Abstract: In this paper,535 soil samples (0～20 cm) were taken from the woodland,orchard,upland,and paddy field in the hilly red soil region of south China,and the quantitative characteristics of soil organic carbon (SOC) and soil microbial biomass carbon (SMB-C) were studied.The results showed that SOC content was the highest (16.0 g·kg^-1) in paddy field and the lowest (8.4 g·kg^-1) in woodland,while SMB-C content was the highest in paddy field (830 mg·kg^-1) and the lowest in orchard (200 mg·kg^-1).There was a highly significant positive correlation (P＜0.01) between the contents of SOC and SMB-C in the four landuse types.It was suggested that the changes of SMB-C content could sensitively indicate the dynamics of SOC.The transition from woodland to orchard or cultivated land in hilly red soil region would not decrease the SOC content.

Key words: rare and endangered plants, Inner Mongolia., endangered grade, conservation priority