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[論文] Article

Responses of plants to the length of the growing season were studied in an alpine snow-bed by setting five plots along a snow-melting gradient. Performance and phenology were compared between the plots for five herbaceous species (Peucedanum multivittatum, Primula cuneifolia, Veronica stelleri var.longistyla, Solidago virga-aurea var.leiocarpa andPotentilla matsumurae). Performance characteristics measured were flower height, leaf height, leaf number, flower number and fruit number. In the late exposed plots with short snow-free periods, fruit-set was reduced in many species due to the decrease in flower number and/or the short growing season for fruit development.Veronica stelleri var.longistyla andSolidago virga-aurea var.leiocarpa, which decreased in flower and leaf numbers due to the short snow-free period, were sensitive to the short growing season.Peucedanum multivittatum was vigorous in the late exposed plots, but its slow flowering and fruiting prevented the fruit-set from developing in the last exposed plot.Primula cumeifolia andPotentilla matsumurae, quick flowering species that maintained their flower number throught the snow-melting gradient, were considered the most successful species in late exposed habitats.

Growth periods of Primula cuneifolia ssp. hakusanensis and Fauria crista-galli, the snowbed plants, were shorter than those of most alpine plants. Primula cuneifolia ssp. hakusanensis showed a larger seasonal change of starch than that of sugar content in both aboveground and belowground organs. On the other hand, in Fauria crista-galli sugar content and its seasonal change were always larger than those of starch. A relatively high content of sugar in Fauria crista-galli during the cold season seems to protect against freezing in winter. Winter buds of both species and new roots of Primula cuneifolia ssp. hakusanensis were formed in the cold season. It is suggested that snowbed plants have a specific amylase which is active in severe low temperature.