The linkage between vegetation and soil nutrients and their variation under different grazing intensities in an alpine meadow on the eastern Qinghai-Tibetan Plateau

The grassland degradation caused by overgrazing is the result of imbalance of energy flow and material cycle under grazing pressure in the ecosystem, and numerous ecological restoration and ecological engineering techniques widely used to restore some ecosystem. However, little research known focused on the relationship (energy flow and material cycle) between plant and soil under different grazing intensity, especially at the rhizosphere which is the most powerful area of plant and soil interaction. In this research we conducted a 5-year grazing experiment including 4 different grazing intensities (no grazing, UG; light grazing, LG; moderate grazing, MG; and heavy grazing, HG) in an alpine meadow on the northeastern margin of Qinghai-Tibetan Plateau (QTP). Plants and soil materials were sampled in July 2015, and to examine the nutrients concentration and ecological stoichiometric of vegetation and soil, the soil microbial biomass and activity, as well as their relationship with vegetation and soil characteristics. We found that grazing increased vegetation and soil nutrient concentrations and increased the ratio of microbial biomass carbon (MBC) to microbial biomass nitrogen (MBC), but the grazing intensity did not significantly influence the nutrients enrichment ratio of rhizosphere soil. There was significant relationship between total carbon (TC) concentration of vegetation and soil, and between vegetation total phosphorus (TP) and soil PO43--P concentration. These results suggested that vegetation and soil nutrient concentrations respond differently to the grazing intensity. Coupling relationship exists in specific nutrients of vegetation and soil and rhizosphere is a powerful tool to understanding the linkage between plant and soil.