Chin J Plan Ecolo ›› 2004, Vol. 28 ›› Issue (5): 657-664.DOI: 10.17521/cjpe.2004.0088

• Research Articles • Previous Articles     Next Articles

CHANGES IN SOIL LABILE ORGANIC CARBON UNDER DIFFERENT LAND USE IN THE LIUPAN MOUNTAIN FOREST ZONE

WU Jian-Guo1ZHANG Xiao-Quan2 and XU De-Ying2   

  1. (1 Research Center of Impact of Climate Change of Chinese State Environmental Protection Administration, Beijing 100012, China) (2 Institute of Forest Ecology and Protection, Chinese Academy of Forestry Science, Beijing 100091, China)
  • Received:2003-03-10 Online:2004-03-10 Published:2015-11-03
  • Contact: WU Jian-Guo

Abstract:

Soil carbon is a large component of the global carbon cycle, and the influence of land-use changes on soil carbon pools can significantly affect atmospheric CO2 concentrations. Labile soil organic carbon (LSC) is the fraction of soil organic matter that is most sensitive to changes in land-use. Over the last several centuries, extensive areas of native vegetation in the Liupan Mountain Forest Zone have been converted to croplands and rangelands and, in last several decades, some of these former croplands and rangelands have returned to forests. The impacts of these land-use changes on soil organic carbon (SOC) are unclear. In order to assess the impacts of land-use change on LSC, we compared the LSC concentrations in adjacent plots of secondary forest (i.e. dominated by Quercus liaotungensis, Populus davidiana, or brushwood), cropland, rangeland, and 13, 18, and 25-year old larch (Larix principis-rupprechtii) plantations that were planted on former croplands and rangelands. All plots were the same elevation, exposure and soil type. The LSC concentrations were determined using a KMnO4 (333 mmol•L-1) oxidation technique. It was found that the mean content of LSC in 0-110 cm deep soil layer was 60% lower under cropland (0.605 gC•kg-1) and 36% lower in rangeland (0.973 gC•kg-1) than under the secondary forest (1.612, 1.68 and 1.325 gC•kg-1 for the brushwood, Populus davidiana and Quercus liaotungensis forests, respectively). LSC was 129% and 29% higher under the plantations (1.127, 1.520 and 1.523 gC•kg-1 for the 13, 18 and 25-year old Larix principis-rupprechtii plantations, respectively) than under the cropland and rangeland respectively. The change of LSC content with soil depth was greater under the secondary forest and plantation than under the cropland or rangeland. The difference of LSC content between secondary forest and rangeland or cropland was greater in the 0-70 cm depth than in the 70-90 cm deep soil layer, whereas differences in LSC content between the plantations and rangeland or cropland was greater in the 0-50 cm than 50-110 cm soil layer. The mean fraction of LSC in the 0-110 cm soil layer was 11% lower under cropland (0.087) and 4% lower under rangeland (0.094) than under the secondary forest (0.098, 0.099 and 0.099 for brushwood, Populus davidiana and Quercus liaotungensis forests, respectively). The mean LSC fraction was 13.3% and 5.3% higher under the plantations (0.103%, 0.093% and 0.101% for the 13, 18 and 25-year old Larix principis-rupprechtii plantations, respectively) than under the cropland and rangeland, respectively. The change in the LSC fraction with soil depth under cropland was greater than for all other land use types. The difference in the LSC fraction between secondary forests and rangeland or cropland was greater in the 0-20 cm and 70-110 cm than the 20-70 cm soil layer, whereas the difference in the LSC fraction between the plantation and rangeland or cropland was greater in the 0-110 cm soil layer. In general, the differences in LSC among the different land use types and changes with depth were greater for the content of LSC than the LSC fraction. Differences in LSC among the different land use types are attributed to differences in the inputs, stabilization and quality of soil organic matter, and the distribution of roots among the different land uses. The results of this study indicate that the LSC content and fraction will decline if natural secondary forest are converted to cropland or rangeland but will increase with afforestation of croplands or rangelands. In addition, the distribution of the content or fraction of LSC within the soil profile will change with changes in land use, but the change in the LSC fraction is smaller than the chaoge of the LSC content.