Investigation of protease and alkaline phosphatase activities, organic carbon, nitrogen and phosphorus of Shadegan coastal soils

The aim of this study was to evaluate the changes in proteases and alkaline phosphatase activities, organic carbon content, total nitrogen and phosphorus in winter and summer time in the coastal soils of Shadegan wetland in 2019-2020. Two sampling sites including site A with dominant vegetation and site B wetlands without vegetation were selected. Soil samples were colected using ASTM standard number D2488. The results of analysis of variance showed that seasonal changes, vegetation and soil depth had a significant effect on total nitrogen, phosphorus and protease and alkaline phosphatase activity (p < 0.001). Seasonal changes did not have a significant effect on the amount of soil organic matter, while vegetation and soil depth significantly affected the amount of soil organic carbon in the coastal soil of Shadegan wetland (p < 0.001). Nutrient elements and activity of extracellular enzymes (protease and alkaline phosphatase) in vegetated soils were higher than bare soils. According to the results, the activity of protease (2.69 µmol/gh) and alkaline phosphatase (3.5 mg/PNP/gh) enzymes in topsoil (0-15 cm) with vegetation was higher in summer time compare to the  bare soils. These results  can be related to total nitrogen, phosphorus and soil organic carbon (p < 0.05) which had higher values in the summer time.  Finally, principal component analysis and Spearman correlation  confirmed a strong and positive relationship between total nitrogen, total phosphorus and soil organic carbon (p < 0.001) with the biological activity of protease and alkaline phosphatase enzymes.