Evolution of Ecological Patterns of Poyang Lake Wetland Landscape over the Last One Hundred Years Based on Historical Topographic Maps and Landsat Images

Abstract

Ecological pattern evolution of Poyang Lake wetland, the largest freshwater lake in China, is critical for regional ecological protection and sustainable development of migratory bird habitats; however, this information is still not fully explored. In this study, we quantitatively reconstructed the spatial distribution and landscape ecological pattern of Poyang Lake wetlands in three periods in the past 100 years based on the military topographic map in the 1930s and the Landsat satellite remote sensing image data in 1979 and 2021. Further, use the Fragstats software to analyze the ecological pattern index of wetland reconstruction results. The results show that the wetland area in the Poyang Lake region has experienced a continuous reduction process over the past 100 years, and it decreased from 3857 km2 in the 1930s to 3673 km2 in the 1970s, and then to 3624 km2 in the 2020s. The current wetland area has decreased by about 6.04% compared with the 1930s. The general trend of changes in the spatial pattern of Poyang Lake wetlands is that the surface water decreases and the open land increases. Nevertheless, the trend has certain spatial differences as a large area of wetlands disappeared in the southwest and west of Poyang Lake and the areas with enlarged wetland density values mainly appeared in the northeastern and northern parts of the study area. The NP (number of patches) in the wetlands of Poyang Lake over the past 100 years showed a downward trend during the 1930s–1970s, and an increasing trend during the 1970s–2010s. Due to the increases of constructed wetlands, the number and density of patches also increased, and PD (patch density) reached a maximum value of 0.142 in 2020s. The LPI (largest patch index) has shown a gradual downward trend in the past 100 years. Compared with the 1930s, the wetlands in 2020s dropped by about 26.64%, and the wetlands further showed a trend of fragmentation. The AI index, which indicates the concentration of wetland patches, reached the maximum value in 2020s, but the LSI (landscape shape index) showed a downward trend in general, indicating that the shape of wetland patches has been simplified over the past 100 years. The research results can provide basic data and decision-making basis for Poyang Lake wetland protection, construction of migratory bird reserve and regional sustainable development.

Water Occurrence in the Two Largest Lakes in China Based on Long-Term Landsat Images: Spatiotemporal Changes, Ecological Impacts, and Influencing Factors

“…NPP is an important ecosystem service provided by Poyang Lake. Ye et al [22] observed that annual NPP shows a significant negative correlation with water inundation duration in Poyang Lake, and the correlation intensity is far greater than that of the other three influencing factors (air temperature, solar radiation, and precipitation) that control This study showed that there were many similarities in the spatial and temporal changes in the WO of Poyang Lake and Dongting Lake. For example, both experienced a decreasing trend in the mean WO (Figure 4) and hydrological connectivity (Figure 8).…”

“…NPP is an important ecosystem service provided by Poyang Lake. Ye et al [22] observed that annual NPP shows a significant negative correlation with water inundation duration in Poyang Lake, and the correlation intensity is far greater than that of the other three influencing factors (air temperature, solar radiation, and precipitation) that control NPP. In this study, we observed that there was a significantly negative correlation between the mean WO and NPP in Poyang Lake.…”

“…Few studies have investigated the landscape structure and ecological impacts of WO in Poyang Lake and Dongting Lake. Landscape structure has a direct impact on the change process of the ecological environment, thus directly affecting ecological functions [22]. Therefore, it is necessary to investigate the landscape structure and ecological impacts of WO.…”

The benefits of the water diversion on a densely populated fragmented lake area — A remote sensing view

“…Therefore, when farmland, dykes, islands, etc, are distributed in or around the lake, the integrality of the lake is destroyed, and the fragmented lake will weaken the connection between the parts. For example, the fragmentation of the lake area of Poyang Lake has increased due to the large area of cultivated land reclamation [18]. Due to the artificial construction of dikes and bridges, East Lake was divided into several sub-lakes [19].…”