Abstract
Soil labile organic carbon (C) oxidation drives the flux of carbon dioxide (CO2) between soils and the atmosphere. However, the impact of grazing management and the contribution soil aggregate size classes (ASCs) to labile organic C from grassland soils is unclear. We evaluated the effects of grazing intensity and soil ASC on the soil labile organic C, including CO2 production, microbial biomass C, and dissolved organic C and nitrogen (N) mineralization in topsoils (0–10 cm) in Inner Mongolia, Northern China. Soil samples were separated into ASCs of 0–630 μm [fine ASC (fASC)], 630–2000 μm [medium ASC (mASC)] and >2000 μm [coarse ASC (cASC)]. The results showed that heavy grazing (HG) and continuous grazing (CG) increased soil labile organic C significantly compared to an ungrazed site since 1999 (UG99) and an ungrazed site since 1979 (UG79). For winter grazing site (WG), no significant differences were found. CO2 production was highest in cASC, while lowest in fASC. Microbial biomass C and dissolved organic C showed the highest values in mASC and were significantly lower in fASC. Grazing increased N mineralization in bulk soils, while it exhibited complex effects in the three ASCs. The results suggest that the rate of C mineralization was related to the rate of N accumulation. To reduce CO2 emission and nutrient loss, and to improve soil quality and productivity, a grazing system with moderate intensity is suggested.
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Acknowledgements
The authors would like to thank Yueqin Cheng (ISC-CAS), Angelika Kölbl, Greetje Pronk, and Olivia Kreyling (TU München) for laboratory work, Tabea Dietz and Sigrid Hiesch (CAU TU München) for determination of NH +4 and NO -3 concentration. This study was funded by the Deutsche Forschungsgemeinschaft (DFG) within the MAGIM project (Forschergruppe 536 MAGIM — Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate).
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Wu, H., Wiesmeier, M., Yu, Q. et al. Labile organic C and N mineralization of soil aggregate size classes in semiarid grasslands as affected by grazing management. Biol Fertil Soils 48, 305–313 (2012). https://doi.org/10.1007/s00374-011-0627-4
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DOI: https://doi.org/10.1007/s00374-011-0627-4