Species diversity, spatial distribution and protection strategies of wintering waterbirds after extreme summer flood in Lake Poyang

Abstract

鄱阳湖是我国最大的淡水湖，也是具有国际意义的候鸟越冬地. 近年来，鄱阳湖水文情势异常使得候鸟越冬环境更加复杂. 本文以2020年鄱阳湖出现夏季极端水位为背景，基于2019和2020年鄱阳湖越冬水鸟同步调查数据，探讨了夏季极端水位对越冬水鸟丰富度和空间分布的影响. 研究结果表明：夏季极端水位条件下鄱阳湖越冬水鸟的总数量、群落结构和优势物种组成相对稳定，水鸟数量由597307只下降至572358只，主要是鸭科、鸥科、鹳科、鸬鹚科和鹮科鸟类数量明显下降；食块茎、食种子和食鱼集团水鸟数量均有所下降. 水鸟的整体空间分布格局变化不大，主要栖息地仍为鄱阳湖保护区和上饶湿地的碟形湖及人控湖汊，越冬水鸟向人工湿地扩散加剧. 2019年在人工湿地主要记录到灰鹤926只、白鹤3只；2020年则记录到白鹤2215只、灰鹤7294只、白头鹤88只、白枕鹤378只、豆雁550只、鸿雁3100只、灰雁3200只和小天鹅1543只. 2020年冬季人工湿地中的越冬水鸟数量比2019年增加显著. 鄱阳湖夏季极端水位导致沉水植物群落崩溃，造成植食性水鸟在天然湿地中的越冬食物短缺，从而导致种群空间分布格局出现明显变化，这也是鹤类和雁类水鸟前往人工湿地觅食的主要原因. 因此，在夏季洪水频发的背景下加强人工湿地管理，是当前解决越冬水鸟天然湿地食物资源短缺的重要措施.;Lake Poyang is the largest freshwater lake in China and has been an important wintering ground for migratory birds. In recent years, the abnormal hydrological regime of Lake Poyang deteriorated the quality of this wintering ground for migratory birds. In summer of 2020, Lake Poyang experienced extreme water level, which maybe affect the waterbird community structure and waterbird distribution. We compared the wintering waterbird species diversity, abundance and spatial distribution between winter of 2019 and 2020 to understand the impact of extreme water level on wintering waterbirds. The results showed that the total number, community structure and dominant species composition of wintering waterbirds were relatively stable after extreme summer water level. The total number of waterbirds decreased from 597307 to 572358, among which the number of Anatidae, Laridae, Ciconiidae, Phalacrocoracidae and Threskiornithidae obviously decreased. The abundances of tuber eaters, seed eaters and fish eaters were declined. The overall spatial distribution pattern of waterbirds showed little change. Waterbirds mainly inhabited the sub-lakes and controlled lake branches in the Lake Poyang National Nature Reserve and Shangrao wetland. However, waterbirds spread more severely from Lake Poyang nature wetlands to artificial wetlands nearby Lake Poyang. In 2019, 926 common cranes and 3 Siberian cranes were recorded in rice paddies and lotus ponds; In 2020, 2215 Siberian cranes, 7294 common cranes, 88 hooded cranes, 378 white-napped cranes, 550 bean geese, 3100 swan geese, 3200 greylag geese and 1543 tundra swans occurred in these artificial wetlands. The wintering waterbirds in artificial wetlands in winter of 2020 was significantly more abundant than that in winter of 2019. The extreme water level in summer led to the collapse of submerged plant community, resulting in the shortage of wintering food for herbivorous waterbirds in the natural wetlands, which drove cranes and geese dispersed into the artificial wetlands. Therefore, it is necessary to strengthen the management of artificial wetlands under the condition of frequently higher flood in Lake Poyang for wintering waterbirds conservation.