Seasonal variation in air temperature drives reproductive phenology of entomophilous plants in a cool-temperate mire community

Abstract

Phenological responses of plants to temperature dynamics are receiving attention due to the ongoing challenge with climate change. Most previous phenological studies have focused on flowering phenology rather than fruiting phenology. However, at mid-latitudes, the air temperature periodically changes during the growing period of plants. Hence, cool temperatures early and late in the growing period may affect reproductive success through pollination and fruit-development processes. To evaluate the linkages between reproductive phenology and success, we compared the phenologies, photosynthetic capacities, and fruit-set rates among 25 species within a cool-temperate community in northern Japan. The ambient temperature during the flowering periods of individual species increased with delays in flowering-onset time, whereas the ambient temperature during fruit-development periods was highest for species which bloomed in July. Fruit-set success among species was positively correlated with the ambient temperatures during the reproductive periods and with the photosynthetic capacity. Fruit production of early blooming species was limited by cool temperatures during the flowering period, presumably because of low pollinator activity, whereas that of late-blooming species was limited by cool temperatures during the fruit-development period because of slow fruit-development (i.e., sink limitation). Thus, limiting factors of fruit production varied depending on the flowering phenology of individual species within a community.