Michiyasu Yasaka

Masting behavior of Fagus crenata in northern Japan : spatial synchrony and pre-dispersal seed predation

An 11-year study of total seed and seed production in five natural Japanese beech (Fagus crenata) forests in Hokkaido, northern Japan, estimated the spatial synchrony of masting and examined whether variation in annual total seed production resulted in fluctuations in pre-dispersal seed-predator populations. We found less synchrony in total seed production than in sound seed production among sites. The coefficients of variation of sound seeds (1.3–2.1) were greater than those of total seeds (0.8–1.3) in each site. Pre-dispersal seed predation by moth larvae has a major influence on sound seed production in F. crenata. To test whether variation in annual total seed production resulted in fluctuations in predator populations, we examined the relationship between the ratio of current year total seed production to previous year total seed production, and the percentage of pre-dispersal seed predation in the current year. We found a negative correlation between insect predation and the ratio of current to previous year total seed production, suggesting that poor total seed years resulted in a decrease in predator populations. The pre-dispersal seed predators of F. crenata appeared to cope well with up to 10-fold variation in total seed production between years, but when the total seed production exceeded 20 times that of the prior year, the predators were satiated.

Plasticity of flower longevity in Corydalis ambigua

We investigated the longevity of individual flowers of Corydalis ambigua Cham. et Schlecht. during different periods of pollinator activity and at different temperatures. To measure potential (unpollinated) flower longevity of C. ambigua, this study was conducted at forest islands where pollinator visits were scarce. The longevity of individual flowers of C. ambigua indicated high plasticity. The longevity of unpollinated flowers in natural pollination ranged from 2 to 25 days and continuously decreased with the date of flower opening. The temperature increased as the flowering season progressed. Furthermore, the greenhouse transplanting experiment showed that higher temperatures shorten the life span of flowers. The longevity of pollinated flowers subjected to hand pollination of newly opened flowers was shorter than that of unpollinated flowers in natural pollination regardless of the date of flower opening. These results showed that not only high temperature but also pollination shortens flower longevity. We discuss the role of plasticity in flower longevity for C. ambigua in relation to pollination success and reduction in the maintenance cost of the flowers.

Variation in seed production among years and among individuals in 11 broadleaf tree species in northern Japan

AbstractSeed production is the most problematic part of tree regeneration and is the least amenable to control by silvicultural management. Understanding variability in seed production among years and among trees will allow better planning of seed collection for seedling production and natural regeneration. We estimated the extent of variability in seed production among years and within years among individual trees. Specifically, we measured individual annual seed production in 11 woody species in Hokkaido, northern Japan. We analyzed the coefficient of variation (CV) of seed production among years and among individual trees. We used population- and individual-based CVs (CVpt and

Basal area growth and mortality of Betula maximowicziana affected by crown dieback in a secondary forest in Hokkaido, northern Japan

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Proximate factors causing mast seeding in Fagus crenata: the effects of resource level and weather cues

) to estimate the variability in seed production among individual trees. Alnus hirsuta, in which these CVs among trees were maximal, will require further analyses of the spatial patterns of seed production among individual trees. Additionally, we used population- and individual-based CVs (CVpy and

Effect of Thinning on the Natural Regeneration of Broad-leaved Trees in Abies sachalinensis Plantations.

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