Dynamic evolution and landscape ecological risks assessment of Qilu Lake in Yunnan Plateau

Abstract

Objective The research aim is to study the dynamic evolution process of Qilu Lake and its watershed landscape ecological risks under the background of climate change. Method The lake boundary was extracted based on eight time series Landsat images from 1975 to 2015, and three watershed landscape classification data were interpreted. The dynamic evolution of Qilu Lake was studied from the change of lake area, lake shape and the lake centroid. The ecological risk assessment model was established by dividing ecological risk sampling plots, and the landscape ecological risk of Qilu Lake Basin was quantitatively analyzed. Result (1) Over the last 30 years, the landscape structure of Qilu Lake Basin has changed obviously; the area of construction land and beach wetland has increased significantly; the area of farmland, forest land and water area has decreased continuously, and the area of unused land has not changed much; (2) Over the last 40 years, Qilu Lake has been in a continuous shrinking state, and the water area in 2015 is only 56.05% of that in the largest year (1985); Qilu Lake is characterized by continuous and complex changes in shape, the most obvious change is at the entrance of rivers to lake in the west and south part, and the smallest change in the east part; The centroid of Qilu Lake mainly migrates to the northeast, and there is a 1 242 m gap between the centroid in 1975 and that in 2015. The results of ecological risk assessment indicates that the main ecological risk is in lower grade, accounting for 26.75%-35.09% between 1985-2015; The average ecological risk has increased from 0.957 8 to 1.013 9 between 1985-2015, indicating increasing ecological risks. Conclusion The spatial distribution of ecological risk in Qilu Lake Basin has obvious aggregation and spatial heterogeneity. The high ecological risk mainly lies in the Qilu Lake, the low ecological risk mainly in the lake basin, and the other ecological risks mainly in block or band along the lake basin and lake.