噪声和捕捞对捕食生态系统稳定性的影响

EFFECTS OF NOISES AND HARVESTING ON THE STABILITY IN THE PREY-PREDATOR ECOSYSTEM

讨论了在色噪声激励下,具有独立常数率捕捞和庇护所效应的捕食生态系统的稳定性问题.在弱扰动假设下应用Stratonovich-Khasminskii随机平均原理分别得到了两个物种的稳态概率密度,并研究了捕捞强度E1,色噪声强度Kii,谱宽和噪声相关时间对两个物种的稳态概率密度的影响.Monte-Carlo模拟验证理论求解的合理性.研究表明:1)随着捕捞活动的增大,随机因素对生态系统的影响逐渐减弱;2)噪声强度越大,生态系统越不稳定;3)随机激励的谱带越宽,生态系统越稳定;4)随机激励的相关时间越小,生态系统越稳定.

This paper discusses stability problem of a new stochastic predation type ecosystem with corporating a prey-refuge and independent harvesting in either species. To explore the prey-harvesting and colored noises effects on the stability of the ecosystem, with the assumption of weak disturbances, the stationary probability den- sity functions for both species were obtained by applying the Stratonovich - Khasminskii averaging principle. The accuracy of the results obtained from theoretical method was demonstrated by those obtained from Monte Carlo simulation. Results obtained show that： 1 ） the ecosystem with smaller harvesting is less stable when the system is disturbed by noises; 2） the stronger the noise intensities are, the less stable the ecosystem will be; 3） the narro- wer the band width is, the less stable the ecosystem will be; a narrower band width leads to a less stable system; 4） a smaller correlation time leads to a more stable system.