江湖关系变化下雁类生境格局模拟及雁类种群的响应——以都昌保护区为例

Simulation of habitat pattern and population response of geese under the change of river-lake relationship:a case study of Duchang Nature Reserve,Jiangxi Province

2003年后江湖关系变化导致鄱阳湖湿地秋季快速退水,滩地提前出露,草洲面积不断扩张。1998—2020年环湖调查数据表明:越冬候鸟种群总量稳中有升,但雁类种群数量急剧增加。为分析候鸟生境及数量变化成因,从“水文-洲滩-植被-雁类”耦合关系入手,针对鄱阳湖雁类分布最为集中的都昌保护区,基于水动力模型分析了2003年前后保护区水域、洲滩的动态变化规律,根据洲滩梯次出露的特征,结合苔草(Carex spp.)、蓼子草(Polygonum criopolitanum)两种优势洲滩植物群落的淹水时长建立了反映高程梯度的生境适宜度评价模型(Habitat suitability index, HSI),结合鸿雁(Anser cygnoides)、豆雁(Anser fabalis)及白额雁(Anser albifrons)的数量变化分析了模型的敏感性。结果表明:2003年后,同一高程带洲滩在退水期的出露时间比2003年前提前约30 d, 2003年后相同日期的洲滩出露面积较2003年前增加约一倍。1990—2019年雁类生境适宜度指数(HSI)分值总体呈增加态势。9—12 m不同高程带洲滩的出露时间及其面积占比是HSI分值变化的主要因素。相关性分析结果表明鸿雁、豆雁和白额雁的数量随HSI分值增大显著增加,并呈指数曲线变化。当HSI分值大于0.5时,雁类数量急剧增长,尤其在2017—2019年表现明显,洲滩出露过程与雁类迁飞节律较为匹配是该现象的主要成因,确定了洲滩适宜出露时间窗口期——从9月15日(年内自然日第258天)到11月4日(年内自然日第308天)。提出了江湖关系变化下雁类生境保护的建议。研究可为基于越冬雁类保护的生态水文过程调控方案提供科学依据。

After 2003,the river-lake relation between Poyang Lake and Yangtze River has been changed significantly in autumn.Mudflats were being exposed earlier than before 2003 and the area of wetland plants was increasing.The data from the multi-year survey around the lake from 1998 to 2020 show that the total population of wintering migratory birds is steadily increasing,but the population of geese is increasing sharply.In order to analyze the causes of migratory birds'habitat and population changes,we started from the coupling relationship of hydrology-mudflats-vegetation-geese.Based on the hydrodynamic model-the Environmental Fluid Dynamics Code(EFDC),the dynamic changes of waters and mudflats in the reserve before and after 2003 were analyzed in Duchang Nature Reserve,which had the most concentrated distribution of geese in Poyang Lake.According to the characteristics of cascade exposure of mudflat,habitat suitability index(HSI)was established based on the flooding duration and growth distribution of Carex spp and Polygonum criopolitanum.And the sensitivity of the habitat suitability model was analyzed in relation to the population changes of Anser cygruoles,Anser fabalis,and Anser albifrons.The results showed that after 2003,the mudflats in the same elevation zone were exposed about 30 days earlier during the receding period than before 2003,and the area of exposed mudflats on the same dates after 2003 was approximately doubled compared to the period before 2003.From 1990 to 2019,The HSI for geese showed an overall increasing trend.The exposure time of mudflats and their area shares in different elevation zones of 9-12 m were the main factors of interannual variation of HSI.The correlation analysis showed that the number of Anser cygruoles,Anser fabalis and Anser albifrons increased significantly with the increase of HSI,and showed an exponential curve.When the HSI was greater than 0.5,the number of geese increased sharply,especially in 2017-2019,and the main reason for this phenomenon was that the mudflat exposure process matched the migration rhythm of geese.Therefore,based on the results and discussion,the appropriate exposure time window of mudflat was determined-from September 15(258th day of the year)to November 4(308th day of the year).The suggestions for wintering geese habitat protection were proposed under the change of river-lake relation between Poyang Lake and Yangtze River.The findings of this study can provide scientific basis for the regulating scheme of eco-hydrological process based on the protection of wintering geese.