Abstract: 【Objective】Changes in soil biological and biochemical properties under different landuse patterns in subtropical region of China were investigated for providing scientific instruction to develop rational measures for cultivation and fertilization management. 【Method】Landuse patterns were selected in a small watershed of subtropical region of China for taking and analysing soil samples to compare the changes in soil organic carbon and nutrient contents, mineralization of soil organic carbon, and soil microbial biomass and community functional diversity. 【Result】Soil organic carbon and total nitrogen contents, microbial biomass C and N, and respiration intensity under different landuse patterns were changed in following order of paddy fields (and vegetable farming) > bamboo stands > fruit trees (and upland), in which paddy field (and vegetable farming) were 76.4%, 80.8% (0~15cm) and 59.8%, 67.3% (15~30cm) higher soil organic carbon and total nitrogen contents than and 6.36, 3.63, 3.20 times soil microbial biomass C, N, respiration intensity of that in fruit trees (and upland), respectively. Soil microbial metabolic quotient was fruit trees (and upland) > forestry land > paddy field, in which metabolic quotient in paddy soil was only 47.7% of that in fruit trees (and upland) soil. Amount and rate of soil organic carbon mineralization during incubation were paddy field > bamboo stands > fruit trees (and upland). Soil bacteria population was paddy field > fruit trees (and upland) > forestry land, while no significant difference existed in fungi and actinomycetes populations. BIOLOG analysis indicated a changing order of paddy field > fruit trees (and upland) > forestry land in value of average well cell development (AWCD) and Shannon, Simpson, McIntosh diversity indexes representing carbon utilization of microorganism. Results also showed that paddy field conversion to vegetable farming for 5 years, which was accompanied by large amount of phosphate fertilizer application, dramatic increase of soil available phosphorus content while insignificant changes in soil organic carbon and total nitrogen content, would caused a decrease of 53%, 41.5%, 41.3% in soil microbial biomass C, N, respiration intensity respectively, an increase of 23.6% in metabolic quotient, and a decrease in soil organic carbon mineralization rate. Soil bacteria and actinomycetes populations were increased slightly, fungi population increased dramatically, and functional diversity indexes of soil microbial community decreased significantly. 【Conclusion】It was suggested that soil biological and biochemical properties were quite different under landuse patterns. Soil organic carbon and nutrient contents, mineralization of organic carbon and functional diversity of microbial community in paddy field were higher than that in upland and forestry land in subtropical region of China. While, overuse of chemical fertilizers for a paddy field with high fertility would cause decrease of soil biological properties and biochemical function, resulted in deterioration of soil biological quality.

Key words: Land use patterns, Transformation of soil organic carbon, Functional diversity of soil microbial community