Response Of Ecosystem Service Value To Land Use Change In Nanning City

With the rapid development of urbanization,extensive land use patterns lead to ecological environment destruction,and have a profound impact on the spatial pattern of ecosystem service value(ESV).Nanning not only is the capital of Guangxi Zhuang Autonomous Region but also the political,economic and cultural center,as well as the permanent venue of China-Asean Expo.Besides,Nanning is also a comprehensive transportation hub that connecting southwest China to the sea.Therefore,in the rapid development of social economy,how to ease the contradiction between human and land,maintaining the healthy and stable ecological environment is of great significance to promote the sustainable development level of Nanning city.Based on the remote sensing image data of Nanning in 2005,2010,2015 and 2020,six land use types(arable land,forest land,grassland,water area,construction land and unused land)were obtained.Based on the spatial analysis function of Arcgis software,the land use type change,land use speed change,land use degree change and transfer matrix characteristics of Nanning city from 2005 to 2020 were discussed.Based on the land use data from 2005 to 2020,the ESV equivalent of the study area,farmland food yield,social development coefficient and resource scarcity coefficient were comprehensively revised to establish the ecosystem services assessment model of Nanning.Then,the spatial and temporal characteristics of ESV in Nanning from 2005 to 2020 were analyzed by using grid cells,and the spatial autocorrelation dynamic changes were explored.The results show that:(1)From the perspective of the overall land use structure and change in the four periods from 2005 to 2020,the main types of land use in Nanning were woodland(11647.69 km~2-11690.59 km~2)and arable land(7395.05km~2-7573.85km~2).Grassland(1302.51km~2-1339.73km~2),building land(871.96 km~2-1162.61 km~2),water area(615.99 km~2-649.47 km~2)and unused land(2.30 km~2-4.05 km~2)were the second.(2)From 2005 to 2020,all types of land use in Nanning changed to different degrees,except for the increase of construction land and unused land area,the other types of land area decreased.The dynamic attitude of unused land was the largest(5.10%),followed by construction land(2.22%),while the dynamic attitude of water area,grassland,arable land and forest land was-0.34%,-0.19%,-0.16%and-0.02%,respectively.(3)ESV of Nanning decreases from 810.40×10~8yuan in 2005 to795.14×10~8yuan in 2020(a total decrease of 15.26×10~8yuan),which was mainly due to the influence of the national"Belt and Road Initiative"gateway city construction policy,which made Nanning develop rapidly in recent years and people develop natural resources frequently.The area of land used for construction continued to increase.From the perspective of ecosystem service value contribution of each land use type,forest land had the highest ecosystem service value,accounting for 56.03%of the total service value,because forest land area accounted for the largest proportion.Arable land,water,grassland and unused land were next.(4)Based on grid units,the ecosystem service value hierarchy of Nanning city could be divided into low,relatively low,medium,relatively high and high value regions.From 2005 to 2020,the ecosystem service value of Nanning was mainly in low value area,accounting for more than50%of the total area,mainly distributed in Jiangnan District,Liangqing District,Yongning District and other urban core areas.The area of the middle and relatively high value was mainly distributed in Longan County and Liangqing District.The area of the high value area accounted for about 13%of the total area,which was clustered in the northwest to southeast clumps and distributed in Shanglin County,Binyang County,Mashan County and other suburban areas.(5)From 2005 to 2020,the value of ecosystem services in Nanning had a significant positive spatial correlation,and the degree of agglomeration was increasing.The dense clusters were mainly distributed in Binyang County and Wuming district in the east and north of Nanning city,because these areas were rich in water and forest resources and had high ecosystem service value.Non-dense agglomerations were mainly distributed in Jiangnan district and Liangqing District in the southwest and southeast of Nanning city and other rapidly developing urban areas,because the construction land and unused land in these areas were widely distributed and the ecosystem service value was low.During the past 15years,the changes of dense and non-dense agglomerations were obvious,while the changes of other spatial autocorrelation agglomerations were small.