Simulation And Evaluation Of The Impact Of Key Factors Of Global Change On The Net Primary Productivity Of Terrestrial Ecosystem

Climate change,CO₂ and land use/Cover Change(LUCC)are key factors of global terrestrial ecosystem.Studying the influence of these three factors on net primary productivity(NPP)plays an important role in predicting future global NPP and studying terrestrial ecosystem carbon cycle.Climate change,CO₂ concentration change and LUCC have different effects on NPP of terrestrial ecosystem,and there are complex interactions among the three factors.There are few studies on the comprehensive impacts of climate change,CO₂ concentration change and LUCC and the contribution rate of each factor,especially the impact of LUCC on NPP in the future.Therefore,it is of great significance to quantitatively analyze the impact of climate change,CO₂ concentration change and LUCC change on global terrestrial net primary productivity.This study is based on climate data from 2010-2100,using the IBIS(Integrated Biosphere Simulator)model to simulate three typical emission scenarios of global terrestrial ecosystems from 2010-2100(representing concentration paths RCP2.6,RCP4.5 and RCP8.5)the overall change trend of NPP under the influence,and different responses to climate change,CO₂ concentration change and LUCC change.(1)Under the global pattern,the NPP of all latitudes shows an increasing trend,with the most significant change at the end of this century.Its growth trend is mainly caused by the positive effect of CO₂ on NPP,while the effect of climate change is negative.The increase trend of LUCC has only a small positive effect,mainly contributed by the northern mid-latitudes.(2)The climatic factors in the northern high latitudes have had a positive impact on NPP,which reached a maximum of 1.175 Pg C Yr^-1 at the end of the century under the RCP8.5 scenario.Climate factors have a negative impact on NPP in the southern hemisphere,and have the greatest negative impact on NPP in the tropics(-4.842 Pg C Yr^-1).In different regions,CO₂ has a positive impact on NPP,with the strongest impact on tropical regions(8.372 Pg C yr^-1).As the dominant factor,CO₂ has the largest comprehensive impact in Asia under the RCP8.5 scenario(2.868Pg C yr^-1).LUCC has only a small positive impact on NPP,and its overall contribution rate to NPP is only 6.14%.Under the RCP8.5 scenario,LUCC has the greatest positive impact on global NPP from 2010-2020.In the tropics and northern high latitudes,LUCC has the strongest positive and negative effects on NPP,respectively.Under the influence of the LUCC factor,the NPP change in Asia are the most obvious,with an increase of 0.681Pg C yr^-1 from 2010-2020 under the RCP8.5 scenario.(3)There are still some uncertainties in using models to predict the impact of global change factors on NPP.Therefore,analyzing the impact of different factors may provide a basis for predicting the impact of the global NPP and carbon cycle in the future.