Land-use impact on soil carbon and nitrogen sequestration in typical steppe ecosystems, Inner Mongolia

Abstract

To explore the optimal land-use for soil carbon (C) sequestration in Inner Mongolian grasslands, we investigated C and nitrogen (N) storage in soil and soil fractions in 8 floristically and topographically similar sites which subjected to different land-use types (free-grazing, grazing exclusion, mowing, winter grazing, and reclamation). Compared with free-grazing grasslands, C and N storage in the 0-50 cm layer increased by 18.3% (15.5 Mg C ha−1) and 9.3% (0.8 Mg N ha−1) after 10-yr of grazing exclusion, respectively, and 21.9% (18.5 Mg C ha−1) and 11.5% (0.9 Mg N ha−1) after 30-yr grazing exclusion, respectively. Similarly, soil C and N storage increased by 15.3% (12.9 Mg C ha−1) and 10.2% (0.8 Mg N ha−1) after 10-yr mowing, respectively, and 19.2% (16.2 Mg C ha−1) and 7.1% (0.6 Mg N ha−1) after 26-yr mowing, respectively. In contrast, soil C and N storage declined by 10.6% (9.0 Mg C ha−1) and 11.4% (0.9 Mg N ha−1) after 49-yr reclamation, respectively. Moreover, increases in C and N storage mainly occurred in sand and silt fractions in the 0-10 cm soil layer with grazing exclusion and mowing. Our findings provided evidence that Inner Mongolian grasslands have the capacity to sequester C and N in soil with improved management practices, which were in the order: grazing exclusion > mowing > winter grazing > reclamation.