The Effects Of Grazing On The Species And Biomass Of Arbuscular Mycorrhizal Fungi In Grassland

Arbuscular mycorrhizal (AM) is mutualistic symbiont between arbuscularmycorrhizae fungi (AMF) and plant root in soil, which is a primary component inecosystem. Mycorrhizal fungi in which the plant partner supplied carbon fixedthrough photosynthesis to the fungus in return for mineral nutrients supplied by thefungus to the host plant. AMF deposited a certain amount of carbon from plantphotosynthetic, while the distribution of AMF spores and external hyphae in soil is animportant part of soil carbon pool. As one of the important grassland management,grazing can influence plant diversity directly and AMF indirectly.We conducted this study on the Songnen grassland, with four grazing treatments(cattle grazing, sheep grazing, mixed grazing with by sheep and cattle, no grazing)and two plant diversity levels (high and low). The morphological method was used tostudy the changes of AMF species and microporous membrane filtration method wasused to extract the external hyphae of AMF which is analyzed based on differentgrazing treatments and the characteristic of plant community. The main results andconclusions are present as the followings:（1） From soil sample,25species of AMF were identified，which belonging tothe following three categories, Glomus, Acaulospora and Archaeospora. The Glomusis the most, followed by G. mosseae, G. ambisporum, G. constrictum, G. etumicetunicatum were the four species, which showed a high level in species abundanceand richness. In addition, Acaulospora has four spore species and Archaeospora hasonly one spore specie.（2） Large herbivore grazing influenced AMF species. Grazing and plantdiversity influenced AMF richness, evenness and Shannon-Wiener index significantlyat plant community level. For the grass functional group, grazing decreased richnessof AMF spore. For the forb functional group, grazing had similar impacts on AMF.The AMF richness was significantly higher for the mixed grazing compared to thecattle and sheep grazing treatments.（3） Grazing affected significantly the AMF spores and hyphae density. At theplant community level, grazing decreased the AMF spores and hyphae density, andthese were at the lowest with cattle grazing. The density of AMF spores wassignificanlty reduced for grass functional groups after grazing, whereas, the density of AMF spores was significantly higher for the mixed grazing compared to the control,cattle and sheep grazing. For the forb functional group, grazing also reduced AMFspores and hyphae density. Furthermore, the results showed that a higher plantdiversity have influences on the hyphae density and the density of AMF spores wascomparatively higher with only sheep grazing at low plant diversity.In summary, grazing can influence AMF species, spore abundance and hyphaedensity. This study clarified impacts of grazing and plant diversity on AMF, whichimproved our understanding of the effects of grazing on ecosystem structure andfunction, and gave a scientific guide to grassland management.