Modelling the masting behaviour of Betula platyphylla var. japonica using the resource budget model

A masting model of Betula platyphylla var. japonica, a major wind-pollinated tree in Hokkaido. northern Japan. was constructed from the perspective of the resource budget model. An 11-year data series of pollen dispersal by birch showed marked annual fluctuations in flowering. Although flowering fluctuated widely among years, a reciprocal relationship was observed between two consecutive years; very little flowering occurred after a mast year, This suggests that there is a negative relationship between current fruiting and flower bud induction. There was a significant positive relationship in flowering between regions, which suggests that weather conditions regulate flowering in birch, A model that included weather variables and resource allocation systems among years explained 94.5% of the observed annual fluctuations in flowering. In the model, warm spring conditions from bud burst to flower bud development and little flowering in the previous year (t-1) resulted in increased flowering in the current year (t), whereas abundant flowering in year t-2 resulted in a decrease in flowering in the current year (1), The latter indicates that flowering in year t-2 affects resource storage after overwintering, the balance is carried forward to year t-1 and affects the initiation of flower primordia before bud burst. In the model, fluctuating weather conditions in the previous spring strongly affected the masting behaviour of birch. (C) 2001 Annals of Botany Company.