Carbon Storage And Its Influencing Factors Of The Grassland In Three River Sources Region

Carbon pool of the grassland ecosystem plays an important role in global climate change as well as material and energy cycle.Accurate understanding the above-and below-ground biomass,soil carbon stocks and its influencing factors will be benefit to comprehending the feedbacks between terrestrial ecosystem and climate change.Our study was conducted in the grassland ecosystem of Three River Sources Region.We investigated plant,soil and the whole ecosystem carbon storages and distribution under different grassland types according to vegetation types and remote sensing data,and analysed the relationships with precipitation,temperature and elevation.We also explored the effects of exclosure,rodent control and the treatment of "black soil land"on carbon density and carbon sequestration rate under different grassland types.The main findings are as follows:(1)The ecosystem carbon density in different types of grassland ecosystem was alpine meadow(16.91 kg C m-2)>alpine steppe meadow(12.65 kg C m-2)>temperate steppe(8.97 kg C m-2)>temperate desert steppe(6.62 kg C m-2)>Alpine steppe(6.38 kg C m-2).Soil carbon pool that is the main component of the whole ecosystem carbon pool,accounted for 87.5%,79.9%,93.0%,89.0%and 78.7%,respectively.(2)The above-and below-ground biomass and soil organic carbon had positive relationship with precipitation(p<0.01).Except there was no relationship between aboveground biomass and annual mean temperature,the belowground biomass and soil organic carbon were correlated with annual mean temperature and average temperature in growing seasaon,and showed a parabolic trend.Elevation did not influence aboveground biomass and soil organic carbon,but exerted a significant impact on the belowground biomass,and a quadric relationship was observed.Moreover,soil organic carbon was positively correlated with above-and below-ground biomass as well as total biomss.(3)Plant biomass carbon,soil carbon and the whole ecosystem carbon destiny was estimated at 490.65Tg,2487.47 Tg and 3069.98Tg,respectively,according to MODIS-NDVI method.Plant biomass carbon,soil carbon and the whole ecosystem carbon destiny had a similar distribution trend,and decreased from southeast to northwest.Grassland ecosystem carbon density was lowest in Zhiduo and Tanggula,which is located in alpine steppe of upper Yangtze river and alpine desert steppe of Kekexili area,had the lowest ecosystem carbon density.The main vegetation types were alpine shrub and alpine meadow in Banma and Jiuzhi of yellow river source area,in which there had the highest ecosystem carbon density.(4)After the degradation grasslands were fenced for 5 years in Three River Sources Region,ecosystem carbon pool significantly increased.Carbon sequestration rate in the alpine meadow and alpine grassland was 213a 8 g C·m-2 yr-1 and 92·1 g C·m-2 yr-I,respectively.Rodent control could promote carbon fixation in alpine meadow grasslands.The carbon sequestration rate was 68.4 g C·m-2 yr-1.While rodent control had no significant effects on carbon sequestration in alpine steppe grasslands.The Treatment of“black soil land”could improve the properties of vegetation and soil,thus increased carbon sequestration in alpine meadow ecosystem.The carbon sequestration rate was165.8 g C·m-2 yr-1.It is one of the most effective ways for restorating the severely degraded grassland...