Research On Land Use Countermeasures Of Urban Agglomeration In Central Yunnan Based On Carbon Sequestration Effect Evaluation And Prediction Under The Background Of Carbon Neutrality

The carbon storage of ecosystems is an important indicator to measure the carbon fixation capacity of regional ecosystems,while the land use/cover change caused by human activities is the key to affect the carbon fixation effect of terrestrial ecosystems.Actively guiding and adjusting the land use structure and mode will help the carbon cycle process of terrestrial ecosystems.As global warming intensifies,China has put forward the goal of"carbon neutrality"in 2020,making its own contribution to global climate change.In this context,the evaluation and prediction of the carbon sequestration effect of land use is conducive to further analysis of the impact of land use/cover change on carbon sequestration.It also has important reference significance for the realization of regional"carbon neutral"goal and the adjustment of land use policy.This study takes the central Yunnan city cluster as an example.Based on the land use data in 2000,2010 and 2020,this study adopts the analysis methods of land use dynamic attitude and land transfer matrix to grasp the spatio-temporal evolution characteristics of land use in the city cluster in the past 20years as a whole,and uses the In VEST model and the revised carbon density value.This paper further explores the changes of carbon storage in urban agglomerations from the perspective of time and space,and summarizes the impact of land use change on the total carbon storage and carbon sequestration capacity in urban agglomerations.On this basis,PLUS-Markov and In VEST models were used to simulate the total carbon storage and spatial pattern under natural development scenarios,ecological protection scenarios and high-quality development scenarios in2030 and 2060 in central Yunnan city agglomeration.The carbon sequestration effects of land use in the future were further analyzed,and land use optimization suggestions were proposed based on the analysis results.The results are as follows:(1)The land use of urban agglomeration in central Yunnan has changed significantly in the past 20 years,which is specifically shown as follows:from the perspective of time change,the forest land,cultivated land and grassland showed a downward trend from 2000 to 2020,in which the forest land and cultivated land area decreased by 0.27%(297.47km~2)and 0.46%(512.58km~2)respectively.Among the land types with increased area,the increase of construction land is the largest,1.24%(1377.40km~2).On the dynamic degree of land use,the dynamic degree of water area and construction land is the most obvious,1.27%and 10.27%respectively.Among them,from 2010 to 2020,the comprehensive dynamic degree of land use has the most significant upward trend,which is 3.28%,and the change of land use during this period is the most dramatic.From the perspective of spatial change,in the process of land type transfer,the mutual transfer between forest land and grassland is the most significant.During the past 20 years,grassland has transferred 2187.54km~2to forest land,and forest land has transferred 2086.76km~2to grassland.The transferred area of construction land is mainly contributed by cultivated land.The transfer of cultivated land to construction land during 2000-2010 and 2010-2020 was up to 375.32km~2and656.81km~2respectively,showing a multiple growth.It can be seen that with the rapid development of urbanization and the continuous expansion of construction land,the dynamic changes of various categories affected by human activities are becoming increasingly fierce.(2)The carbon storage of the central Yunnan urban agglomeration showed an overall downward trend from 2000 to 2020,with a total decrease of 99.83×10~5t.The carbon storage of the central Yunnan urban agglomeration showed a drastic change from 2010 to 2020,with a decrease value of 73.53×10~5t.The carbon storage in the central Yunnan urban agglomeration presents a trend of"high in the west and low in the east".The high-value areas are mainly concentrated in the northwest and southwest of Chuxiong Prefecture,the middle of Yuxi City,and the northwest and southwest of Kunming City.The low-value areas are mainly concentrated in the south-central and northeastern part of Kunming City,the south and southeast part of Chuxiong Prefecture and Qujing City,and the northeast and southwest part of Yuxi City.In general,the carbon sequestration capacity of central Yunnan urban agglomeration decreased with the decline of carbon storage in the past 20 years.Although the ecosystem carbon sequestration function has a good background and a large number of woodland with high carbon density value,it still has the risk of continuous decline,and the carbon sequestration effect of land use is weakened.(3)In the land use simulation of urban agglomeration in central Yunnan based on PLUS-Markov coupling model,the driving factor contribution analysis shows that GDP is the driving factor with the largest contribution to the expansion of construction land and cultivated land area,and the largest contribution to the expansion of forest land area is DEM.The comparison between the simulation data and the actual data shows that the Kappa coefficient is 0.90,the overall simulation accuracy is 0.93,and the PLUS-Markov coupling model has high reliability.The simulation results of multi scenario land use show that there are significant differences in the spatio-temporal changes of land use under natural development scenarios,ecological protection scenarios and high-quality development scenarios.Compared with 2020,under the natural development scenario,the forest land,cultivated land and grassland of 2030 urban agglomeration will decrease significantly,485.84km~2,414.14km~2and 730.75km~2respectively,while under the high-quality development scenario,they will only decrease 235.20km~2,94.89km~2and 443.94km~2respectively.Under the ecological protection scenario,the area of ecological land has been maintained,but the number of cultivated land has decreased significantly compared with the natural development scenario.In 2030,the area of cultivated land will decline as much as 745.33km~2.The high-quality development scenario better realizes the dynamic balance of land use,and the ecological land and cultivated land are maintained at a high level,so the high-value development scenario is more consistent with the guiding spirit of urban agglomeration planning.(4)Carbon sequestration capacity of central Yunnan urban agglomeration varies under different scenarios.Carbon storage in 2030 under natural development scenario,ecological protection scenario and high-quality development scenario will decrease by114.44×10~5t,47.14×10~5t and 44.51×10~5t,respectively,compared with 2020.Compared with 2020,2060 will decrease by 351.68×10~5t,141.68×10~5t and132.42×10~5t,respectively.The carbon sequestration capacity of high-quality development scenarios is better than other scenarios,and carbon storage in all scenarios presents an overall distribution trend of"high in the west and low in the east".However,as time goes by,the low carbon storage patches have a strong expansion trend.Based on carbon storage,the urban agglomeration was divided into28 districts and counties with low or low carbon sequestration effect,9 districts and counties with medium or high grade,and 12 districts and counties with high or high grade.The low-grade region of carbon sequestration effect under various scenarios at the scale of urban agglomeration is located in the central region of urban agglomeration,the middle-grade region is mainly located in the east and northeast of urban agglomeration,and the high-grade region is mainly located in the west of urban agglomeration.(5)In order to further maintain the stability of carbon sequestration function and give full play to the carbon sequestration effect of land use,based on the analysis results,a series of land use countermeasures and suggestions are proposed for each state,city and urban agglomeration as a whole.Under the scale of administrative division,districts and counties with low and low carbon sequestration effects should strengthen the control of construction land,while districts and counties with medium carbon sequestration effects should maintain the momentum balance between construction land,forest land and cultivated land,while districts and counties with high and high carbon sequestration effects should focus on forest land protection.At the scale of urban agglomeration,the expansion of construction land in the central part of the urban agglomeration is strictly controlled,the forest and grass protection policy is further implemented in the northern part of the urban agglomeration,the conflict between ecological land and construction land should be reasonably regulated in the southern part of the urban agglomeration,the forest land ecological project should be actively implemented in the western part of the urban agglomeration,and the plan of returning farmland to forest and grass should be implemented in the eastern part of the urban agglomeration to ensure the balance of land geology and quantity.Under the natural development scenario,we should focus on curbing the growth rate of construction land.Under the ecological protection scenario,cultivated land protection and ecological land protection are parallel.Under the high-quality development scenario,we should maintain the dynamic balance between ecological land and construction land.