| Clarifying the carbon cycle system is an important basis for China to achieve its strategic goals of“emission peak”and“carbon neutrality”.The spatiotemporal patterns of vegetation carbon sinks in the Yellow River Basin,an important ecological security barrier in China,are not clear from different perspectives;The driving mechanisms of vegetation carbon sinks and the contribution of climate drivers and human activities to vegetation carbon sinks remain unclear.In addition,the transfer characteristics and driving mechanisms of land-use change in the Yellow River Basin,and the impact on carbon storage,are not yet clear.In this study,Gross Primary Production(GPP)data from Solar-Induced Chlorophyll Fluorescence(SIF)was used as an indicator of vegetation carbon sink.Based on trend analysis,Geodetector and the Terrestrial Ecosystem Model(TEM),the spatiotemporal patterns of GPP in the Yellow River Basin from 2001 to 2020 were investigated from the perspective of interannual,seasonal and vegetation types,the driving mechanisms of GPP under the interaction of multiple factors were analyzed,and the contributions of climate drivers and human activities to GPP were determined.In addition,based on the land use data of the Yellow River Basin in 2000,2010 and 2020,the land use shift was analyzed,and the Patch-Generating Land Use Simulation Model(PLUS)was used to explore the driving mechanisms of land use change and project the land use situation in2030.The revised carbon pools were introduced into the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model to estimate carbon storage in the Yellow River Basin for four periods from 2000-2030.The main findings of this study are as follows:(1)The SIF-GPP data from solar-induced chlorophyll fluorescence inversions fit well with the EC-GPP data measured at the Eddy Covariance Flux Tower(EC),which can effectively reveal the characteristics of GPP changes in the Yellow River Basin.During the period 2001-2020,the interannual GPP in the Yellow River Basin shows an overall upward trend,with areas of rapid GPP decline spatially scattered,mainly in large and medium-sized cities where humans are concentrated,and in small localized areas strongly affected by human activities.The improvement of vegetation in the Yellow River Basin accelerated the growth of GPP.Simultaneous rain and heat and higher evapotranspiration contributed to GPP accumulation,while extremely low values of temperature inhibited GPP accumulation.(2)GPP in the Yellow River Basin mainly shows a spatial aggregation of high values,with different degrees of influence of each factor on GPP,mainly as follows:Leaf Area Index(LAI)(0.875)>Precipitation(Pre)(0.663)>Evapotranspiration(ET)(0.433)>Temperature(Temp)(0.341).However,the explanatory power for the spatial heterogeneity of GPP after the multi-factor interaction all showed a non-linear enhancement,where ET and Temp were both exponentially non-linearly positively correlated with GPP,while LAI and Pre were linearly positively correlated with GPP.GPP in the Yellow River Basin is influenced by both climate-driven and human activities,but there are regional differences,with the positive climate-driven effect on GPP in the Yellow River Basin concentrated on the Tibetan Plateau and Qilian Mountains in the western part of the basin,as well as the heavily vegetated forests in the southeast,while the positive human activity effect on GPP is mainly concentrated in the farming areas in the southeast,showing significant seasonal variations.(3)In the Yellow River Basin,between 2000 and 2020,the area of forest,grassland,water and construction land increased,while the area of cropland and unused land decreases,and the carbon storage in the whole basin increases by 33.51×10~6t,showing a spatial pattern of"high in the south-east,low in the north,medium in the center and mixed high and low in the west".Reveals that the continued urbanization of the Yellow River Basin has been accompanied by the effective implementation of environmental protection policies.Based on the PLUS model it is predicted that some of the forest around existing cities in the Yellow River Basin will be converted to building land in the future,and some of the unused land in the northern part of the basin is expected to be developed into building land and forest.Based on the InVEST model,the whole basin carbon storage will continue to increase by 14.00×10~6 t in 2030.The research provides theoretical and technical support for ecological protection and high-quality development in the Yellow River Basin. |
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