Evaluation of soil enzyme activities as soil biological activity indicators in desert-oasis transition zone soils in China

Abstract

The seasonal and spatial variations (desert, desert-oasis, and oasis) in some enzyme activities (urease, alkaline phosphatase, nitrate reductase, dehydrogenase, and catalase) in the 0–20 cm and 20–40 cm soil layers were evaluated along a typical desert-oasis transition zone in the Shule River basin in China. The results showed that there was a significant positive correlation of soil urease, alkaline phosphatase, dehydrogenase, and catalase activities with vegetation coverage and available phosphorus while they had a negative correlation with soil pH and EC. Nitrate reductase activity was positively correlated with soil pH and EC but was negatively correlated with elevation and vegetation coverage. According to the redundancy analysis, environmental factors (elevation, vegetation coverage, soil moisture contents, pH, EC, OM, AP and AK) in this study explained 89.8% of the soil enzymatic activity variations when combined (p < 0.01). The Monte Carlo simulation showed that the order of importance of environmental factors on soil enzyme activities was as follows: vegetation coverage (42.5%) > elevation (38.0%) > EC (30.7%) > AP (18.1%) > pH (15.4%). Accordingly, catalase activity exhibited sensitivity to changes in land use intensity and no seasonal variation, suggesting that it is the soil biological activity indicator best suited for measuring existing conditions and potential changes in the desert-oasis transition zone soils.