The effects of vegetation restoration strategies and seasons on soil enzyme activities in the Karst landscapes of Yunnan, southwest China

Abstract

Soil enzymes play a vital role in biogeochemical cycling and ecosystem functions. In this study, we examined the response of six soil enzymes to changes in physicochemical properties resulting from changes in season and vegetation and geological conditions. Catalase, urease, acid phosphatase, invertase, amylase, and cellulase not only promote carbon, nitrogen, and phosphorus cycling, but also participate in the decomposition of harmful substances. Thirty-six soil samples were collected from karst and non-karst areas in two different seasons and from three different types of vegetation in Yunnan province, southwest China. Both vegetation types and season had significant effects on soil physicochemical properties and enzyme activities. In the same plot, soil water content, electrical conductivity, organic carbon, total nitrogen, and total phosphorus increased in the rainy season, indicating enhanced microbial metabolic activity. With the exception of urease activity, the remaining five enzymes showed higher activity in the rainy season. Changes in activities between the two seasons were significant in all samples. In the same season, activity levels of soil enzymes were higher in karst areas than in non-karst areas, and higher in natural forest than in artificial forests. The transformative abilities of soil elements are higher in karst areas than in non-karst areas, and higher in natural forests than in artificial forests. Correlation analysis showed that the activities of the six enzymes correlated significantly; however, soil physical and chemical indices, such as organic matter, pH, and moisture, which are essential for enzyme activity, differed by season. Redundancy analysis also revealed that the main factors influencing enzyme activity differed between the two seasons. The results from this study provide a theoretical basis for further research on the restoration of natural ecological systems in karst landscapes.