长江三峡库区土地利用/覆盖的长期变化

了解土地利用/覆盖的时空变化有助于揭示气候变化和人类活动对生态系统的影响,是开展生态系统管理的重要前提.长江三峡库区是我国重要的生态脆弱区,环境变化影响的复杂性显著,但目前对此仍缺乏系统了解.本文通过解译Landsat时序遥感影像,获取三峡库区土地利用/覆盖数据,研究土地利用/覆盖构成结构及其分布的长期时空变化特征,以揭示三峡库区土地利用/覆盖的演变规律,为深入了解生态脆弱区生态系统变化复杂性和区域生态系统管理提供科学依据.结果表明: 1990—2015年间,三峡库区土地利用/覆盖结构的空间异质性和变化显著,农田面积比例由66.2%降至40.4%,林地面积比例由31.3%增至53.5%,库区由农业景观转变为以森林、灌木林等为主的林地景观,建设用地和水体逐渐增加;林地逐渐向库区中部扩张,建设用地点状扩张;海拔500～1000 m和坡度15°～25°区域林地面积比例增长最明显,针叶林、针阔混交林和灌木林等植被类型增长最快.研究期间,三峡水库建设和各类生态恢复工程的实施促使区域土地利用/覆盖结构呈阶段性变化,总体表现为生态恢复趋势.积极的生态恢复措施有助于消减工程建设对区域生态环境的负面影响.

Long-term changes of land use/cover in the Three Gorges Reservoir Area of the Yangtze River,China.

Understanding the temporal and spatial dynamics of land use/cover (LUC) can contri-bute to reveal the impacts of climate change and human activities on ecosystems and thus be an important prerequisite for ecosystem management. As an ecologically vulnerable area in China, the Three Gorges Reservoir Area (TGRA) of the Yangtze River presented significant complexity in the response to environmental changes. However, there is a general lack of understanding in the underlying mechanism. In this study, we interpreted the time series remote sensing images derived from the Landsat sensors to map the LUC of the TGRA, and aimed to analyze the long-term changes in the distribution and structure of LUC and elucidate the evolution process of LUC, which could provide a scientific basis to understand the complexity of ecosystem changes and regional ecosystem management in ecologically fragile regions. The results showed that the TGRA presented the significant changes in spatial heterogeneity of LUC structure from 1990 to 2015. Meanwhile, the landscape changed from farmland to woodland (forest and shrubland). Farmland decreased from 66.2% to 40.4%, but woodland increased from 31.3% to 53.5%, buildings and water area increased gradually. Forest gradually spread to the middle of the TGRA, while the buildings presented a scattered expansion. In the altitude zone of 500-1000 m and slope zone of 15°-25°, woodland increased noticeably, and the coniferous forest, mixed forest and shrubland had a higher growth rate. In the study period, due to the urban construction and the various ecological restoration projects in the TGRA, the LUC structure varied with the dam’s impoundment and was characterized by the ecosystem restoration. Ecological restoration projects were helpful to reduce the negative impacts of urban construction and economic development on the environment.