Analysis of Differences in Soil Nutrients and Enzyme Activities Between the Pure Artificial Plantation Forest of Chinese fir and the Mixed Forests of Four Tree Species

The effects of different mixed afforestation of Chinese fir on the content of nutrient in soil surface and soil enzyme activity were discussed, which could provide theoretical basis for the scientific management of the pure artificial plantation forest of Chinese fir. In this study, the mixed forests of four tree species, including Cunninghamia lanceolata+Castanopsis hystrix+Cryptomeria japonica+Castanopsis carlesii (the mixed forest 1), Cunninghamia lanceolata+Castanopsis hystrix+Fokienia hodginsii+Taxus wallichiana (the mixed forest 2), Cunninghamia lanceolata+Pinus massoniana+Mytilaria laosensis+Taxus wallichiana (the mixed forest 3), and the pure artificial plantation forest of Chinese fir were used as the research objects to analyze the differences of soil nutrients and soil enzyme activities in different stands and the relationship between them. The results showed that: Compared with the pure Chinese fir plantation forest, the soil dissolved organic nitrogen (DON) in the mixed forest was higher, and the soil microbial biomass carbon (MBC) in the mixed forest 1 and the mixed forest 3 was 37.82% and 1.84% higher than that in the pure Chinese fir plantation forest, respectively. The soil DOC∶DON in the mixed forest was significantly lower than that in the pure Chinese fir plantation forest (P＜0.05), while the soil MBC∶MBN in the mixed forest was significantly higher than that in the pure Chinese fir plantation forest (P＜0.05). The acid phosphatase (AP) activity in the mixed forest was significantly higher than that in the pure Chinese fir plantation forest (P＜0.05). The correlation analysis showed that the soil total carbon (TC), total nitrogen (TN) (P＜0.01) and DON (P＜0.05) were significantly positively correlated with the soil β-glucosidase (BG) activity and acid phosphatase (AP) activity. The research showed that: compared with the pure Chinese fir plantation forest, although the afforestation model of the mixed forest of Chinese fir could better improve the soil organic nitrogen content, microbial carbon content and soil microbial biomass carbon-nitrogen ratio during the young forest period, and then affect the soil enzyme activity, which was more conducive to improving the soil quality of the pure Chinese fir plantation forest.