Abstract: Understanding changes in soil microbial biomass and enzyme activities with stand development is crucial for post-afforestation management. Here, we examined the changes in microbial biomass carbon, nitrogen, extracellular enzyme activities and their association with environmental factors in different soil layers (0-10, 10-20 and 20-40 cm) in Cunninghamia lanceolata plantations of different stand ages (5, 8, 21, 27 and 40 years old) in the southern Wuyi Mountains, China. The results showed that soil microbial biomass carbon and nitrogen increased significantly with stand development. Soil enzyme activities showed a unimodal trend. Specifically, cellulose hydrolase, glucosidase, β-N-acetylglucosaminidase and acid phosphatase activities peaked in 8 years old stand, whereas polyphenol oxidase and peroxidase activities peaked in 21 years old stand. Soil microbial biomass carbon and nitrogen and enzyme activities decreased with increasing soil depth across all stand ages. Results of redundancy analysis revealed that soil moisture, total nitrogen, available phosphorus, and soluble organic nitrogen contents significantly influenced soil microbial biomass and soil hydrolytic enzyme activities, while oxidative enzyme activities were primarily regulated by soil moisture and available potassium. In conclusion, soil nutrient contents were the primary drivers of the variations in enzyme activities across different stand stages. When evaluating the impacts of nutrients on soil microbial properties and enzyme activities during the stand development of C. lanceolata plantations, the important role of available potassium on oxidative enzyme activities cannot be ignored.

Key words: stand development, soil depth, soil microorganisms, soil extracellular enzyme, environmental factor