极端洪水作用下升金湖消落带生境变化对越冬水鸟群落结构的影响

Impact of habitat changes in the riparian zone at Shengjin Lake under extreme flooding on the community structure of wintering waterbirds

水鸟是湿地生境质量的重要指示性动物类群,可敏感地反映湿地环境变化。浅水通江湖泊消落带具有复杂多样的生境和丰富的食物资源,是水鸟特别是越冬水鸟的重要聚集区,其食物资源的丰富度和可获得性受水文节律影响。在极端洪水作用下,消落带生境变化对越冬水鸟群落结构及其多样性的影响是一个值得关注的水鸟及湿地生态学问题。选择了具有典型消落带生境的升金湖作为研究区域,对2019年(正常水位)和2020年(异常水位)两个越冬季水鸟的数量、种类进行调查统计,分析了消落带的生境变化情况对越冬水鸟群落结构的影响。2019年越冬期,记录到水鸟(50984.20±9595.71)只(n=5),隶属7目13科51种;2020年越冬期,记录到水鸟(27923.00±13808.47)只(n=5),隶属7目12科53种。整个越冬季消落带的水鸟种类略增但数量减少,2019年游禽中的优势种为豆雁,2020年游禽中的优势种增加为豆雁和斑嘴鸭,但涉禽中的优势种由白琵鹭、反嘴鹬、凤头麦鸡转变为苍鹭、大白鹭和反嘴鹬。洪水导致的草滩-水域混合区生境面积减小使湿生植物退化,可能是导致以豆雁为主的食苔草水鸟数量大幅度减少的重要原因;因湖水延迟消退,裸露的泥滩面积大幅度下降,可能致使食底栖动物水鸟数量减少;湖泊水位上升和消落带水域面积的增加,加大了食鱼水鸟的捕食难度,导致数量锐减;提供植物种子的生境缺少,使觅食种子的斑嘴鸭和绿翅鸭数量明显下降;沉水植物的适宜生境面积下降直接影响到食地下茎的水鸟分布,并致其数量减少。研究结果有利于理解升金湖消落带生态系统的健康状况,为越冬水鸟的保护和湿地的管理提供基础资料。

Waterbirds are important indicators of wetland habitat quality.The riparian zones of shallow river-connected lakes provide the complex and diverse habitats and rich food resources for waterbirds,especially wintering waterbirds.Hydrological rhythms determine the richness and availability of the food resources for wintering waterbirds.Under the extreme flood pulse,the influence of habitat changes in the riparian zone on the structure and diversity of the wintering waterbird community is a noteworthy problem of waterbirds and wetlands.In this study,we chose Shengjin Lake with typical riparian habitats as research area,surveyed the number and species of waterbirds in 2019(normal water level)and 2020(abnormal water level),and analyzed the effects of habitat changes on the community structure of wintering waterbirds in the riparian zone.A total of 50984.20±9595.71(n=5)waterbirds were counted during winter of 2019,belonging to 7 orders,13 families,and 51 species,whereas only 27923.00±13808.47(n=5)waterbirds were recorded in 2020,belonging to 7 orders,12 families,and 53 species.In the whole winter,the species diversity of waterbirds increased slightly but the number decreased in the riparian zone.In 2019,the dominant species of swimming birds were Anser fabalis.In 2020,the dominant species of swimming birds increased to Anser fabalis and Anas poecilorhyncha.But the dominant species of wading birds changed from Platalea leucorodia,Recurvirostra avosetta and Vanellus vanellus,to Ardea cinerea,Egretta alba and Recurvirostra avosetta.The decrease of habitat area in the vegetation-water mixed area caused by flooding negatively impacted wet plant populations,which might be an important reason for the significant decrease in grass forager number(mainly Anser fabalis).Due to the delayed lake water recession,the area of bare mudflats has decreased significantly,which might lead to a decrease in the number of invertebrate foragers.Water level raise and water area increase in the riparian zone increased the difficulty of predation by fish foragers,resulting in the number of them drops sharply.The lack of habitats providing plant seeds significantly reduced the number of Anas poecilorhyncha and Anas crecca.The habitats suitable for the submerged plants decreased,directly affecting the distribution of tuber foragers,resulting in their number reduction.The study results are helpful to understand the health status of the ecosystem in the riparian zone at Shengjin Lake,and provide basic data for the protection of wintering waterbirds and wetland management.