Modelling forest dynamics with vital attributes and fuzzy systems theory

Vital attributes are the minimal autecological characteristics required to predict the behavior of plants in disturbed environments. In this paper, I modify the existing classifications of reproductive method, establishment requirements, and disturbance resistance to better simulate the behavior of complex vegetation. The vital attributes are coded into a stochastic simulation model for analysis of successional development and disturbance response with varying fire return interval and fire severity. The vegetation composition and dynamics are analyzed with fuzzy systems theory, a fuzzy set generalization of dynamical systems theory. The vegetation composition and structure define a fuzzy state space, and the system dynamics are determined by the simulated trajectory through the fuzzy state space. Model output is validated with respect to vegetation patterns of southwestern U.S. Sensitivity analysis of the model behavior with varying vital attributes is used to analyze the ecological characteristics appropriate to plants in disturbed environments, and implications of the model for plant community diversity are also analyzed.