Plant-soil Feedback Effects During Natural Restoration And Succession Of The Sub-Alpine Meadow

Plants alter abiotic and biotic soil properties and resulting processes, which in turn influence plant development, productivity and competitiveness. Effects of plant-soil feedback influence the plant community succession and ecosystem function.This study choose a succession gradient of abandoned farmland in sub-alpine meadow ecosystem in the east of the Qing-hai Tibetan Plateau. We analyze total species richness, the abundance of each functional groups and their biomass, and soil carbon, nitrogen and other indicators in different successional communities.At the same time, through a potted experiment of wild plant-soil feedback effects, we analyze the change of soil nitrogen forms and the interaction of plants in the succession process and test whether soil N composition control plant community succession of abandoned farmland in alpine meadows. The results showed that:(1)) In the process of abandoned farmland recovery succession, the total species richness in the community increase over time. Following22years, it is close to the level of natural grassland meadow. The species richness and biomass between legume functional groups and total species are closely positive relevant, and ammonia nitrogen content in soil and aboveground plants biomass also is positive relevant. In this N-limited, the composition of nitrogen in the soil may control the succession of the community during succession.(2) In the process of abandoned farmland recovery succession, soil organic carbon, total nitrogen, ammonia nitrogen and nitrate nitrogen content do not increase constantly over time, but increase at first, then reduce, even following37years, it still fail to reach the level of natural meadow. Therefore, abandoned farmland in sub-alpine meadow ecosystem may have a high resilience and a stronger rehabilitating capability and soil restoration have seriously time-lag under natural recovery condition. (3) Whether in abandoned farmland area or in the sub-alpine meadow area, abiotic and biotic soil properties beneath each plant patches are significantly different. Total nitrogen content and organic matter content in abandoned farmland area or in the sub-alpine meadow area have no significant difference, but total nitrogen content in the grasses (Ely nut in abandoned farmland area and Kob hum in the sub-alpine meadow area) higher than the forbs; the content of ammonia nitrogen and phosphorus in the abandoned area is significantly higher than in the sub-alpine meadow area; the content of intrate nitrogen and microbial carbon in Sau acr (abandoned species) and Pol viv (sub-alpine meadow species) is significantly higher than other species.(4) In feedback experiment, we analyze the plant biomass and the difference in soil characteristics. Compared with soil properties before planting, the ammonia nitrogen content has noticeably decrease while nitrate nitrogen content appear different degrees of increase. The content of total phosphorus, total nitrogen and organic matter have no obvious change in the soil which is transplanted five plants. We can draw a conclusion that the composition of nitrogen in the soil may control the succession of the community during secondary succession. Plant-soil show a certain positive feedback in abandoned field. However, both for old-field species and for sub-alpine meadow species, plant-soil feedbacks are negative or positive, depending on species.