Impact of different land use on physical, chemical and biological soil properties in the Qalek forest Qhaemshahr city

The destruction of natural ecosystems and conversion to other land uses caused considerable changes in the soil properties. Deforestation leads to adverse ecological conditions including the reduction of biodiversity and soil quality. The results of several studies around the world indicated that deforestation can reduce soil quality by decreasing organic matter, microbial respiration, aggregate stability, hydraulic conductivity and increasing bulk density. The present study aimed to investigate the effect of different land use on soil productivity characteristics in a part of Ghaemshahr, located in Mazandaran province.
To do the present investigation, four land uses were considered, included: Natural forest, recreation forest, paddy field and citrus field. The soil sampling was done by using 10 plots (20×20m) at each land use, which have been selected by randomly systematic method (50×75m). Then, soil samples were collected from the center of each plot at 0-10cm depth by using coring method (8cm diameter). The soil moisture, soil texture, bulk density, pH, EC, total N, available K and P, NO-3 and NH concentration were measured by using conventional analysis methods in laboratory. Also, net N mineralization, net ammonification rate and net nitrification were calculated. One-way analysis of variance (ANOVA) and Duncan test were used in order to test significantly differences and comparing the mean of parameters among different land uses, respectively.
Our results showed that there were considerable differences in physical, chemical and biological soil properties between different land uses. The higher amount of soil moisture (36/47), organic carbon (5/1), total nitrogen (0/46), C/N ratio were observed in recreation forest and the lower amount of organic carbon (1/68), potassium (260/54) and C/N (7/71) ratio were observed in rice field. The lower input of organic matter into the soil (due to the loss of natural forest cover), destruction of aggregates (because of the plow process) and the lack of physical protection of soil organic matter caused to decrease of amount of soil organic carbon and total nitrogen in rice field. Ammonium-N concentration showed no significant difference between different sites for both sampling date (September and October), but the highest ammonium concentration was found in forest lands and its lowest concentration was observed in paddy field and citrus field. The higher ammonium concentrations may be related to higher rates of N mineralization in soil of both forest land uses (recreation forest and natural forest).Increasing temperature, water content, pH and labile sources of C and N (for microbial communities) can be lead to increase N mineralization rate and microbial activity. Also, results showed that net N mineralization and net nitrification were occurred just in the soil of paddy field and recreation forest.
According to our findings, N dynamics can be influenced by changing of forest land use. Thus, total N and its mineral forms can be used as the key indexes to evaluating the effects of land management on soil quality.