NPP Estimation And Scenario Simulation Of Grassland In Qinghai-tibet Plateau Based On Biome-BGC Model

The Qinghai-Tibet Plateau is vast and rich in resources.The grassland area accounts for about one-third of the country's total grassland area,which is significantly affected by climate change.In order to study the response of the Net Primary Productivity?NPP?of the Qinghai-Tibet Plateau to climate change,this study has mainly completed the following aspects based on the Biology Geochemical model?Biome-BGC model?:estimation of NPP changes in grassland of 14 meteorological stations has been completed on the Qinghai-Tibet Plateau from 1961 to 2017;responsive research of exploring the response of NPP to climate factor changes has been discussed;based on climate prediction data from different scenarios?RCP8.5,RCP6,RCP4.5,RCP2.6?issued by the Intergovernmental Panel on Climate Change?IPCC?,prediction of NPP in 2050²099 has been achieved.The main conclusions are as follows:?1?The NPP of the Qinghai-Tibet Plateau showed an increased trend from 1961to 2017,with the highest NPP at the Dari site,which was 256.05 gC·m^-2·a^-1,the lowest NPP at the Golmud site,and the largest annual growth rate of the NPP at the Dulan site?1.62%/a?,and the growth rate of Chai Dan and Gangcha is the lowest?0.01%/a and 0.08%/a?.The change trend of NPP is closely related to the change of climatic factors,which shows that the NPP growth rate of most sites increases with the increase of climatic factor growth rate,and conversely reduce.?2?NPP accumulation in meadow grassland of Qinghai-Tibet Plateau is more significant than that of typical alpine grassland and typical alpine desert grassland.The typical alpine desert grassland has the lowest NPP accumulation due to rare precipitation.The NPP distribution of grassland shows two laws of regional differences and vertical zonal.The NPP of sites at the south of the 34.217°N and the low-altitude are higher than sites at the north of the 34.217°N and high-altitude.?3?Under the condition of constant precipitation,the optimal heating threshold of the Tuotuohe site is 0.5°C,and the heating threshold of the Wudaoliang site is 2°C or higher;under the condition of constant temperature,the optimum threshold of water increase in he Geermu,Litang and Deqin sitesis is 10%²0%,and the water increase at Ganzi,Gangcha and Wudaoliang sites should be less than 10%.The optimum water increase threshold for sites such as Chaidan,Dari,Dulan and Lhasa exceeds the 20%set in this study.?4?Under the same precipitation conditions,the warming caused significant changes in NPP at the site in the central Tibetan Plateau,while in other sites,the change of NPP is not significant.?5?In the Qumalai,Wudaoliang,Shigatse,Nagqu,Lhasa,Ganzi,Dulan,Deqin and Chaidan sites,the RCP2.6 scenario is more suitable for grassland productivity than other scenarios.In the studies of Dari and Gangcha,the climate change simulated in the RCP4.5 scenario is suitable for the accumulation of grassland productivity;the RCP8.5 scenario in the Litang site is more suitable for the accumulation of grassland productivity than other scenarios.The climate set by RCP8.5 scenario is the most suitable for grassland growth at Litang Station.