随机干扰下多稳植被生态系统稳态转换的时间延迟效应研究

Multiple stable states widely exist in the ecosystem, different steady states correspond to different ecological structures and functions , and can exert different values of ecological services. The multistable ecosystem often shifts between different steady states.As a result,such regime shifts can lead to degradation of ecology and economy. The project utilizes shifts between different steady states in the process of vegetated ecological degradation as the research object, considers the external environmental perturbations and the effect of time delay in the process of system degradation , and establishes a multistable vegetated ecological model containing noise and delay. Based on the delayed Fokker-Planck equation and modified Euler numerical simulation,calculating characteristic parameters of the transition behavior in multistable ecosystems (steady state probability distribution and regime shift time, etc), analyzing the effect mechanism of noise and time delay factors on the warning indicators of regime shifts (including intersection point of regime shift time in two opposite directions,etc) of the ecosystem, exploring the stability and resilience of multistable vegetated ecosystem and revealing the laws of regime shift and vegetated ecological restoration , the implementation of this project depends on the methods of non-equilibrium statistical physics to study complex multistable vegetated ecosystems, utilizes the view of physical phase transition theory to understand the shift mechanism between different steady states in multistable vegetated ecosystems, and provides a reference for vegetated ecosystem restoration.

多稳态现象广泛存在于生态系统中，不同的稳态对应于不同的生态系统结构和功能，并且可产生不同的生态系统服务价值。具有多稳态的生态系统经常会发生不同稳态之间的转换，从而导致生态与经济方面的损失。本项目以植被生态退化过程中的不同稳态之间转换为研究对象，考虑外界环境随机干扰及系统退化过程中时间延迟效应，建立含有噪声和延迟的多稳植被生态系统模型。基于延迟Fokker-Planck方程及改进Euler数值模拟，计算表征多稳生态系统跃迁行为的特征参量(稳态概率分布和跃迁时间等)，分析噪声和延迟因素对该系统稳态转换预警指标(两个相反方向稳态跃迁时间的交点等)的影响机制，探讨多稳植被生态系统的稳定性和恢复力，揭示其稳态转变规律及植被生态恢复。本项目的实施在于以非平衡统计物理的方法来研究复杂的多稳植被生态系统，从物理学相变理论的角度理解多稳植被生态系统的稳态之间转换机制，为植被生态系统修复提供一定的参考。

本项目以植被生态退化过程中的不同稳态之间转换为研究对象，考虑外界环境随机干扰及系统退化过程中时间延迟效应，建立含有噪声和延迟的多稳植被生态系统模型。基于延迟Fokker-Planck方程及改进Euler数值模拟，计算表征多稳生态系统跃迁行为的特征参量(稳态概率分布和跃迁时间等)，分析噪声和延迟因素对该系统稳态转的影响机制。主要研究结果表明：(1) 建立含有噪声和延迟的多稳植被生态系统模型，噪声和时间延迟会致使多稳植被生态系统从植被态向沙漠态转换，并且能增大转换到沙漠态的概率；(2) 在多稳植被生态系统加入周期信号，噪声关联强度以及时间延迟的变化也会增强或削弱共振现象，而且时间延迟会诱导双共振现象； (3) 建立含有色噪声驱动下的植被生态系统，自关联时间，噪声之间的关联强度和关联时间，以及时间延迟也会致使系统的稳态发生转换及增强转化速率；(4) 建立随机干扰湖泊富营养化生态模型，噪声可以诱导湖泊生态系统从富营养态向贫营养态转换，噪声强度可以增强生态系统在贫营养态的稳定性。

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