Spatiotemporal predictive models of Mediterranean vegetation dynamics

Empirical modeling of vegetation dynamics can be used for predictive purpos es. The goal of the present study is to construct and evaluate possible app roaches for empirical modeling of vegetation dynamics, and to investigate t heir potential use in planning and management. An empirical model of mediterranean vegetation dynamics was constructed usi ng a case study of vegetation change in an area in the Galilee mountains, n orthern Israel, between 1964 and 1992. Present vegetation in any location w as modeled as a function of past vegetation and environmental factors (e.g. , topography and various disturbances); future vegetation was then modeled as a function of current vegetation and effects of environmental factors. I n order to assess model performance, we compared the actual vegetation map with maps representing model realizations for the study area and for an ext ernal validation area. Three types of measures were used to compare the pre dicted and actual vegetation maps: overall vegetation composition, pattern indices, and cell-by-cell match. We compared the performance of logistic vs . linear models and of stochastic vs. deterministic realizations of a logis tic model. Our results indicate that landscape scale vegetation dynamics can be fairly well modeled using a few biologically important variables. The logistic an d linear models had similar performance, in spite of the reduced informatio n on which the logistic models were based. The use of only a 4% sample of t he database resulted in a negligible reduction in model performance. Model performance was reduced, but was still fair, when applied to an external ar ea. The merits and Limitations of this modeling approach are discussed in c omparison with other approaches for modeling vegetation dynamics.