Population dynamics of Aster kantoensis based on a multi-layer lattice model

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A multi-layer lattice model was constructed for assessing population dynamics and extinction risk of Aster kantoensis, corresponding to three levels : a whole meta-, regional, and local populations. Seed dispersal was considered at these three levels. For flood characteristics, we changed their scale, frequency, synchronization, and occurrence sites within a region. A local population processes were calculated with a projection matrix based on three stages : the small and large rosettes and the flowerings. Germination rate and establishment of seedling was assumed to decline depending on time after a local open patch emergence by a flood, because of other perennial plants invasion (coverage rate : β). We assumed that no seedlings cannot establish after a certain time (habitat deterioration time : dtime). Parameter values were estimated by field surveys and published records. Extinction risk was calculated as the extinction frequency after 100 years among 100 replicates x 10 series.Simulation results showed that the present model has high descriptive ability and that the parameter values of β and dtime influence greatly on the extinction risk. For spatio-temporal characteristics of floods, the occurrence sites affected on the extinction risk largely and the fixation of the flood sites made the risk high eminently. Using the present model, we could detect important factors that influence largely the extinction risk of Aster kantoensis.