Results
Soil enzyme activities
Generally, the mean NAG and LAP enzyme activities increased from the uncultivated land to cropland to afforested lands (shrubland and woodland) with higher levels in the top soil than deep soil (Fig. 1). The seasonal patterns of NAG and LAP enzyme activities showed higher levels in summer compared to other seasons in all land use types except the cropland with lower level of NAG enzyme activity in summer at the top soil (Fig. 2). The mean specific enzyme activities for two N-hydrolyzing enzymes were significantly lower in the uncultivated soils than other land use types at both soil layers except in the shrubland of deep soil (Fig. 3). Notably, two specific enzyme activities were higher in the top soil than deep soil, but there were no significant differences in two specific enzyme activities between top soil and deep soil in the woodland (Fig. 3).