[Effects of land use change on soil organic carbon and its components in karst rocky desertification of southwest China].

Soil organic carbon (SOC) is the dynamic medium of carbon transfer and the main pathway of carbon transfer in the karst ecosystem. SOC and its components are the important parts in soil carbon cycling of karst ecosystem. However, few studies have focused on SOC and its components in the karst ecosystem. We analyzed the effects of land use change on the SOC content, SOC reserve (SOCS), water-soluble organic carbon (WSOC), easily oxidizable organic carbon (EOC), particu-late organic carbon (POC), and light fraction organic carbon (LFOC), and heavy fraction organic carbon (HFOC) and their distribution ratio, with six different land-use patterns [Zanthoxylum bungeanum forest (HJ), Hylocereus undulates forest (HL), mixed forest of Z. bungeanum and H. undulates (HHL), Sabina chinensis forest (YB), mixed forest of S. chinensis and Ligustrum luci-dum (YBN), and slope cropland (PD)] in Huajiang Canyon of Guanling County, Guizhou Pro-vince. Results showed that SOC and SOCS in YB, YBN and HJ were significantly higher than those in HL, HHL and PD. In the 0-20 cm soil layer, the concentrations of SOCS followed the order of HJ＞YB＞YBN＞PD＞HHL＞HL. Contents of WSOC, EOC, POC, LFOC and HFOC in YB, YBN, and HJ were all higher than those in the other three patterns. Significant positive correlations existed between SOC and each of its components (WSOC, EOC, POC, LFOC and HFOC), also between any two of those components. Z. bungeanum could be used as a priority economic species for the ecological rehabilitation of karst rocky desertification and mountain agriculture development in Southwest China. WSOC, EOC, POC, LFOC and HFOC could be used as indicators of soil organic carbon pool.