3.3. Variation of soil enzyme activities in different vegetation types
The type of vegetation significantly affected soil amylase, urease, and sucrase activities (Fig. 3). There were no significant differences in soil catalase activity among the four vegetation types. However, a two-way ANOVA test revealed a significant association between soil depth and vegetation type on catalase activity (Table 3). For the 0-20 cm soil layer, the amylase activity in GL vegetation was significantly higher than that of the other three vegetation types (Fig. 3A); the urease activity of XS vegetation was significantly higher than that of HR, CK, and GL by 58.75, 69.04, and 48.49 mg/g, respectively (Fig. 3C); soil sucrase activity in GL vegetation was significantly higher than HR and CK by 110.23 and 423.35 mg/g, respectively, but no significant difference was observed in XS vegetation (Fig. 3D). In the 20-40 cm soil layer, HR amylase activity displayed significant differences with CK, and displayed no significant differences with XS and GL. The CK amylase activity was significantly lower than the other three vegetation types. The soil urease activity in the 20-40 cm layer of XS vegetation was significantly higher than that of the other three types of vegetation. As soil depth increased, vegetation soil catalase and sucrase activities increased (except for CK). Soil enzyme activity under other vegetation types was greater in the upper layers than in the lower layers. A two-way ANOVA test demonstrated extremely significant relationships between soil depth and vegetation type on enzyme activity (amylase, urease, sucrase) in all samples studied (Table 3).