近40年来洞庭湖流域土地利用及生态风险时空演变分析

Spatial⁃temporal evolution of land use and ecological risk in Dongting Lake Basin during 1980-2018

以洞庭湖流域为研究对象,利用1980年、1990年、2000年、2010年和2018年5个时期的土地利用数据,在定量分析近40年流域土地利用动态特征的基础上,从景观生态学视角构建生态风险评价模型,对1980—2018年洞庭湖流域生态风险进行评价,并进一步揭示其时空格局演变特征。结果表明:(1)1980年以来,洞庭湖流域土地利用类型以林地和耕地为主。洞庭湖流域土地利用格局发生较大变化,其显著特征为建设用地不断扩张、林地基本稳定、耕地日益萎缩和水域呈扩大趋势。(2)近40年来,洞庭湖流域生态环境较为良好,以较低和中等生态风险区为主导类型。在1980—1990年、1990—2010年和2010—2018年3个时段内,生态风险呈现增长、缓和、加剧的变化过程,高风险区以洞庭湖湖盆向环洞庭湖平原扩张,洞庭湖区、湘江流域和资水流域生态风险等级明显高于其他地区,而沅水流域、澧水流域和湘江流域的东南部生态风险相对较小。

Land use change is the most direct manifestation of the interaction between human activities and the natural environment,which can significantly change the pattern of the ecosystem,and then affect the process and function,thus having a far⁃reaching impact on the regional ecological environment.Ecological risk plays an important role in ecological environment quality assessment and ecological environment management,which can better reflect the impact of land use change on ecological process and function.The Dongting Lake Basin,which flows through Hunan,Hubei,Jiangxi,Guangdong,Guangxi,Guizhou and Chongqing,is situated in the middle and lower reaches of the Yangtze River basin in the central south of China.It is famous for its agricultural products.In this article,land use data in 1980,1990,2000,2010,and 2018,were used.Land cover types were interpreted,and the dynamic characteristics of land use were quantitatively analyzed.In addition,the ecological risk assessment model was constructed to evaluate ecological risk from the perspective of landscape ecology,thereby revealing the characteristics of spatial⁃temporal evolution.The results showed that(1)since 1980,the land use types of Dongting Lake Basin were mainly woodland and cropland.The land use pattern has taken great changes,which is characterized by the continuous expansion of built⁃up land,the basic stability of woodland,the shrinking of cropland and the expansion of water area.(2)the ecological environment of Dongting Lake Basin showed a relatively good state,with lower and medium ecological risk areas as the dominant type during 1980-2018.In the three periods of 1980-1990,1990-2010 and 2010-2018,ecological risk has been increasing,mitigating and aggravating.High risk areas were mainly distributed in Dongting Lake and Dongting Lake Plain.Moreover,the ecological risk of Dongting Lake region,Xiangjiang River Basin and Zishui basin were significantly higher than that of other areas,while it was a lesser risk extent in Yuanshui basin,Lishui basin and the east and south of Xiangjiang River Basin.