Effects Of Landscape Changes And Agricultural Activities On The Community Structure Of Wintering Waterbirds At Shengjin Lake

Suitable lake habitats played an important role on the stability of waterbirds community structures.Abundance,availability of food and human disturbance are important factors affecting the structure of waterbird community.The change of foraging habitat affected the composition of waterbird foraging guild,and then affected the stability of waterbird community structure.Anhui Shengjin Lake National Nature Reserve has experienced habitat degradation due to the development of agriculture(fishery)industry.The lake habitat has been gradually restored by measures such as demolition of fences,prohibition of fish farming,crop compensation,and restoration of aquatic vegetation.In this study,we combined remote sensing image and wintering waterbird data,analyzed the impact of purse seine culture,reclaim land from lakes and polder landuse pattern on the community structure of wintering waterbirds at Shengjin Lake.The main results are as fellows.1.Enclosure and reclamation of lake changed the wetland landscape of Shengjin Lake,as a result of fishery pond turning into paddy fields.However,returning paddy fields to wetland and dismantling seine promote the restoration of aquatic vegetation.The hundreds of thousands of meters of seine nets divided the Shengjin Lake into several areas,and most of the ponds formed by the cofferdams were converted into paddy fields between 1999 and 2010.Under t:he guidance of the government,since 2017,some of the gullies have been converted to paddy fields and implemented artificial promotion of aquatic vegetation restoration.In 2018,all the purse seines at Shengjin Lake were demolished with the coverage of aquatic vegetation cover reaching 40 percent of the lake area.2.The community composition and guild structure of wintering waterbirds have changed,The total number of waterbirds increased,but the species number of them with increasing to decreasing.A total of 33,775 waterbirds belonging to 41 species,12 families in 7 orders were observed in the winter of 2004.In contrast.38794 waterbirds belonging to 44 species,12 families in 7 orders were found in the winter 2015,and 36 species of 7 orders and 12 families,number of 65,308 in 2019.Among them,2004 and 2015,four biodiversity index of predator guild>digging guild>mudflats pick-up guild>grassland pick-up guild,in 2019,that change to digging guild>predation feeding guild>mudflats pick-up guild>grassland pick-up guild Compared with 2004,predator guild increased by 3 times of bird flock,mudflats pick-up guild populations are relatively stable,digging guild descresed by 82.8%,number of grassland pick-up guild increased 8.4 times in 2015.In 2019,we recorded 50918,55 families and 18 species of swimming bird,and 3 orders 7 families 16 species 14390 of wading birds3.Lake habitat changed significantly as influenced the community structure of the spatio-temporal dynamics of waterbirds.Bean geese(Anser fabalis)and White-fronted geese(Anser albifrons)became dominant species and replaced the Tundra swan(Cygnus columbianus)and Swan goose(Anser cygnoides)and Pintail(Anas acuta).Bean geese and White-fronted geese were found in Chi'an,Sanqianmu and Xiaoxihu in 2014,however,dominant populations in 2015 were been found in Yang'e' tou,Bailianwei,Shegan,Sanqianmu and Shashan.Degeneration of submerged vegetation resulted in sharp decline of shallow water foraging guilds including Tundra swans and Pintails and digging guilds including Swan geese etc.The quantity of herbivorous Anseriformes such as Bean geese,White-fronted geese and Less white-fronted geese from pecking guilds increased significantly due to the formation of vast Carex spp.community in lake beach.Moreover,suitable habitats for some ducks were lost due to the transformation of numerous ponds to paddy fields,which could provide alternative habitats for Hooded crane,Bean geese,White-fronted geese etc.The number of birds such as Oriental white storks,Eurasian spoonbills,ducks,and shorebirds were all increased,and the main distribution sites of these birds also increased.4.Paddy fields became important habitats for wintering waterbirds,and affected the spatio-temporal dynamics of the community structure.In 2004,none of wintering waterbirds were found in the paddy fields;however,in 2015,there were four foraging guilds.Compared with 2015,the number of four foraging guilds in the paddy fields increased,but the species in the predator guild,mudflat picking guild and caotan picking guild decreased in 2019.This shows the degradation of lake wetland habitat forced the wintering waterbird community to gradually shift to the paddy fields which temporarily served as a buffer zone for the lake habitat,and shared the pressure of the lake with insufficient food supply for wintering waterbirds.When the lake habitats were restored,the waterbirds in the paddy field habitat were again attracted back to the lake.