Impacts of water level fluctuations on substrate environments of lakeshore zone of the lakes in the middle and lower reaches of the Yangtze River

Abstract

以长江中下游湖泊为对象,研究了水位波动对湖滨带底质环境的影响.结果表明,底质环境参数沿高程梯度变化明显.底质含水率沿高程梯度增加而减小,pH值沿高程梯度变化不大,有机质、总氮和总磷沿高程梯度呈先增大后减小的趋势.底质环境参数的季节变化也较大.分析表明,水位波动幅度、淹没深度、高水位持续时间等对湖滨带底质环境有较大影响.在中等波动幅度下,底质参数沿高程的变异系数最大,表明此时湖滨带底质异质性较高.夏季湖滨带淹没时间越长、淹没深度越大,底质养分流失越快.高水位持续时间越长,底质pH值变化就越大、营养盐流失越快.本研究结果可为湖滨带生态修复及管理提供依据.;The present paper dealt with the impacts of water level fluctuations on the lakeshore substrate environments of the shallow lakes in the middle and lower reaches of the Yangtze River. The results showed that substrate environments changed greatly with the elevation gradients. Moisture contents of substrate decreased as the elevation increased, and pH value changed little, while contents of organic matter, total nitrogen and total phosphorus in substrate increased at first and then decreased. Also, substrate environments showed clear seasonal dynamics. Analyses showed that the amplitude of water level fluctuations, submergence depth, and duration of high water level had great impacts on the substrates. The coefficients of variation of substrate parameters were the largest in the medium amplitude, indicating that the highest heterogeneity of substrate occurred under such a condition. Substrate nutrients would be lost at an increasing pace with the increase of time and depth submerged during summer. If the duration of high water level was long, the pH values would be changed greater and the nutrients would be lost faster. Our results offered a scientific foundation for ecological restoration and management of the lakeshore.