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Soil organic carbon decomposition from recently added and older sources estimated by Î´Â¹Â³C values of COâ and organic matter
- Pausch, Johanna, Kuzyakov, Yakov
- Soil biology & biochemistry 2012 v.55 pp. 40-47
- carbon dioxide, soil organic carbon, models, fallow, corn, microorganisms, soil depth, wheat, soil sampling, roots, vegetation, crops
- The production of COâ in soil strongly depends on the availability of organic carbon (C) for microorganisms. It is obvious, that C that entered the soil recently is more easily available for microorganisms in comparison to older C. However, only very few approaches allow for a quantitative estimation of the availability of C in relation to the time it is entering the soil. We hypothesized that Î´Â¹Â³C values of COâ and of soil organic matter (SOM) after a Câ to Câ vegetation change will enable to calculate the relative availability of younger (Câ-derived) and older C (Câ-derived) sources for microorganisms. Soil COâ was sampled over one vegetation period at depths of 10, 40â50 and 60â70Â cm at three treatments: a Câ reference (wheat), a Câ/fallow (fallow after one year of maize cropping), and a Câ/Câ (two years of maize cropping). Based on the Î´Â¹Â³C of COâ purified from the admixture of atmospheric COâ by the Miller/Tans model and on the Î´Â¹Â³C values of SOM, the contributions of younger and older C sources to COâ and SOM were assessed. Depending on the soil depth and the presence of living roots, the contribution of younger C to soil COâ ranged from 16 to 50%, but that to SOM was less than 5%. By comparing the contributions of older and younger C to COâ and SOM, we found that the relative availability of organics recently introduced into the soil (Câ-derived) was about 7 times higher than the availability of C stabilized in soil for longer than one year (Câ-derived). We concluded that simultaneous analysis of the Î´Â¹Â³C values of both SOM and of COâ allows not only for the quantification of the COâ sources, but also for the estimation of the availability of soil C pools of different age for microorganisms.