Flowering phenology of understory herbaceous species in a cool temperate deciduous forest in Ogawa Forest Reserve, Central Japan

Observations of the flowering phenology and measurements of the heights of understory herbaceous plants were made in a cool temperate deciduous forest , where light availability is relatively low and fluctuates markedly throug h the year, and it is too cold for many plants to grow in winter. Ninety-on e species were recorded between April and October. The number of flowering species as a function of date showed a bimodal distribution. The plants flo wering in spring and those flowering from late summer to early autumn each accounted for about 40% of the number of species. The plants that flowered in spring were smaller than those that flowered later in the season. The sp ring flowering plants would produce flower buds in the previous growing sea son, as the time from the appearance of the aerial part to flowering was tr ansient Some species completed their main life history events during the sp ring as spring ephemerals. The small sizes in these species may result from bud formation in the previous season and/or the short period of growth. Th e plants that flowered in late summer and early autumn, by contrast, were l arge. These plants should have relatively long periods of vegetative growth and flower at the end of the growing season using matter produced in that year. A long vegetative growth period would tend to make plants firm and/or large. It was suggested that flowering phenology was separated into two pe riods by the climatic and environmental constraints of a cool temperate dec iduous forest.