Impact of hydrological processes on wetland landscapes and wintering migratory birds in a large floodplain lake (Poyang Lake, China)

Hydrological processes are an important factor influencing the wetland landscapes and the quality of wintering migratory birds habitat in Poyang Lake. However, most of the research on a small spatiotemporal scale and there is a lack of studies on the impact of hydrological processes on migratory bird habitats. This study analysed the response of the Poyang Lake wetland landscape to low water levels from 1990 to 2016 and determined the relationship between hydrological processes, wetland landscape characteristics and migratory bird habitats. According to the results, the number of days during the study period when the maximum water level was higher than the current water level (MaxDay) and the average water level from the 40th to 50th day prior to the current day (D50) are two critical factors affecting the area of grassland in Poyang Lake. In particular, a D50 value of 9.5-11.0 m is important for maintaining the grassland area and growth of wetland vegetation. Besides, the water level should not exceed 11 m from mid-late October to early November and should be maintained between 7.58 and 7.97 m in mid-late December that can maximize the habitat area of migratory birds. Furthermore, this study used ecological threshold to propose the optimal inundation period of Cyperus rotundus L. community, Leersia japonica community, Polygonum criopolitanum community, Phragmites australis community, Triarrhena lutarioriparia community, Carex spp. community and Phalaris arundinacea community, which are 124-174, 31-101, 199-249, 65-147, 51-121, 110-190 and 175-253 days, respectively.