DYNAMICS OF FOREST INSECT DENSITY - BIFURCATION APPROACH

Six basic phase portraits differing in character and in the number of their equilibrium behaviour regimes were suggested in the classificati on of forest insect population dynamics. The portraits graphically ill ustrate six types of dynamic behavior of numbers of the system ''phyto phage-entomophage'': two types of stable equilibrium dynamics (station ary and oscillatory) and four types corresponding to outbreaks of mass reproduction-fixed, permanent, reversive and true outbreaks, respecti vely. In this paper we consider the single parameter model, with its p arametric domains realizing a wide spectrum of phase dynamics, both ba sic and transitional. The changes in the phase portraits are accompani ed by the bifurcations in the model. The results of these analyses are in agreement with the ''stability principle of mobile ecological syst ems'' and may supply its parameter substantiation at the model level. (C) 1997 Academic Press Limited.