摘要
where γ（v） = a（v- b）<sup>2</sup> + c with positive a, b, c. As a simple mathematical model ofmono-species forest with two age classes it takes account of seed production and dispersal,where u denotes the density of "young" tree, v denotes the density of "old" tree, and ω de-notes the density of air-borne seeds; α,β,δ and d are seed production, deposition, establish-ment and diffusion rates respectively; f and h are coefficients of aging and mortality of "old"tree respectively. （1）<sub>p（t）≡0</sub> was first presented and was then reduced to a lower-dimensionalreaction-cross-diffusion model to study travelling wave solutions in ref. [1]. We assume herethat p （t） is a periodic function of period T and 0≤p（t）≤p<sub>M</sub>, considering the seasonal ef-fects of winds, weather conditions, temperature, etc.. We consider （1） under the initial con-
