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 through the year, and it is too cold for many plants to grow in winter. Ninety-one species were recorded between April and October. The number of flowering species as a function of date showed a bimodal distribution. The plants flowering 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 spring flowering plants would produce flower buds in the previous growing season, as the time from the appearance of the aerial part to flowering was transient Some species completed their main life history events during the spring 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. The plants that flowered in late summer and early autumn, by contrast, were large. 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 periods by the climatic and environmental constraints of a cool temperate deciduous forest.