Abstract: Taking  5-, 10-, 15-, and 20 years old poplar (Populus euramericana cv. “N 3016”) shelterbelts in Jianping County, Liaoning Province as test objects, the effects of establishing shelterbelts on the farmland soil microbial biomass carbon and nitrogen, and microbial activity were evaluated. After the establishment of shelterbelts, the concentrations of organic carbon and total nitrogen, the microbial biomass carbon and nitrogen, and the basal respiration in 0〖KG-*2〗-〖KG-*7〗15 cm soil layer increased after an initial decrease, being reached or exceeded the levels of the control after 20 years afforestation. The metabolic quotient increased significantly after 5 years afforestation, but decreased with increasing stand age. All the results suggested that under the effects of shelterbelt establishment, farmland soil microbial biomass and activity had obvious change.

Key words: metabolic quotient, farmland afforestation, land cover, soil organic carbon, soil microbial quotient, cyanobacterial toxin, lymphocyte, fish, apoptosis, mitochondria.