Soil carbon and nitrogen transformed enzyme activities in continuously cultivated Chinese fir (Cunninghamia lanceolate) plantations and their correlations with soil physicochemical factors

This study aims to investigate the seasonal changes of soil carbon and nitrogen-transformed enzyme activities and their driving factors in successive rotations of subtropical Chinese Fir（Cunninghamia lanceolate） plantation. The results would provide basis for assessing nutrient cycling and soil quality in forest. Through canonical redundancy analysis（RDA） the relationships between soil physical properties, nutrient conditions, and enzyme activities were analyzed in different generations of Chinese fir plantation（FRP, SRP, TRP） and Castanopsis Kawakamii forest（NF） in Fujian province, China. A significant decrease of soil pH was observed in Chinese fir plantation compared with NF, but no significant changes were found between FRP, SRP, and TRP. In December, there was no significant difference on soil total carbon and nitrogen among different generations of Chinese fir plantation, and the SRP and TRP were significantly higher than the NF（P < 0.05）. In June, soil total carbon of TRP was significantly higher than