Statistics
Soil N-hydrolyzing enzyme activities in soil were normalized to SON concentration (enzyme: SON) to analyze the specific enzyme activities. Multiple-way Analysis of Variance (ANOVA) was used to test the statistical significance of land use types, seasons, depths and their interactive effects on soil variables (two N-hydrolyzing enzyme activities). One-way ANOVA with Tukey’s HSD test was used to further test the statistical significance of land use types, seasons, depths on soil enzyme activities, respectively. Analysis for all of the data was carried out using IBM SPSS Statistics 21.0 software (Armonk, NY, USA). The Pearson correlation coefficients using IBM SPSS Statistics 21.0 and redundancy analysis (RDA) using Canoco5.0 were performed to quantify the correlations between soil enzyme activities and soil variables. The significance level was established at p < 0.05. Soil C-, N- and P-hydrolyzing enzyme activities were loge-transformed prior to stoichiometric analyses following the conventions of stoichiometric studies and to better achieve normality (Sterner and Elser 2002; Sinsabaugh et al., 2009)