The Nitrogen Fixtional Legumes And Effect Of Community In Alpine Meadow

Symbiotic nitrogen fixation of legumes with azotobacteria was a hot topic of scientific research, but less focus on alpine meadow community. Therefore, we selected four com-mon species of legumes (Astragalus polycladus. Gueldenstaedtia multiflora,Medica-go ruthenica,Oxytropis kansuensis.)in the alpine meadow as our experiment material, and studied the nitrogen-fixing ability of each specie. Meanwhile, we also design field exper-iments to study the response mechanism of community to remove of legumes functional group.The result showed as following:1) The N content in soil around the single legume plant was different. The highest N-content in soil was Astragalus polycladus, followed by Oxytropis kansuensis,Gueldenstaedtia multiflora and Medicago ruthenica. It indic-ated that there was difference of interaction between four common species of legume and rhizobia of the release of N to the soil.2)There was significant difference in vertical dimension. Between the two depth (5-10cm,10-15cm). From surface to bottom, Data showed that N-content in soil around legume root area decreased remarkably.3) there was a positive corrolation between the single legume's biomass and its root area soil N-content, so we built a liner model to explain the situation. The highest fitting was Oxytropis kansuensis.From the linear model, we also found that the strongest nitrogen fixation effect occurs when the protagonist was Medicago ruthenica, followed by Guelden-staedtia multiflora, Oxytropis kansuensis and Astragalus polycladus.4) In the removal experiment, remove the legumes functional group:The total nitrogen content of the community compared with the controlled trial was not significant. There was not significant between the total aboveground biomass and the controlled trial. However, analyse the biomass of functional groups found that the biomass of poaceae was higher th-an the controlled trial, and reached a significant level. the biomass of cyperaceae is lower than controlled trial, reached a significant level; the biomass of weed was higher than the compare, and reached a significant level.the changes in species richness compared with the controlled trial were not reached significantly different.