Masting Events Deplete Carbon Storage in a Clonal Perennial Herb, <scp> <i>Veratrum album</i> </scp> subsp. Oxysepalum

ABSTRACT The resource budget hypothesis is widely accepted as a physiological explanation of masting, which is characterized by highly variable, synchronous reproduction within a population across years. According to the hypothesis, when resources are depleted by a large reproductive output, it takes more than one year to replenish them. This results in intermittent mass flowering and seed production. The key resources depleted by a single reproduction have been identified in several woody species but rarely in herbaceous species. We examined the adequacy of the resource budget hypothesis for masting in the herbaceous species Veratrum album subsp. oxysepalum and identified the key resources. Over an 11‐year period, we investigated stem volume as an indicator of resource storage level and flowering in 61 individuals, each consisting of a single ramet, tagged in the 2013 mast year in a population in northern Japan. We compared the concentrations and masses of carbon and nitrogen in the aboveground and belowground parts of flowering and non‐flowering ramets. Stem volume decreased in the year after reproduction and gradually recovered in subsequent years. Flowering occurred again once the ramet had grown to a large size. These results support the predictions of the resource budget hypothesis. Flowering ramets had greater concentrations and masses of carbon in their aboveground parts than non‐flowering ramets, but smaller concentrations and masses in their belowground parts. Conversely, there were no consistent differences in nitrogen concentration or mass between flowering and non‐flowering ramets. Therefore, carbon is the key limiting factor in reproduction for this species.