内外噪声扰动下放牧生态系统的稳态转换现象

Regime Shifts in Grazing Ecosystems with Internal and External Noise Disturbances

生态系统的稳态转换可能会造成生态环境的退化和巨大的经济损失,研究稳态转换如何受随机因素影响非常必要.文章研究放牧模型在高斯噪声和Lévy噪声共同作用下的稳态转变现象.首先介绍了放牧模型的确定性方程,然后利用Janicki-Weron算法产生Lévy噪声,并通过四阶Runge-Kutta算法对放牧系统进行数值模拟,最后基于稳态概率密度分别分析了内噪声和外噪声对系统稳态转换行为的影响.研究发现两种噪声均可诱导系统产生稳态转换现象,但作用相反;高斯噪声强度的增大可以诱导放牧系统从高植被态向荒漠态转换,而Lévy噪声的强度、稳定性指标和偏斜参数的增大均可促进放牧系统从荒漠态向高植被态的恢复.

Regime shifts in ecosystems can cause degradation and severe economic losses,hence it is critical to discuss how steady-state shifts are influenced by stochastic factors.In this paper,We investigate the phenomenon of regime shifts in the grazing model under the combined effect of internal Gaussian noise and external Lévy noise.Firstly,we show the deterministic equations of the grazing model in detail,then Levy noise is generated by Janicki-Weron algorithm,the grazing ecosystem is obtained by using fourth-order Runge-Kutta method.Finally,we analyze the influence of the internal and external noise parameters on the regime shifts separately based on steady-state probability densities(SPD).It is found that both Gaussian noise and Lévy noise can cause the regime shifts phenomenon but with opposite effects.The increase in Gaussian noise intensity enhances the likelihood of regime shifts from high vegetation state to the desert state.While the increase in Lévy noise intensity,stability index and skewness parameter enhances the likelihood of regime shifts from the desert state to the high vegetation state.