Labile organic C and N mineralization of soil aggregate size classes in semiarid grasslands as affected by grazing management

Honghui Wu, Martin Wiesmeier, Qiang Yu, Markus Steffens, Xinguo Han, Ingrid Kögel-Knabner

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

Soil labile organic carbon (C) oxidation drives the flux of carbon dioxide (CO 2) 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 CO 2 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. CO 2 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 CO 2 emission and nutrient loss, and to improve soil quality and productivity, a grazing system with moderate intensity is suggested.

Original languageEnglish
Pages (from-to)305-313
Number of pages9
JournalBiology and Fertility of Soils
Volume48
Issue number3
DOIs
StatePublished - Apr 2012

Keywords

  • Dissolved organic carbon
  • Inner Mongolia
  • Microbial biomass carbon
  • Semiarid grassland
  • Soil organic carbon

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