三峡库区土地利用的阶段性响应分析——以库区湖北段为例

Analysis of stage response of land use in Three Gorges Reservoir area: taking Hubei section of the reservoir area as an example

三峡工程历经规划论证、大坝施工、大江截流、下闸蓄水、正式建成和全面运营等6个阶段.以1990年~2015年6期土地利用数据为基础,在ArcGIS平台下提取土地利用双向变化信息,并构建了土地利用程度综合变化指数(Land Use Degree Change, LUDC),对三峡库区湖北段土地利用的阶段性响应进行了分析.结果表明:1)规划论证阶段三峡库区湖北段土地利用(耕地、林地、草地、水域、建设用地)结构是10∶82∶6∶1∶1,正式运营阶段土地利用结构是9∶81∶6∶2∶2,土地覆盖以植被型为主;2)三峡工程不同阶段库区土地利用变化面积、速度/速率及方向差异性显著.蓄水前主要是林地和耕地的相互转换,蓄水后除水面扩展外,宜昌市区建设用地持续大面积增加;3)创建覆盖研究区的1 km×1 km空间网格,以此为单元计算LUDC,土地利用程度综合变化主要发生在500 m以下的河谷地区,且变化与其所处工程建设阶段、国家政策和区域发展规划非常契合,反映了区域生态环境对社会经济发展的响应.在研究区各阶段,影响因素主次有所差异,工程建设和经济发展是土地开发的主要驱动力,建设用地和水域通过占有林地和耕地迅速增加;在移民安置、农业结构调整和生态保护政策影响下,生态环境日益得到改善.研究结果为库区社会经济与生态环境协调发展提供基础数据支撑,也为了解重大水利工程建设对生态系统的影响提供参考.

The Three Gorges Project has gone through six stages:planning demonstration,dam construction,river closure,sluice storage,formal completion and full operation.Based on six land use data from 1990 to 2015,bidirectional land use change information is extracted under the ArcGIS platform,and the Land Use Degree Comprehensive Change Index(LUDC)is constructed to analyze the phased response of land use in Hubei section of the Three Gorges reservoir area.The results show that the land use(cultivated land,forest land,grassland,water area and construction land)structure in the Hubei section of the Three Gorges Reservoir area is 10∶82∶6∶1∶1,and that in the formal operation stage is 9∶81∶6∶2∶2.The land cover in the study area is dominated by vegetation type.The land use change area,speed/rate and direction of the reservoir area at different stages of the Three Gorges Project are significantly different.Before the impoundment,the main performance is the mutual conversion of forest land and cultivated land.After the water storage increases,the construction land in Yichang City continues to increase in large areas.We also created a spatial grid at a resolution of 1 km×1 km covering study area and calculated the LUDC index.The comprehensive change of land use degree mainly occurs in the valley area below 500 m,and the change is very compatible with the national policy and regional development plan at the stage.It reflects the response of regional ecological environment changes to social and economic development.In all stages of the study area,the priority of influencing factors is different.Engineering construction and economic development are the main driving forces for land development.Construction land and water areas increase rapidly through the occupation of forest land and cultivated land.The ecological environment is getting better and better due to resettlement and agricultural structure adjustment and ecological protection policies.The research results provide basic data support for the coordinated development of the social economy and ecological environment in the reservoir area,and references for understanding the impact of major water conservancy projects on the ecosystem.