The effect of climate and land uses on soil microbial biomass and activities

Today, one of the major concerns in the world and Iran is land use change from forests and pastures to agricultural lands which causes soil quality mitigation and global climate change. One of the indicators of soil quality and health is the evaluation of microbial activity and the estimation of microbial biomass of the soil, which in a short time responding to management practices in different ecosystems. This research was conducted to study the effect of climate and forest, pasture and agricultural land uses on soil microbial activities and biomass in Ilam province in 2016. The impact of climate was considered with selection of two regions including Ayvan, with semi-humid climate and Ganjavan, with semi-arid climate. Three land uses including forest, pasture and agricultural land were investigated in each region. After field studies in the land uses, five soil samples were randomly taken from 0-10 and 10-30 cm depths. In laboratory, soil microbial properties including microbial biomass carbon and nitrogen, basal respiration and substrate induced respiration as well as soil organic carbon were measured. The results showed that the highest organic carbon and basal respiration were obtained in the Ayvan climate with forest ecosystem to be 42.54 and 20.72 percent, respectively. Agriculture land use in both climates had the least amount of these properties. Organic carbon, base respiration and substrate induced respiration decreased in different land use with increasing soil depth. The microbial biomass carbon and nitrogen in forest and rangeland land use in Ayvan climate were higher than Ganjun climate. The highest microbial biomass carbon (813 mg g^-1 soil) was obtained in forest land use at topsoil (0-10 cm). Soil microbial biomass decreased with increasing soil depth. Soil metabolic coefficient in subsoil (10-30 cm) was higher than topsoil (0-10 cm), and the highest metabolic coefficient of soil (0.179 percent) was observed in subsoil (10-30 cm) with agricultural land use. The lowest metabolic coefficient (0.087 percent) was observed in the soil surface (0-10 cm) with forest land use. In general, the results showed that in dry climate, by changing the land use from forests to pasture and agronomy land in dry climate decreased organic carbon and soil microbial activity. Therefore, correct land management in semi-humid and semi-arid regions can play an important role in improving soil quality and health.