The Effect Of Land Management Intensification On Soil Property And Microbial Community

Although land use intensification(LUI)has been recognized as a major contributor to global plant diversity loss,our understanding of its influence on soil physical and chemical properties and soil microbial diversity and community composition across multiple taxonomic levels and soil depths remains unclear.Here we sampled soils of three layers(0-10 cm,10-20 cm,20-40 cm)from a full spectrum of LUI including unmanaged broadleaf,lightly managed broadleaf-dominated and bamboo-dominated,moderately managed pure bamboo forests,and grasslands recovered from intensively managed rice fields,all of which originated from native broadleaf forests under similar climate and soil conditions in subtropical China.Our research questions were:(1)how soil physical and chemical properties including soil carbon,nitrogen and phosphorus as well as their stoichiometry across soil layers responded to a gradient of LUI;(2)how soil fungi/bacterial ratio,bacterial fungal a-diversity and their community composition at three taxonomic levels across soil layers changed along LUI.We hypothesized that:(1)soil carbon,nitrogen and phosphorus would respond differently to LUI as a result of the balance of biomass extraction and fertilization;(2)soil microbial diversity would peak at intermediate LUI;(3)soil microbial composition would shift orderly with LUI.Our results show that:(1)soil pH,soil organic carbon,total nitrogen,and N:P did not change significantly with LUI,while soil bulk density and total P were higher in grasslands and C:N and C:P were higher in broadleaf and broadleaf dominated forests.Soil bulk density and pH increased,while soil organic carbon,total nitrogen,total phosphorus,C:P and N:P decreased with soil depth;(2)multivariate analysis indicated that land use types were well separated based on soil physical and chemical properties with the soil of native forests being most distinctly different from those grasslands,and aboveground stand characteristics strongly influenced soil properties;(3)and the ratio of available to total were both affected by plant composition and plant identity,especially the composition of soil property more affected by plant composition;(4)both bacterial and fungal operational taxonomic unit(OTU)richness was significantly higher in lightly and moderately managed forests than unmanaged forests and grasslands at all three sampled soil depths,while neither bacterial nor fungal richness at the phylum and family levels changed with land use type;(5)Across land use types,OTU richness increased with bamboo proportion and tree species richness,which were better predictors than soil physical and chemical properties.(6)As hypothesized,the community compositions of bacteria and fungi at the family and OTU levels shifted orderly with LUI and were influenced by both aboveground and soil properties.Our results highlight strong influences of LUI on soil properties and nonlinear responses of microbial diversity and an orderly shift of microbial composition to a full spectrum of LUI.