Seed production of four shrub species, Viburnum furcatum Blume ex Maxim., Lindera umbellata Thunb. var. membranacea (Maxim.) Momiyama, Magnolia salicifolia (Sieb. et Zucc.) Maxim. and Hydrangea paniculata Sieb. et Zucc. was investigated in a 0.5 ha (50 m×100 m) plot set in a climax beech forest, during three years from 1995 to 1997, by directly counting the number of fruits or infructescences borne on stems. Size and weight of seeds and fruits were also compared among these species. Three species, Viburnum furcatum, Lindera umbellata var. membranacea and Magnolia salicifolia, bear sap fruits or sap fruit-like seeds of a similar size, each of which contains one seed of a similar size, although only Hydrangea paniculata bears much smaller seeds of the wind-dispersal type. The mean size of the fruiting stem was largest in Hydrangea paniculata, followed in order by Magnolia salicifolia, Viburnum furcatum and Lindera umbellata var. membranacea. Every species showed a patchy pattern of seed production in the plot. Seed production was spatially overlapped within the same species among different years, but spatially separated among different species. No spatial correlation of fruiting stems with a particular phase of stand development (gap, building and mature phases) was found for Lindera umbellata var. membranacea and Viburnum furcatum. Three species, Viburnum furcatum, Lindera umbellata var. membranacea and Magnolia salicifolia are considered to be understory shrubs which are adapted to shaded and litter-rich environments, whereas Hydrangea paniculata, being a pioneer shrub, is adapted to open environment or disturbed site.
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