Changes in Growth and Reproductive Strategy of Disporum Smilacinum in Canopy Gap and Closed Canopy Areas

Disporum smilacinum A. Gray is a typical monocarpic pseudo-annual plant which is distributed under forest canopy in the East Asia. D. smilccinum reproduces both vegetatively and sexually although its population size is mainly increased by rhizomes. We investigated the morphological characteristics and reproductive strategy of D. smilacinum in gap and under closed canopy sites to evaluate the effects of changes in light condition on the population dynamics of shade-adapted D. smilacinum. Shot densities, number of leaves, number of flowering shoots, shoot length, rhizome length and biomass of individual organs of D. smilacinum were compared between gap and closed canopy sites which were located adjacent to each other. Whole plant biomass, rhizome biomass and the number of flowering shoots of D. smilacinum in gap were significantly lower than those under closed canopy (P < 0.05), while root/shoot ratio in gap sites was higher than that under closed canopy, indicating that canopy gap decreased growth and sexual reproduction of D. smilacinum. Spatial autocorrelation using spatial distribution of morphological characteristics showed that the size of aggregates of individuals with similar morphological characteristics was larger under closed canopy than in gap sites. Increased light by gap brines about stressful condition to shade-Adapted D. smilacinum, reducing growth, population productivity and sexual reproduction.