Effects Of Carbon And Nitrogen Addition, Fencing And Mowing On Soil And Vegetation Of Alpine Meadow In Northern Tibet

Increased atmospheric nitrogen deposition since last many years has resulted disorders in the global nitrogen cycle. Disturbances of the nitrogen cycle may cause changes in the carbon cycle. However, effects of Nitrogen on the alpine meadow plant community structure and biomass is still controversial, the impact of exogenous carbon on the Qinghai-Tibet alpine meadow plant community structure and biomass are uncommon. This study was carried out in Tibet Nagqu fenced alpine meadows. On the basis of the previous three years to continue more carbon gradient(sucrose), nitrogen(urea) was added and fencing, mowing, carbon, nitrogen addition interactivity to test, explore carbon and nitrogen addition fence and mowing alpine plant species diversity characteristics of biomass and the effect of soil physical and chemical properties. This study was carried out in the following two parts: 1 effects of carbon and nitrogen addition on Northern Alpine meadow soils and vegetation. 2 Interaction of carbon, nitrogen addition, enclosures, mowing on the Northern Alpine meadow soils and vegetation.Following conclusions have been drawn from this research:1 carbon, nitrogen addition and fencing of alpine meadow increased aboveground biomass during five years significantly while no significant effect was found on aboveground biomass of natural degraded grasslands. Fencing and cutting significantly increased aboveground plant biomass.2 carbon, nitrogen addition did not show significant effects on the alpine meadow plant community diversity. Species diversity of grassland fencing during five years was significantly higher than the natural degradation of community species diversity.3 addition of nitrogen significantly reduced alpine meadow soil p H, but added N cause a reduction in the second year of the soil p H can get a better recovery. Carbon addition has significant effects on alpine meadow soil p H, but the added carbon in Alpine soil p H varied between the seasons.4 carbon and nitrogen addition showed a significant impact on the alpine meadow soil organic carbon and only nitrogen significantly lowered alpine meadow soil organic carbon content. But in the second year you can get a better recovery. Fenced grasslands soil organic carbon content was significantly higher than degraded grassland soil organic carbon content during five years. Carbon and nitrogen addition on the one hand can increase the total nitrogen content of the soil surface, but in the second year can get a better recovery, fenced grassland soil total nitrogen content was significantly higher than the five-year total nitrogen content of the soil of degraded grassland. Carbon and nitrogen addition had no significant effect on the total phosphorus content of the soil. Fenced grassland soil effect on total phosphorus content during five years was significantly higher than that of degraded grassland soil total phosphorus content.5 carbon and nitrogen addition on the one hand can increase the total nitrogen content of the soil surface, but also so that there is total soil nitrogen to the surface tend to move together.