[Plant community and soil nutrient of alpine meadow in different degradation stages on the Tibetan Plateau, China.]

We examined soil physical and chemical properties and plant community characteristics of four Kobresia alpine meadows at different degradation stages in Damxung County, Lhasa City, Tibet Autonomous Region, China, with the method of spatial sequence instead of time succession. The results showed that soil organic carbon, total nitrogen, available phosphorus, available potassium, ammonium, nitrate, and water content showed a decreasing trend as the degree of soil degradation increased, while pH showed an increasing trend. Plant community height, richness, diversity index and evenness index of the moderately degraded meadow were the highest. Community coverage and total biomass were the largest in undegraded meadow and the smallest in the severely degraded meadow. As the degree of meadow degradation intensifies, the biomass and proportion of Cyperaceae decreased, the biomass and proportion of legumes and weeds increased, and the biomass and proportion of Gramineae first increased and then decreased. The aboveground biomass of meadow was significantly positively correlated with soil organic carbon content, total nitrogen content, total phosphorus content, and soil water content, and significantly negatively correlated with soil pH. With the vegetation degradation in meadow, soil degradation had worsened, which ultimately manifested as a significant decline in grassland productivity.