The Effect Of Arbuscular Mycorrhiza Fungi In Rhizosphere Microecology Of Robinia Pseudoacacia

The function diversity of microbial community in rhizosphere soils of Robinia pseudoacacia plantation and secondary forest at different ages on ecology deterioration area of the Loess Plateau, the effect of Arbuscular Mycorrhiza (AM) fungi on microbial community, and the inoculation effect of AM fungi on R. pseudoacacia were studied in this paper. In order to reveal mechanism of AM fungi on rhizosphere microecology of R.pseudoacacia, so as to provide a scientific basis for restoration and reconstruction on ecology deterioration area of the Loess Plateau and returning farmland to forest project in Chinese Western Region. Main research results were as follows:(1) the function diversity of microbial community in rhizosphere soilsIn 8a, 15a, 23a, 30a plantation forestland, with the ages increased, the total microbial biomass, microbial activity (average well color development , AWCD) increased, the richness index(S) and Shannon index(H) increased at first and achieved peak value at 23a then gradually declined. 8a secondary forest was superior than same ages plantation in microbial biomass and function diversity. With the ages increased, the carbon utilization level increased, the Carbohydrates was always superior utilized carbon. With the ages increased, the microbial community structure and function in rhizosphere soils of R.pseudoacacia plantation existed continuity of the time, secondary forest was better than the same old plantation, being similar with the older plantation in carbon utilization.(2) the effect of AM fungi on microbial communityIn 8a, 15a, 23a, 30a plantation forestland, with the ages increased, the mycorrhizal infection rate and spore density increased at first and then declined, but the trend and range of variation were different. The mycorrhizal infection rate and spore density of 8a secondary forest were superior. The mycorrhizal infection rate and the number of nodules were significant correlation (r=0.927, P<0.05) in different forestlands. Absorbing phosphorus of AM fungi and symbiotic nitrogen fixation of rhizobium had synergistic effect, enhancing soil fertility and promoting ecology restoration on the Loess Plateau.Close relationship was present between AM fungi and microbial community in 8-15a forestlands, the total microbial biomass, richness index (S) and Shannon index (H) had a positive correlation with mycorrhizal infection rate (r=0.869, 0.975, 0.929) and spore density (r=0.955, 0.999, 0.987). It reflected that AM fungi had a positive effect on microbial biomass and function diversity, In 23-30a plantation the relationship of AM fungi and microbial community was complex, in mycorrhizal infection rate, spore density, richness index (S), Shannon index (H) 23a plantation was better than 30a plantation, but 23a plantation was worse in microbial biomass and microbial activity.(3) the inoculation effect of AM fungi on R.pseudoacaciaAM fungi could activate soil nutrient and promote plant growth through improving root activity and active root absorbing area, changing root plasma membrane permeability, increasing microbial biomass and improving soil enzyme activity. In active root absorbing area, microbial biomass and soil enzyme activity, G. mosseae treatment and G. constrictum treatment had no significant difference (Pï¹¥0.05), but in root activity and average biomass they were very significant difference (P<0.01), these indicated that the promoting growth effect of AM fungi on R.pseudoacacia was a comprehensive influence by above-ground and under-ground's synergistic effect. The inoculation effect among different AM fungi on R.pseudoacacia was different. In production practice the combination of AM fungi and host plant should be paid more attention. The combination of"suitable fungus for available tree species"was important for achieving maximized ecological benefit.