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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-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)。在湖泊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-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,湖泊生态系统在长期震荡后崩溃。
Compared with terrestrial ecosystems, the response of aquatic ecosystems to global warming is sensitive and vulnerable. Poyang Lake is the largest freshwater lake in China. In recent years, lake water level has dropped and lake beds have dried up frequently. A series of aquatic ecological disasters and ecosystem degradation have taken place. However, the process of ecological change and lake ecosystem disasters caused by climate change And the mechanism is not yet clear. Based on the principle and structure of Lotka-Volterra dynamic model, this paper first builds the competition pattern of phytoplankton (algae) and higher aquatic plants (grass) in primary lakes, and then constructs the predation of primary producers grass, algae and top prey fish Finally, the principle of mass transfer of climate-lake water and ecological factors is used to form the kinetic equations of climate and ecology, and the experimental schemes in different periods of modern and historical periods are set up for numerical simulation. The simulation results showed that the biomass of algae, grass and fish communities in Poyang Lake underwent a stable and quasi-circulatory system during the annual and inter-annual biomass changes under the respective environmental capacity, growth rate and interdependence / suppression (Experiment Ⅰ). In the interaction between lake water and ecological factors, the ecological effects of water volume can maintain the dynamic balance of ecosystems (Experiment Ⅱ). Applying to the lacustrine ecosystems over the past 1,000 years, simulations have found that the lake biomass increases and decreases in an unbalanced rate under the climatic-water change boundary conditions (Experiment III). The feedback of water volume can slow down biomass in the increased stage and speed up the decay stage, thus quantifying the negative feedback effect of climate water changes in the ecosystem. Experiments IV to set up a small-ice age climate show that lacustrine ecosystems oscillate and decline within 600-700 months with a reduction of 19% in precipitation, 33% in lakes and 7% in lakes. When this extreme climate lasts more than 600 months, the aquatic community system collapses completely. Evidence from pollen deposition of sediment-replacement of aquatic and wetland vegetation in the Poyang Lake during the Little Ice Age validated this model to show that under extreme drought conditions, the boundary conditions significantly outweighed the resilience of the ecosystem, and that of the lake ecosystem After long-term turmoil collapsed.