The Modeling And Application Of Niche And Community Based On Type-2 Fuzzy Sets

How to model and quantify the niche and community is a fundamental problem in ecosystem. The stability of community and ecosystem is one of the hot question need to be concerned. In this paper, we focus on the complex nonlinear ecosystem and model the niche and its relatives by fuzzy set theory. We believe such model would be a unification of three common famous niche models. Due to the broad band effect inherent in type-2 membership function and the ability of describing the higher uncertainties, we construct the dynamic niche model, which combines the spatial structure and functional character together. Moreover, it could reflect the dynamic progress of realized niche changing between ideal niche and fundamental niche. With our proposed model, the model of measurement, community and some relatives are also constructed.In addition, we proposed the relationship principle of niche and community by theorems in fuzzy set theory, studied the hiberarchy and horizontal pattern of community, and demonstrated Shelford's law of tolerance and Gause axiom. In this way, we primarily construct the mathematical theory frame of three common niche models, which would be a new method for describing the complexity in ecosystem. By the parallel connection structure of type-2 fuzzy logic system, we put forward a mathematical model of redundancy structure and design method of system. Furthermore, neural network and genetic algorithms are used to optimize the design. Therefore, we compute the reliability degree of community and of each layer, study the stability of community and the relationship between evolution and environment transformation, investigate the adaptive, robust and fault tolerance in evolution and the corresponding model is proposed. We then apply the model to the animal and plant community. Results indicate that our method not only show the same result with former methods but also provide more biological information. For instance, it reflects the diversification degree of utilization of resource and implies the species' exploitation for the bound and tolerance for the environment under the influence of environmental factors.