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The influence of soil processes on carbon isotope distribution and turnover in the British uplands
Author(s) -
Bol R. A.,
Harkness D. D.,
Huang Y.,
Howard D. M.
Publication year - 1999
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1046/j.1365-2389.1999.00222.x
Subject(s) - soil water , podzol , soil carbon , pedogenesis , soil science , total organic carbon , carbon cycle , soil organic matter , carbon fibers , isotopes of carbon , environmental science , soil horizon , environmental chemistry , organic matter , detritus , soil classification , chemistry , ecosystem , geology , ecology , materials science , organic chemistry , biology , composite number , composite material , paleontology
Summary Understanding the natural variation of carbon within the soil, and between soil types, is crucial to improve predictive models of carbon cycling in high and mid‐latitude ecosystems in response to global warming. We measured the carbon isotope distributions ( 12 C, 13 C and 14 C) in soil organic matter (SOM) from Podzols, Brown Podzolic soils and Stagnohumic Gleysols from the British uplands, which were then compared with the total amounts and turnover of carbon in these soils. We did so by sampling at 2‐cm intervals down six profiles of each soil type. The average amount of carbon stored in the top 28 cm of the Stagnohumic Gleysols is twice that of the other two soils. The 13 C content and 14 C age show a general increase with depth in all soils, and there is also a significant correlation between isotopic variation and the main pedogenic features. The latter suggests that soil‐forming processes are significant in determining the carbon isotope signatures retained in SOM. Organic matter formed since 1960 is not found below 5 cm in any of the soils. Evidently organic detritus in the surface layers (LF and Oh) is rapidly mineralized. This accords with our modelled net annual C fluxes which show that more than 80% of the CO 2 emanating from these soils is derived from the top 5 cm of each profile. Although these soils contain much carbon, they do not appear to assimilate and retain SOM rapidly. The mean residence time of most of their carbon is in the 2–50 years range, so the soils are fairly ineffective sinks for excess CO 2 in the atmosphere. Under the predicted future ‘greenhouse’ climate, likely to favour more rapid microbial decomposition of organic materials, these soils are a potential source of CO 2 and are therefore likely to accelerate global warming.