Effects of canopy gaps on the demography of the subcanopy tree Styrax obassia

. To evaluate the gap dependency of the subcanopy tree species Styrax obassia , we estimated the demographic parameters of this species in a permanent plot in the Ogawa Forest Reserve, Central Japan, a temperate deciduous forest. From the data collected over eight years, we constructed four transition matrix models of Styrax : a whole population; a shaded subpopulation; a gap‐site subpopulation; a compound population of shaded and gap‐site subpopulations. The whole‐population model suggested that the population structure of Styrax is stable in its present condition. The asymptotic population growth rate of the shaded subpopulation was larger than 1, suggesting that this species can maintain its population even under shaded conditions. The elasticity analyses showed the relative importance of survival of adult individuals that stay mostly under a closed canopy. Since the subpopulation in gaps is very small in a mature forest, the contributions of high seedling survival and high fecundity of adult trees in gaps to the whole population growth were smaller than the survival of adult individuals in the shade. Although we showed that this species has the potential to increase its population in larger disturbances, it actually dominates in the study site where the disturbance scale is relatively small. Styrax should be classified as a typical shade‐tolerant species, and it also takes good advantage of small scale disturbance. It can sufficiently maintain its population in a mature forest with small‐scale disturbances and has the adaptive characteristics of species that live under a closed canopy.