Different characteristics of vegetation and soil properties along degraded gradients of alpine grasslands in the Qinghai-Tibet Plateau

Alpine grassland is an important component of the Tibetan Plateau. The degradation of these grasslands affects regional sustainable development. The mechanisms of linkage between soil properties and vegetation traits to the succession process of grassland degradation are still unclear. In the present study, we investigated the correlation of different vegetation characteristics and soil properties with degree of degradation (non-degraded to heavily degraded) of grasslands from across the Tibetan Plateau. The results showed that the aboveground and belowground biomass and the soil properties declined along the degradation gradient. For instance, in heavily degraded grassland, aboveground biomass, below-ground biomass, species richness and species evenness were lower by 42.44%, 60.64%, 21.08% and 8.36%, respectively, compared to non-degraded grasslands. Soil moisture content, organic carbon, total nitrogen and total phosphorus in heavily degraded grasslands were also lower by 33.57%, 45.75%, 22.70% and 11.23%, respectively, compared to non-degraded grasslands. The soil bulk density was 12.12% greater in heavily degraded grasslands than in non-degraded grasslands. In terms of response ratio, we found that vegetation biomass (aboveground biomass and belowground biomass) was positively related with soil properties (organic carbon, total nitrogen and total phosphorus) (P<0.05). The findings indicated that vegetation productivity and soil properties interacted with each other in the process of grassland degradation. In addition, the carbon content loss was more serious than nitrogen and phosphorus content loss.