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Background and aims: Over-grazing have significantly altered above- and belowground functions in terrestrial ecosystem. However, the influence of grazing intensity on plant-soil stoichiometric relations in alpine ecosystems remains unclear. Methods: We investigated the responses of plant-soil nutrient stoichiometric relationships to four grazing intensities (un-grazing (UG), light grazing (LG), moderate grazing (MG) and heavy grazing (HG)) in an alpine meadow on the eastern Tibetan Plateau. We measured carbon (C), nitrogen (N), phosphorus (P) and potassium (K) concentrations and their ratios in plants and soils in the peak growing season after three years of yak-grazing. Results: Compared to UG and LG plots, heavier grazing intensity at community levels and taxonomic groups decreased plant C and K concentrations by 7.6–10.5% and 17.6–21.3%, respectively, while grazing did not significantly influence plant N and P concentrations. Grazing intensity altered plant C:N and C:P ratios but not C:K and N:P ratios. By contrast, grazing intensity had no significant effects on soil nutrients and stoichiometry. Thus, the differential responses of plant and soil nutrients to grazing intensity caused that plants were more sensitive to grazing than soils. Conclusions: Our results confirm that grazing intensity has differential effects on plant and soil nutrients, implying that plant nutrients do not covary with soil nutrients under changing grazing intensity and challenging the past positive relations between plant and soil nutrients. Further long-term grazing experiments are required to understand the drivers of grazing effect on plant-soil nutrient interactions. [ABSTRACT FROM AUTHOR]

This paper provides information about the distribution, structure, and ecology of the world's largest alpine ecosystem, the Kobresia pygmaea pastures in the southeastern Tibetan plateau. The environmental importance of these Cyperaceae mats derives from the extremely firm turf, which protects large surfaces against erosion, including the headwaters of the Huang He, Yangtze, Mekong, Salween, and Brahmaputra. The emphasis of the present article is on the climate-driven evolution and recent dynamics of these mats under the grazing impact of small mammals and livestock. Considering pedological analyses, radiocarbon datings, and results from exclosure experiments, we hypothesize that the majority of K. pygmaea mats are human-induced and replace forests, scrub, and taller grasslands. At present, the carrying capacity is increasingly exceeded, and reinforced settlement of nomads threatens this ecosystem especially in its drier part, where small mammals become strong competitors with livestock and the removal of the turf is irreversible. Examples of rehabilitation measures are given. [ABSTRACT FROM AUTHOR]