Effects of Active Soil Organic Carbon on the Processes of Karst Rocky Desertification

The research area is a typical karst catchment subject to rocky desertification in Huajiang Gorge,Guizhou Province.One representative soil sample was collected in each plot of strong,medium,slight,or latent desertification grade.The research focused on active soil organic carbon(ASOC) in the processes of rocky desertification.Results elucidated that the characteristics such as soil microbial biomass carbon(SMBC),light fraction organic carbon(LFOC),mineralizable carbon(MC),and microbial quotient(qSMBC) had a decreasing trend,while microbial metabolic quotient(qCO2) had an increasing trend,which acted in accord with the direction of rocky desertification.The above biological characteristics could embody the essence of soil degradation in the processes of rocky desertification.The turn over speed of active SOC in reclamation sequence was higher than that in wood chopping sequence,while the decreased speed of SMBC in reclamation sequence was faster than that in wood chopping sequence.With the long period of accumulation,the wood chopping sequence kept higher SOC content than the reclamation sequence even with high amount of biological return.The biological characteristics such as SMBC,LFOC,MC,labile organic carbon(LOC),qSMBC,and qCO2 were influenced both by anthropogenic disturbing ways and by the vegetation productivity and could embody the development direction of soil quality.Meanwhile,they were sensitive indexes of estimating soil quality degradation and restoration in the processes of karst rocky desertification.