Soil microbial biomass characteristics in response to vegetation restoration on abandoned lands in Yangou watershed of China

Taking the Yangou watershed located in the hilly-gully region of the Loess Plateau as an example, the responses of soil microbial biomass characteristics to vegetation restoration on abandoned lands were studied. The results showed that with an increase of vegetation restoration years, vegetation coverage, vegetation abundance, and amount of species increased at the beginning of vegetation restoration(4-16 years), then decreased(16-29 or 16-55 years), and later increased again(after 30 or 55 years). Respiration rate and microbial biomass of topsoil(0-5 cm)significantly increased compared to cropland with topsoil respiration rate, microbial biomass C, microbial biomass N and microbial biomass P increased by 31.61%-360.75%, 15.19%-512.81%，122.91%-697.15% and 193.5%-2068.17%, respectively. At the early stages of vegetation restoration(0-29 years), topsoil respiration rate increased with an increase of vegetation restoration years, then decreased at 30-55 years of vegetation restoration, and then increased again after 55 years of vegetation restoration. With vegetation succession, the changing tendency of topsoil microbial biomass C, N, and P were similar to that of soil respiration rate. Soil respiration rates, soil respiratory quotients, soil microbial biomass C, N, and P in different restoration years showed significantly different except in 8 and 16 years. Topsoil respiration rate was significantly correlated with soil microbial biomass N and P, but soil respiratory quotient was not significantly correlated with soil respiration rate, soil microbial biomass C, N, and P.