Research On The Stability Of Stochastic Structure Ecosystem

It is a basic issue that how to maintain long-term coexistence of different species in the ecosystem field.Before the 1970s,ecologists believed that species diversity could promote the stability of ecosystems.The downside is that this view is based on observations that the number of species changes in a simplified terrestrial community,rather than based on observations of different ecosystems.In 1972,May used local stability analysis and stochastic matrix theory to prove that increasing the complexity of the ecological system would reduce its stability.The so-called ecosystem complexity here involves three aspects:the number of species(N),the probability of interspecies interaction(P1)and the mean strength of interaction(O).In fact,the complexity of real ecosystem also contains the diversity of inter-species relationships,such as competition,cooperation and predator-prey.Now,most of the research results assume that there is only one type of interspecies relationship in the system and it is assumed that different species have the same population density when they stably coexist.This is obviously inconsistent with the reality.This article will ignore the above non-ecology hypothesis,and use the local stability analysis method and the permanent analysis method to calculation the influence between the stability of the system and the probability of interspecies interaction,the mean strength of interaction and the diversity of inter-species relationships at different population densities.The results showed that:when the probability of interspecies interaction is invariant,the probability of satisfying local stability analysis condition and permanent analysis condition will reduce with the increasing of the mean strength of interaction.That is to say,the stability of ecological system would reduce;With a certain mean strength of interactions,the stability of ecosystem will increase with the increasing of interspecies interaction probability.In addition,in the purely competitive stochastic structure ecosystem,when the mean strength of interaction is weak,the stability of the ecosystem does not change significantly with the increase of predator-prey probability or cooperation probability;When the mean strength of interaction is strong,the probability of predator and prey is increased,and the stability of the ecosystem decreases first and then increases(when the inter-species interaction probability is strong,the stability of the ecosystem decreases and then tends to be gentle);Increasing cooperation probability,the stability of the ecosystem decreases first and then increases.However,when the mean strength of interaction is at a certain value,the stability of the system will decrease with the increase of the predator-prey.