| The Loess Plateau is a typical ecologically fragile area and sensitive area in China and even the world.Its ecosystem environmental conditions are fragile and rainfall is scarce,vegetation coverage is low,productivity is low and degradation is serious,so this area is a key area in the process of ecological reconstruction in China and it is also for the implementation of water and soil conservation projects and Green for Grain Project.Under the background of climate change and ecosystem problems caused by global warming,quantifying the carbon sequestration service in the Loess Plateau,exploring its time change,spatial distribution and influencing factors,as well as the relationship between supply and demand services on this basis are important for quantifying the carbon sequestration and oxygen release value of vegetation in the region,evaluating its economic benefits,correctly predicting future climate change and its contribution to ecological services scientific significance.Based on remote sensing data(NDVI data,land use type data,etc.),meteorological data(precipitation,temperature,etc.)and other data(statistical yearbook data of each province,etc.),this paper uses CASA model to estimate the carbon sequestration effect(NPP)of ecological engineering in the Loess Plateau,and based on Sen + MK trend analysis,Hurst index analysis and other methods,explores the carbon sequestration of the Loess Plateau in different time and space scales from 1982 to 2015 Based on the characteristics of time and space change and its influencing factors,this paper analyzes the supply-demand relationship and evolution of carbon sequestration services in 2000-2015.The main results are as follows:(1)The average NPP in the four seasons and growing season of the Loess Plateau has spatial heterogeneity,mainly showing a pattern of high in the southeast and low in the northwest,with the contribution degree from high to low in summer(65.9062 gC/m~2)> growing season(49.4555 gC/m~2)> spring(20.8142 gC/m~2)> autumn(18.1655 gC/m~2)> winter(0.5719 gC/m~2),from the perspective of time change,NPP in the past 34 years showed a curve fluctuation state and an overall growth trend;(2)From 1982s to 2015s,NPP in the Loess Plateau showed an overall increase trend,and the growth trend was larger than its decrease trend,in which the more obvious decrease and increase trend accounted for the largest proportion,respectively 45.2% and 38.1%.The future change trend mainly includes continuous improvement and improvement on the multi-year scale;(3)NPP and precipitation in the Loess Plateau are closely related,but theinfluenceof temperature to NPPisnotverycloseinthisarea.Most areas in the study area have a positive correlation with precipitation,and the closer the area is to the northwest,the higher the correlation is;inthecontrast,the temperature has little correlation with NPP;(4)In this study,the influence of land use change and its transfer on NPP is significant.The increasing range of average NPP of different land use types is forest land > cultivated land > grassland > water area > construction land > unused land.In this study,the influence of land use change and its transfer on NPP is mainly divided into two stages: before 2000s and after 2000s.The results show that before 2000s,the impact of land use change on NPP is mainly reduced,and after 2000s,NPP shows an overall increase trend,and the impact of different land use types and their transfer on NPP is different;(5)from 2000s to 2015s,the supply of NPP as a carbon sequestration service in the Loess Plateau shows an annual growth trend,and the spatial distribution shows that the southeast is stronger and closer to the northwest In the study area,the supply and demand of carbon fixation services are generally tense,and the carbon emissions of heating and electricity are the main demanders of carbon fixation services.The shortage of demand and supply brought by the increase of carbon emissions is the main reason for the tension of supply and demand of local carbon fixation services. |
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