Effect of Soil Depth and Altitude on the Activity of Different Enzymes in Forest Soils of Arasbaran Region

Soil enzymes are considered as the effective indicators of soil quality. In the present study, the activity of some soil enzymes, including β-glucosidase, urease, cellulase, arylsulfatase, dehydrogenase, and acidic and alkaline phosphatase was investigated in Arasbaran forest soils affected by two factors of altitude and soil depth. For this purpose, a factorial experiment was conducted using a randomized complete block design and three replications. Enzyme activity was measured in soil samples taken from different soil depths (0–20, 20–40, 40–60, 60–80, and 80–100 cm) at various altitudes (0–600, 600–1200, 1200–1800, and 1800–2400 m) on a northern aspect. The results showed significant effects of soil depth, and altitude on the activity of the enzymes studied, but the reaction of different enzymes to these factors was not the same. The highest activity of urease, β-glucosidase, cellulase, arylsulfatase, and acidic and alkaline phosphatases was measured at the surface layer (0–20 cm) of the soils, which on average decreased by 50, 81, 71, 71, 59, and 66% as soil depth increased, respectively. However, dehydrogenase activity increased by 15 to 43 times with increasing soil depth. Additionally, with the increase in altitude from 0–600 to 1800–2400 m, while the activity of urease, arylsulfatase, and β-glucosidase increased on average by 1.15, 1.4, and 1.19 times, the activity of cellulase, and acidic and alkaline phosphatases decreased by 26, 10.4, and 9.6%, respectively. But, the effect of altitude on the dehydrogenase activity was not significant. The results also showed a significant positive correlation (P ≤ 0.01) between organic carbon and microbial biomass carbon, and the activity of all studied enzymes except dehydrogenase. Findings of this study reveal how the activity of different soil enzymes changes with two factors of soil depth and altitude.