Response of microbial community functional diversity in the rhizosphere of Caragana microphylla to environmental change

Functiona1 diversity of soil microbia1 communities in rhizosphere of Caragana microphylla,a dominant shrubby leguminous species in the Inner Mongolia Grassland Ecosystem,was examined using the Biolog method to evaluate the effects of environmental changes in atmospheric CO 2 concentration,soil nitrogen level and water level on soil microbia1 community.The results showed that total amount of carbon sources utilized by microbes in rhizosphere of C.microphylla increased with the incubation time.The main types of carbon sources utilized were polymers,carbohydrates and amino acids.Principal Component Analysis indicated that microbial community functional diversity varied significantly among 8 treatment groups.Fourteen categories of carbon sources were significantly related to the principal component 1,which belonged to polymers,carbohydrates,amino acids,and carboxylic acids.Elevated CO 2 significantly increased the value of average well colour development(AWCD),richness index and Shannon evenness.Under nitrogen ad