The impact of Poyang Lake water level changes on the landscape pattern of wintering wading bird habitats

Abstract

Poyang Lake is one of the most typical seasonal inflow-outflow lakes in China. The cyclical rhythm of water level changes determines the dynamic variations in the wetland landscape pattern of Poyang Lake, directly impacting the habitat and survival of wintering migratory birds, particularly wading birds, which are most sensitive to these changes. This study employs an Artificial Neural Network (ANN) algorithm to interpret wetland landscapes using the Gao-Fen Satellite Images across 14 different water levels. Methods such as Pearson correlation and linear fitting are used to analyze the effects of water level changes on the habitat of wintering wading birds, aiming to explore scientifically based optimum water level. The ultimate goal is to provide a scientific basis for determining the optimum water level regulation scheme for the proposed Poyang Lake Hydraulic Project. The results indicate that the area and shape of Poyang Lake's wetlands are highly plastic, with landscape heterogeneity decreasing and homogeneity increasing as water levels rise. The habitat area for wintering wading birds shows an inverted "V" shape variation with rising water levels, reaching a maximum of 1796.02 km² at a water level of 9.86 m, which accounts for about 48.40 % of the study area. The water level changes in Poyang Lake significantly impact the landscape pattern of the wading bird habitats (p < 0.01). When 6.83 ≤WL→WLx m, wading bird habitats become increasingly fragmented, with habitat patch type diversity, evenness, and connectivity gradually improving. When WLx→WL≤ 15.46 m, the degree of fragmentation moderates, but the diversity, evenness, and connectivity of habitat patches gradually decrease. At water levels between 8.15 and 13.56 m, the habitat structure for wintering wading birds is complex, with high diversity, large habitat area, and good landscape connectivity, providing favorable food acquisition resources and adequate space for wintering wading birds. Based on the need for wintering waterbird conservation, the proposed optimal optimum water level regulation threshold for the Poyang Lake Hydraulic Project is suggested to be between 8.15 and 13.56 m.