| Land use change is a key factor affecting carbon emissions.Quantitative analysis of the impact of land use change on carbon stocks is helpful to construct land use structure with low carbon emissions and formulate climate change response strategies.Chang-Zhu-Tan metropolitan circle(abbreviated as CZTM)is an important part of the Yangtze River Economic Belt and the rise strategy in the middle part of our country.Green and low-carbon development has become a new trend in the construction of metropolitan circle in the future.Based on the land use data from 2000 to 2020,this paper analyzed the spatial and temporal changes of land use and its ecological effects,taking CZTM as the research object.Combined with scenario analysis method,PLUS model and In VEST model,land use change under natural increase scenario(NIS),economic development scenario(EDS)and ecological protection scenario(EPS)during 2020-2050 was simulated to reveal the main driving factors of land use change and explore the impact of land use change on carbon storage.The main research conclusions are as follows:(1)From 2000 to 2020,the area of cultivated land,forest land,grassland and wetland decreased,while the area of water and construction land increased.The dynamic attitude of comprehensive land use was 5.16.Forest land was the main land use type in the study area,and also the land type with the largest area reduction.Construction land was the land category with the fastest expansion rate,and its main expansion stage was from 2010 to 2020,mainly coming from forest land and cultivated land concentrated in Ningxiang City,Changsha County and the central urban area.The average RSEI index of forest land was as high as 0.74,being of great significance for maintaining the ecological environment quality in the study area.(2)The overall accuracy of land use simulation was 84.68%,Kappa coefficient was about 0.739,and Fom value was about 0.238.DEM,NDVI and distance from water had great influence on the expansion of cultivated land,forest land and water.The expansion probability of construction land was greater in the area with high night light value,which had a limiting effect on the development of cultivated land and forest land.Soil type played a decisive role in wetland expansion,and grassland expansion was mainly affected by DEM,NDVI,GDP,slope and average annual temperature.Compared with NIS,construction land would expand more rapidly and ecological land would decrease more rapidly under EDS during 2020-2050,while construction land would slow down and ecological land would be effectively protected under EPS.(3)The carbon storage of the CZTM in 2000,2010 and 2020 were 231.83 Tg,231.48 Tg and 221.07 Tg,respectively,showing a high spatial distribution in the east,medium in the west and low in the middle.Liuyang City was the largest carbon storage area and the most reduced area with a reduction of 1.54 Tg.Under these three scenarios from 2020 to 2050,the carbon storage reduction in the study area was EDS(29.45Tg)>NIS(25.27Tg)>EPS(19.04Tg).Forest land was the main carbon pool,and its area decline was the main reason for the loss of carbon storage in the study area.The conversion of forestland and cultivated land to construction land would lead to a sharp decline in carbon storage,while the conversion of cultivated land,grassland and construction land to woodland and wetland was conducive to the formation of carbon storage.Compared with NIS and EDS,EPS development model could promote the development of forest land,grassland,wetland,thus effectively slow down the carbon loss rate in each district and county.In the future,the CZTM should slow down carbon emissions and enhance carbon storage capacity through strict control of construction land and active ecological protection and ecological restoration measures based on the EPS development model.The results can provide a scientific basis for the optimization of land use pattern in the CZTM under the " carbon peaking and carbon neutrality " target. |
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