摘要
与陆地生态系统相比，水生生态系统对全球气候变暖的响应敏感而脆弱。鄱阳湖是我国最大面积的淡水湖泊，近年来湖泊水位下降、湖床干涸频发，发生了一系列水生态灾害事件以及生态系统的退化，但气候变化对湖泊生态灾害发生和生态系统退化的过程和机制目前还不清楚。本文基于Lotka—Volterra动力模型的原理和结构，首先构建湖泊初级生产者浮游植物（藻）与高等水生植物（草）的竞争模式，其次构建初级生产者草、藻与顶级猎食者鱼的捕食模式，最后利用气候一湖泊水量与生态因子的物质传递原理，构成气候与生态的动力方程组，设置现代和历史不同时期的试验方案进行数值模拟研究。模拟结果表明，鄱阳湖藻、草、鱼生物群落在各自的环境容纳量、增长率和相互依存／抑制关系下，年内和年际生物量变化构成了稳定和准循环系统（试验I）。在湖？白水量与生态因子相互作用中，水量生态效应可保持生态系统的动态平衡（试验Ⅱ）。应用到过去1000年湖泊生态系统中，模拟发现在气候一水量变化的边界条件下，湖泊生物量增加和减退的速度不对称（试验Ⅲ）。水量的反馈可使增加阶段的生物量速度减缓、使衰减阶段的速度加速，从而量化了气候水量变化在生态系统中的负反馈效应。设置小冰期气候的试验Ⅳ模拟表明，在流域降水减少19％、湖泊面积减少33％和湖泊水量减少7％的状况下，湖泊生态系统在600～700个月内振荡并衰退。当这个极端气候持续600个月以上，水生群落系统全面崩溃。小冰期中鄱阳湖的沙生和旱生植被替代水生和湿生植被的沉积孢粉证据验证了这个模拟，表明在极端干旱条件下，边界条件变化显著超过了生态系统的应对能力，湖？自生态系统在长期震荡后崩溃。
Comparing to terrestrial ecosystem, lake ecosystem responding to global climate warming is more sensitive and vulnerable. Poyang Lake is the largest fresh-water lake in China. Although the lake is located in a catchment within the subtropical region （25 ° -30°N） , changes in the temperature are lower than the lake water volumes. The highest water level on the multiple annual records is 21.7m a. s. 1. with the lake area more than 3280km2 ,while the lowest water level is 5.9m a. s. 1. with the lake area lower than 146km2. The aquatic biomes are significantly affected by variations of the seasonal and interannual water changes. The lake levels have decreased and the lake bed has become drying recently, leading to numbers of water hazard events and aquatic ecosystem deterioration. However, it is not clear for the processes and mechanism of ecological hazards and ecosystem involution under the climate change. Based on principles and structures of Lotka-Voherra dynamic model, this paper firstly built a competition system between phytoplankton algae and higher aquatic plant of the lake primary producers. Then a predator-prey system was constructed between top-level predator of fish and the primary producers in the lake ecosystem. Finally, based on relations between climate-lake water and the biomes,Lotka-Voherra competitive and/or predatory systems were established with delay functions and feedback controls. Four experiments of different periods, from the modern time to the past 1000 years respectively,were designed to perform the numerical simulations. Data,parameters and coefficients used in the simulations were based on our digitizing, compiling and analyzing the data that were published between 1988 and 2013 from Poyang Lake and the catchment. The simulations showed that biomass variability of algae, aquatic-plant and fish biomes can arrive an equilibrium state in Exp. l, which reached a stable and cycling processes with their environmental carrying capacities, increase rates of the biomass, and competitive
出处
《第四纪研究》
CAS
CSCD
北大核心
2013年第6期1148-1159,共12页
Quaternary Sciences
基金
国家重点基础研究发展规划项目(973项目)(批准号:2012CB956103和2013CB956501)
中国科学院创新团队国际合作伙伴计划项目(批准号:KZZD-EW-TZ-08)共同资助
