鄱阳湖水位变化对雁鸭类时空动态和越冬行为的影响

Poyang Lake is the largest freshwater lake in China and has been an internationally important wintering ground for water birds. Every year, there were about 300 000 individuals of Anatidae wintering in Poyang Lake. Now, Poyang Lake has been one of the most important wintering grounds for Anatidae in the middle and lower reaches of the Yangtze River. Varying water levels are common in Poyang Lake, but recent years have been a succession of new lows. The dry season of Poyang Lake is getting much longer and happened even earlier. The Three Gorges Dam and climate change were thought as major factors that driving this change. It is significant to know what effects this change would have on the wintering behaviors of water birds, and what measures are effective for protecting them. In addition, the Jiangxi Provincial Government has developed proposals for a dam to be constructed across the outlet to Poyang Lake, where the lake empties into the Yangtze River. Through the planned dam, the water level can be controlled at desired levels in dry season. It is well known that it is in the dry season of Poyang Lake that hundreds of thousands of water birds inhabit in this wetland. The public wonder how the dam would affect the migrating birds..Under the circumstances, it is necessary to know the relationship between the ecology of water birds and water level fluctuation of Poyang Lake. This research project chose Anatidae as subject because it is sensitive to the change of water level. We aim to discover the effect of water level fluctuation of Poyang Lake on the distribution pattern, space use mode, and wintering behaviors of Anatidae; and then assess the potential effect of the planned dam on Anatidae. .In this study, we choose tundra swan (Cygnus columbianus) and swan goose (Anser cygnoides) as subjects, which are dominant bird species and typical swimming birds in Poyang Lake. First, we plan to use systematic field surveys to discover the distribution dynamics of the population of tundra swan and swan goose over time in Poyang Lake across different scenes of water level. Second, we aim to use satellite telemetry to track the movement of 16 tundra swan and 16 swan gooses in the dry season, and analyze their home range size and space use pattern. On this basis, we will make correlation analysis between the distribution dynamics, space use pattern and the parameters of water level to examine whether the water level change would significantly affect the distribution and space use pattern..Thirdly, we plan to use focal animal sampling method to study the wintering behaviors of tundra swan and swan goose, compare and contrast their behaviors in different scenes of water level, and discover the effect of water level change on their wintering behaviors. .Finally, we propose to analyze the key factors determining their space use at multiple spatial scales including landscape, home range, and microhabitat, and to discover their decision-making mechanisms of habitat selection. Furthermore, a spatially explicit habitat selection model will be presented. According to the model, we will predict the variation of suitable habitat availability of Anatidae in different scenes of water level, and assess the potential effect of the planned dam. Our research achievements will be beneficial to understand the relationship between water bird and water level change, and also helpful for making scientific decision on water bird conservation in Poyang Lake.

鄱阳湖是我国最大的淡水湖，也是具有国际意义的水鸟越冬地。每年有近30万只雁鸭类在此越冬，鄱阳湖已成为全球重要的雁鸭类越冬地。近年来，受气候变化和三峡工程的影响，鄱阳湖水位波动加剧，枯水期提前，水位持续偏低，湿地景观变化剧烈。这种水位变化会对雁鸭类越冬行为产生怎样的影响，雁鸭类采用什么生存策略适应多变的环境？针对这些问题，本研究以鄱阳湖雁鸭类优势物种小天鹅和鸿雁为研究对象，通过地面同步调查和卫星跟踪技术摸清它们在不同水位条件下的空间分布格局、活动轨迹和空间利用模式，分析水位变化对雁鸭类时空动态和空间利用的影响；并通过焦点动物观察法研究小天鹅和鸿雁的越冬行为，比较不同水位条件下其越冬行为的差异，分析水位变化对雁鸭类越冬行为的影响；进而，利用3S技术从多空间尺度分析影响雁鸭类生境选择的关键因子，建立生境选择模型，分析水位变化对雁鸭类生境可获得性的影响，评估鄱阳湖水利枢纽工程对雁鸭类的潜在影响。

鄱阳湖是我国最大的淡水湖，也是全球重要的水鸟越冬地。近年来鄱阳湖水文情势发生了明显的变化，越冬水鸟面临一个更加复杂多变的生存环境。本研究以鄱阳湖雁鸭类为研究对象，利用卫星跟踪技术对16只小天鹅、15只豆雁和7只赤麻鸭进行了跟踪定位，结合地面调查，研究了这些雁鸭类物种在鄱阳湖湿地的空间分布动态和越冬行为变化，并分析了水位变化的影响及其作用机制。.卫星跟踪数据揭示了小天鹅、豆雁和赤麻鸭的迁徙路线和迁徙特征，同时也采集到了这些物种在鄱阳湖的大量活动位点信息，包括15852个小天鹅有效活动位点、15126个豆雁有效活动位点和7206个赤麻鸭有效活动位点，这些数据揭示了雁鸭类在鄱阳湖区的空间分布及其动态，以及这些物种在鄱阳湖区的分布热点。进一步的分析表明雁鸭类物种的生境利用受到鄱阳湖水位变化的显著影响。小天鹅是典型的游禽，对水体偏好程度较高。在鄱阳湖水位为7.59m时，87.38%的小天鹅活动位点分布在水体景观中。随着水位的下降，小天鹅活动位点的湖底高程也逐渐降低，往湖中心移动。这是因为鄱阳湖水体面积随水位的下降而显著减小，譬如当水位从20.40m减小到7.59m时，水体面积减小了74.96%。.本研究发现鄱阳湖水文情势异常导致小天鹅和豆雁出现了明显的生境转移。大量的个体离开鄱阳湖天然湿地，扩散到周边的稻田和藕塘等人工湿地越冬。进一步的分析揭示了鄱阳湖水位变化对雁鸭类食物丰富度的影响。雁鸭类食物丰富度受到鄱阳湖水位变化的显著影响，其主要食物（苦草和冬芽）的密度变化与鄱阳湖的秋季干旱和夏季高水位存在显著相关性。苦草密度和冬芽密度随六月份平均水位的增加而减少，并且随上一年十月份平均水位的增加而增加。六月平均水位与上一年度的十月平均水位共同解释了苦草密度偏差的86.9%，冬芽密度偏差的86.2%。其构建的GAM模型能够很好地解释并预测苦草密度和冬芽密度的变化。.三峡工程自2006年运行以来鄱阳湖10月份的干旱已成常态，6月份的水位被抬高，夏季高水位更加频繁。因此，鄱阳湖小天鹅和鸿雁等植食性越冬水鸟食物短缺的风险加大，食物短缺将成为常态。鄱阳湖水利枢纽工程对雁鸭类越冬食物丰富度虽有一定的积极影响，并不能从根本上解决雁鸭类的食物短缺，因为其主要是调控枯水期水位，但沉水植物的生长也受到丰水期水位的显著影响。本研究为鄱阳湖以及长江中下游地区的水鸟保护和水文管理提供了重要的科技支撑。