Influence Of Water Level Fluctuation On Temporal And Spatial Dynamics And Habitat Selection Of Tundra Swan In Poyang Lake

Poyang Lake is an important habitat of waterbirds on the East Asia-Australian migration route,and it is also the main wintering area for Tundra Swan in China.In this study,we collected the water level data of the hydrologic station of Poyang Lake in 2015-2018,and analyzed the trend of water level fluctuation in Poyang Lake.In the same time,we monitored the dynamics of population size and distribution of Tundra Swan in Poyang Lake during 2015-2018,and analyzed the influence of water level fluctuation on the population size and spatial distribution of Tundra Swan.The result showed that the numbers of Tundra Swan populations decreased significantly(R~2=0.907,P=0.048),from 65896 in 2015 to 12710 in 2018.There was a significant positive correlation between the number of Tundra Swan in the winter of 2015-2018and the average water level difference between December and January of the following year(r=0.987,P=0.013).And there was a significant positive correlation between the number of small swan populations and the survey of the average monthly water level in 2015-2017(r=1.000,P=0.020).The Tundra Swan had a clustered spatial distribution pattern in winter,but it is not stable,the Tundra Swan was constantly shifting in these lakes.Fluctuations in water levels have allowed lakes to continuously provide food resources for Tundra Swan.The nature reserve System covered the main lakes of the Tundra Swan,and 65.57±19.25%of Tundra Swan wintered in lakes inside the reserves.We used 3S technology to classify the wetland landscape in Poyang Lake and analyzed the influence of water level fluctuation on wetland landscape.The result showed that with the fluctuation of water level,the landscape pattern of wetland in Poyang Lake has changed greatly.The grass land and mudflat increased with the decrease of water level(grass land:r=-0.752,P=0.002;mudflat:r=-0.877,P=0.051),and the water body decreased sharply with the decrease of water level(r=0.972,P=0.000).In the western and southern Lake areas with high topography and complicated terrain,the wetland landscape changes slowly with the fluctuation of water level,while the wetland landscape in the eastern and northern lake areas with gentle terrain changes more violently with the fluctuation of water level.At the same time,we tracked Tundra Swan by satellite tracking technology,and the actual activity sites of the Tundra Swan were obtained.The influence of water level fluctuation on the habitat selection of the Tundra Swan was investigated by analyzing the distribution of the actual activity sites of the Tundra Swan in the habitat of different landscapes and lake bottom elevation.The results showed that under different water level conditions,the Tundra Swan had a high degree of water preference,under the condition of 7.59 m water level,87.38%of the Tundra Swan activity sites were distributed in the landscape of water body.But there was no significant relationship between water levels and preferences(r=-0.789,P=0.211).In the western and southern lake areas,the Tundra Swan prefers the elevation range of the 13-15.9 m,and the bottom elevation of the Tundra Swan activity point decreased with the decrease of the water level.