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.