Comparison Of Soil And Microbial Biomass Carbon,nitrogen And Phosphorus In Pure And Mixed Pinus Sylvestris Var.mongolica Plantations

In order to provide suggestions for the construction and sustainable management of Pinus sylvestris var.mongolica protective plantation in Horqin sandy land,we analyzed seasonal dynamics and vertical distribution of soil and microbial biomass C,N and P,and then compared the differences in soil nutrient transformation among P.sylvestris var.mongolica pure plantation,P.sylvestris var.mongolica × Maackia.amurensis mixed plantation and P.sylvestris var.mongolica × Ulmus pumila mixed plantation.The results showed that compared with the national average,lower the contents of soil C,N,and P and higher C/N,soil microbial biomass C,N and P entropy were found in P.sylvestris var.mongolica pure and mixed plantations.Generally,with the seasonal change,the organic C content increased at 0-20 cm soil layer but decreased at 20-40 cm and 40-60 cm soil layer,and the contents of total N,available P,soil microbial biomass N increased,while the contents of total P and soil microbial biomass C decreased,the available N content increased in 0-20 cm and 40-60 cm soil layer but decreased at 20-40 cm soil layer in P.sylvestris var.mongolica pure plantation.In P.sylvestris var.mongolica × M.amurensis mixed plantation,the soil C content decreased,the soil total N content at 0-20 cm soil layer unchanged but increased at 20-40 cm and 40-60 cm soil layer,while the contents of available N,soil microbial biomass N and P decreased,the total P content decreased at 0-20 cm and 40-60 cm soil layer but increased at 20-40 cm soil layer,the available P content increased,and the soil microbial biomass C content rose at 0-20 cm soil layer but decreased at 20-40 cm and 40-60 cm soil layer.In P.sylvestris var.mongolica ×U.pumila mixed plantation,the organic C content increased at 0-20 cm soil layer but significantly unchanged at 20-40 cm and 40-60 cm soil layer,the total N content significantly unchanged at 0-20 cm soil layer but increased at 20-40 cm and 40-60 cm soil layers,while the contents of available N,total P,soil microbial biomass N and P decreased,the available P content increased,the microbial biomass C content increased at 0-20 cm and 40-60 cm soil layers.According to the principal component analysis,the scores of P.sylvestris var.mongolica pure and mixed plantations were ranked as follows: P.sylvestris var.mongolica × M.amurensis mixed plantation > P.sylvestris var.mongolica × U.pumila mixed plantation > P.sylvestris var.mongolica pure plantation.Therefore,the soil improvement effect of the P.sylvestris var.mongolica × M.amurensis mixed plantation was the best.