Spatial and temporal dynamics of large natural lake areas and shoreline morphology in the Yellow River Basin.

Given their important roles in the regulation and storage functions for river flow and in the regional ecological environment and ecosystem services, natural lakes are essential for the ecological protection and high-quality development of the Yellow River Basin. We used the Landsat TM/OLI remote sensing data to analyze the area changes of Dongping Lake, Gyaring Lake, and Ngoring Lake, three representative large natural lakes in the Yellow River Basin from 1990 to 2020. We used the landscape ecology approach to study the morphological characteristics of lake shoreline and shoreland changes and the relationship between the landscape indices. The results showed that the main areas of Gyaring Lake and Ngoring Lake were mainly in the trend of expansion, while the main area of Dongping Lake significantly reduced during 1990-2000 and 2010-2020. The changes in the area of lake all occurred mainly near the lake inlet of the river. The shoreline morphology of Dongping Lake was more complex, with the fragmentation and aggregation of shoreland landscape significantly changed. The circularity ratio of Gyaring Lake gradually decreased with the expansion of the lake area, and the number of patches in its shoreland changed significantly. The fractal dimension index-mean of the shoreland of Ngoring Lake was relatively high, the complexity of its shoreline landscape was stronger, and the number of patches had increased significantly from 2000 to 2010. Meanwhile, there was a significant correlation between certain lake shoreline (shoreland) landscape indices. The changes in circularity ratio and shoreline development coefficient caused changes in the patch density of shoreland.

[Evaluation of ecological environment and urban development quality in Xi'an City, China]. / 西安市生态环境及城市发展质量评估.

Sound ecological environment is an important foundation for promoting high-quality urban development, as it determines the level and quality of urban construction and human settlements. Taking Xi'an as the study area, we used remote sensing ecological index (RSEI) to evaluate the urban ecological environment. The evaluation index system of high-quality urban development was constructed and the entire-array-polygon was used to evaluate the urban development quality. The coupling coordination degree model was used to analyze the temporal variations of the coupling coordination degree of those two factors. The results showed that the urban ecological condition of Xi'an showed a pattern of high in the south and low in the north, and that the level of RSEI had an upward trend in 2010-2020. The RESI of the six inner districts of Xi'an decreased, but the RESI of the surrounding districts of Xi'an was stable or improved. The urban development quality of Xi'an was improved in 2010-2020, though the quality level was still at the low level. The improvement of the three major subsystems of urban development was uneven, and the increase range of three subsystems from largest to smallest was ranked as ecological subsystem > economic subsystem > social subsystem. The coupling coordination of the two kinds of index increased in 2010-2020, and the coordination level had been prompted from barely coordinated to primary.

[Spatial and temporal variations of ecosystem service synergy and trade-off in Qinling Mountains, China]. / 秦岭生态系统服务协同与权衡的时空异质性.

The Qinling Mountains are an important ecological function area in China. Exploring the trade-offs and synergies of ecosystem services is important for ecological protection and sustainable development in the Qinling Mountains. In this study, we analyzed the spatio-temporal variations of land uses in the Qinling Mountains in 2000, 2010 and 2020 based on remote sensing, meteorological, and soil texture data. The amounts of carbon sequestration, water yield, habitat quality, and soil conservation were calculated with CASA, InVEST and RUSLE models. The relationships between its spatially heterogeneous characteristics and various ecosystem services were analyzed. The results showed that, from 2000 to 2020, the area of arable land and grassland in the study area continued to decrease, the area of forest and building land increased, and the change of water body and unused land was not noticeable. Carbon sequestration was high in the east and low in the west, with an increasing trend. Water production continued to decrease, showing a tendency of higher on the south slope and lower on the north slope. Habitat quality increased steadily, while soil conservation increased and then decreased. Ecosystem services varied across land classes and across ecosystems in the same land class. In general, there was a synergistic relationship between carbon sequestration and soil conservation, habitat quality and soil conservation, carbon sequestration, and habitat quality. There was trade-off between carbon sequestration and water production, soil conservation and water production, habitat quality, and water production. There were significant differences in the relationship between service volumes under different conditions. The results could reduce the risk of trade-offs and maximize overall benefits, and provide a reference for promoting ecologically high-quality development and achieving a win-win situation for natural resource management and human well-being.