| The various environmental problems associated with rapid urban development have affected the ecological processes on the land surface,leading to a rise in carbon dioxide concentration and global warming,which seriously affect and threaten the sustainable development of human society.Plants have the capacity to be carbon sinks and are an important factor in achieving carbon balance.Therefore,green ecological spaces made up of plants have become a key target for conservation and development as natural carbon sinks in cities.The relationship between various influencing factors and the carbon sink of green ecological space can be studied in a long time series,which can provide a scientific basis for guiding the growth of the carbon sink of green ecological space.In this paper,the spatial and temporal changes of carbon sinks in the green ecological space of Xi’an from 1995 to 2019 are studied,and how each factor affects the changes of carbon sinks in the green ecological space is analysed.The findings of the study can reveal the patterns of the various influencing factors and the changes of carbon sinks in green ecological space,and provide relevant suggestions for the growth of carbon sinks in the green ecological space of Xi’an.The research of this paper includes the following three parts.Firstly,studies on the influencing factors of carbon sinks were integrated,mainly classifying and summarising external environmental factors,and using them as the basis for selecting the influencing factors applicable to the analysis of carbon sinks in the green ecological space of Xi’an.Secondly,the evolution of the green ecological space in Xi’an over a 25-year period is analysed in terms of land use and vegetation cover changes.The spatial and temporal distribution and trends of carbon sinks in Xi’an over a 25-year period are estimated using the CASA model,and the relationships between the changes in carbon sinks and land use and vegetation cover changes are obtained.Finally,the relationships between temperature,precipitation,solar radiation,human activity intensity and landscape pattern and green ecological carbon sinks are analysed on a meta-by-meta basis,and on this basis,the comprehensive influencing factors leading to different trends of green ecological carbon sinks in Xi’an are analysed.The study also proposes recommendations for the growth of green ecosystem carbon sinks in Xi’an.From the above study,the following conclusions were drawn.（1）The area of green ecological space in the Xi’an metropolitan area has been on an increasing trend between 1995 and 2019,with a total increase of 859.98 km2during the study period,while vegetation cover shows a significant increase;carbon sinks in some areas of green ecological space have increased significantly due to the increase in vegetation cover and land use transformation.（2）The average multi-year carbon sink in the green ecological space of Xi’an decreases from south to north,with the average value of carbon sink in the Qinling region being 120 g/C m-2,while the average value in the region north of the Qinling is only 46 g/C m-2,with significant differences.（3）Among the climatic factors,the degree of correlation between forest carbon sinks and various climatic factors varies significantly among regions;temperature and precipitation are the main factors affecting grassland carbon sinks,and both are positively correlated.With regard to the intensity of human activities,in the regions north of the Qinling Mountains,anthropogenic activities such as increasing the amount and area of green areas and returning farmland to forests can effectively promote the growth of carbon sinks in green ecological space,while some woodlands in the Qinling Mountains are sensitive to human activities.In terms of landscape pattern,a more fragmented and clustered layout is more conducive to the enhancement of carbon sinks in the green ecological space north of the Qinling Mountains.（4）In the Qinling region,changes in green eco-spatial carbon sinks are mainly influenced by single or multiple climatic factors,and influenced by human activities only near the 25-degree slope line of the Qinling Mountains;while for the region north of the Qinling Mountains,human activities are the main factor causing changes in green eco-spatial carbon sinks,and show a positive influence,mainly in the northern foothills of the Qinling Mountains and the strip green areas on both sides of various rivers. |
