Population biology of Aesculus turbinata Blume: A demographic analysis using transition matrices on a natural population along a riparian environmental gradient

Abstract

Population structure and dynamics of a riparian canopy species, Aesculus turbinata (Japanese horse chestnut), were analyzed based on the census data collected for the 8 years from 1989 to 1996 in temperate deciduous forests in Ashiu, Kyoto Prefecture, Japan. The censuses were conducted in three permanently established study plots over an environmental gradient that included the lower hill slope, river terrace, and floodplain of a riparian area within a forest stand of approximately 3 ha. Transition matrix based on the data from 1989 to 1996 was provided for the total population made by pooling population data from all subpopulations in three different habitats (i.e. slope, terrace, floodplain). The total Aesculus population showed positive population growth (λ = 1.0298). From the elasticity analysis, larger elasticity values were obtained with increasing size‐ or stage‐classes. A combined transition matrix was also constructed for the life‐history processes consisting of three subpopulations developed on an environmental gradient. This whole population linked by seed flow showed an increase in population size (λ = 1.0286). The elasticity matrix showed the relative importance of the slope subpopulation, suggesting its significant role as a mainland source population. Log‐linear analyses were carried out to examine spatiotemporal variations of life‐history parameters; significant effects of stage and plot were recognized, while no effect of year was detected on any life‐history parameters except for fecundity.