| The production of flowers and seeds, seed consumption, and the population dynamics of the major insect and small mammal seed predators of sugar maple (Acer saccharum), yellow birch (Betula alleghaniensis), and beech (Fagus grandifolia) were studied over a three year period at the Hubbard Brook Experimental Forest in New Hampshire.;Density estimates of Peromyscus maniculatus indicated a numerical response to seed resource availability, while densities of two other small mammal species, Clethrionomys gapperi and Napeozapus insignis, appeared to be unrelated to levels of tree seed production.;Beech seeds suffered the greatest losses to seed predators, while losses of sugar maple and yellow birch seeds to both insect and mammal consumers were relatively light. Consumption of seeds by mammals was lowest at the highest levels of seed production, while no consistent relationship was found between the percentage of seeds consumed by insects and seed crop size.;In years of high seed production, the number of germinable seeds produced was more than adequate to provide for regeneration, and differences between years of high and low seed production were accentuated by low percentages of seeds containing embryos during seed failures.;Significant between year differences in flower and seed production were found in all three tree species, and differences in seed production were attributable to differences in flower production. All insect seed predators showed significant changes in densities over the course of the study, and alterations in the life history patterns of these species occurred in response to seed failures. These included a change in the type of tissue utilized in a species of Chionodes (Lepidoptera:Gelechiidae) which fed on beech seeds and stems, extended larval diapause in Laspeyresia candana (Lepidoptera:Oletheutidae) feeding on sugar maple seeds, and deferred reproduction in Apion simile (Coleoptera: Curculionidae), a seed predator of yellow birch fruits.;Seed predators were found to have only a slight effect on tree regeneration. The reason for this is that mast fruiting alternately starves and satiates seed consumers, resulting in relatively low rates of seed consumption.;Several hypotheses for the adaptive value of mast fruiting are considered, and it is concluded that fluctuating seed crops in climax trees are an adaptive trait which has selective advantages with respect to seed predation, the efficiency of pollination, and seed dispersal. |
