LAUSR

Riparian forests are important ecosystems especially in arid zones but no information is available about soil enzyme activity in this ecosystem. Therefore, the objectives of this study were to explore some soil enzyme activities and investigate which soil physico-chemical factors affect these soil enzyme activities in riparian forests the most. Tamarix arceuthoides and Populus euphratica that stands close to one another were selected and soil samples were taken from depths of 0–10, 10–20, 20–30, and 30–40 cm. Analysis of variance was performed to detect significant differences in soil enzyme activity and physico-chemical properties between the studied soil depths. Pearson correlation coefficients were also calculated to determine the correlation between soil enzyme activity and soil physico-chemical properties. The results indicate that soil acid and alkaline phosphatase in T. arceuthoides and P. euphratica stands had the highest and lowest values at depths of 0–10 and 30–40 cm, respectively. Soil urease, dehydrogenase, and β-glucosidase had similar results with higher activity in the topsoil compared to the subsoil in both studied stands. Monte Carlo permutation test results of RDA (redundancy analysis) indicated that the most important soil factors to influence enzyme activities in the T. arceuthoides stand are soil nitrogen, organic carbon, and potassium; while the most important factors in the P. euphratica stand are soil nitrogen, organic carbon, moisture, and potassium. Soil moisture is a key factor influencing enzyme activity in the P. euphratica stand. Soil dehydrogenase and β-glucosidase activity in the P. euphratica stand were greater compared to the T. arceuthoides stand. This might indicate greater soil biological activity in the P. euphratica stand compared to the T. arceuthoides stand. Overall, soil moisture, organic matter, and plant species are the key factors effecting soil enzyme activity in riparian forest.