Investigating spatiotemporal dynamics of Lake Poyang wetland for the recent century

Abstract

鄱阳湖是我国最大淡水湖和长江中游仅存的两个通江湖泊之一，重建其近百年自然通江的湖泊湿地演变过程，对于鄱阳湖湿地生态修复与保护具有重要意义.本研究基于两期历史时期地形图和遥感产品，构建了1930s、1970s、1990s、2000s和2010s鄱阳湖湿地格局变化数据集，探究了土地利用方式改变和水文连通变化对鄱阳湖湿地变化的影响.结果表明：鄱阳湖湿地面积由1930s的5024.3 km²下降至2010s的3232.7 km²，近百年损失率高达35.7%，其中1930s-1970s时期面积变化最为显著，损失率达33.2%，且主要集中分布于赣江与饶河的入湖尾闾地区和南部康山圩.湖泊湿地向耕地的转移是鄱阳湖湿地丧失的主要形式，1930s以来，共有累计1149.6 km²的湖泊湿地受垦殖的作用转变为耕地.闸坝与圩垸导致的水文连通性降低加剧了鄱阳湖自然通江的湖泊湿地格局的变化.相较1930s，累计有683.4 km²的湖泊湿地与主湖相阻隔，水文节律完全独立于通江水域.基于地统计学的水文连通函数曲线也表明，近百年来鄱阳湖的横向和纵向水文连通性均呈现一定程度的下降，且在1990s以后保持相对稳定的状态.本研究能够为鄱阳湖乃至长江中游湖泊湿地生态修复与生态系统服务提升提供参考状态与客观资料.;Lake Poyang is the largest freshwater lake in China and one of the two remaining lakes freely connected with the Yangtze River in the middle reaches of the Yangtze River. Reconstruction of the spatiotemporal dynamics of the lake-wetland that are freely connected with the Yangtze River for the recent century is of great significance for Lake Poyang wetland restoration and protection and ecosystem services promotion. The present study used two periods of historic topographic maps and remote sensing products to reconstruct the Yangtze connected lake-wetland dynamics database covering the 1930s, 1970s, 1990s, 2000s and 2010s. Impacts of land use changes as well as hydrological connectivity changes on lake-wetland dynamics were explored. Results showed that Lake Poyang wetland area decreased from 5024.3 km² in the 1930s to 3232.7 km² in the 2010s, with a loss rate of 35.7%, of which most of the loss occurred between the 1930s and 1970s, with a loss rate of 33.2%. The lake-wetland loss is mainly distributed in the tail of Gan and Rao Rivers and the Kangshan polder. Moreover, a total of 1149.6 km² of lake-wetland has been converted into cultivated land due to reclamation since the 1930s, which is the main land use change type of lake-wetland. In addition, compared with the 1930s, a total of 683.4 km² lake-wetland was separated from the main lake, from which the hydrological rhythm was independent since then. The geostatistical hydrological connectivity curve of different historic periods also indicated that both the horizontal and longitudinal hydrological connectivity decreased for certain extent for the past century and remained relative stable since the 1990s. This study could provide reference states and data basis for the ecological restoration and ecosystem service promotion of Lake Poyang and even for the middle reaches of the Yangtze River.