcano on the Island of Hawai'i. We measure carbon isotope composition (~(14)C/~(12)C, ~(13)C/~(12)C) in bulk samples and extracted biomarkers for 4-8 horizons of 15 soil profiles to understand variability in SOC age and persistence across incremental differences in mean annual precipitation. Bulk OC in the subsoil has radiocarbon fraction modern (Fm) values as low as 0.28 to 0.16 (~10,160 to ~14,630 conventional radiocarbon years). Coexisting plant-derived long chain fatty acids (LCFAs) are older, over 22,500 yrs. (Fm = 0.060), implying that these are among the most stable compounds in the soil, while corresponding shorterchain (C16) fatty acids are much younger, consistent with an origin from active microbial communities assimilating young OC percolating from surface horizons. There is significant Fe loss at higher mean annual precipitation (MAP) (>2200 mm yr~(-1)) sites associated with episodic soil saturation and microbial Fe reduction. %OC is higher at these sites, consistent with the expectation that saturated conditions promote SOC storage. However, in these higher MAP sites iron depletion is associated with much younger bulk SOC and LCFAs ~(14)C ages (~2900 ~(14)C years) than at equivalent sample depths in sites that retain most Fe (~14,200 ~(14)C years). The remaining mineral matrix consists primarily of Si, Al, and Ti as SRO minerals. The data imply that modest increases in precipitation resulting from environmental change at locations near a potential saturation or redox threshold coul
Persistenceclimatemineral-organic
Katherine E. Grant、Valier V. Galy、Negar Haghipour、Timothy I. Eglinton、Louis A. Derry
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Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA
Geological Institute, ETH-Zurich, Zurich, Switzerland
NSTL
Elsevier
