若齢林におけるハンノキの花粉生産と種子生産コスト

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Systems of sexual reproduction and costs of seed production of Alnus japonica STEUD, a pioneer and anemochore tree species, were studied in two young stands. The annual production rates of each component of the sexual organs were measured using 10 litter traps during five consecutive years from 15 December 1982 to 25 December 1987. The rates of pollen production were estimated by multiplying the number of fallen male catkins per stand by the mean amount of pollen per inflorescence before flowering. The fall of male catkins (buds) before flowering showed a marked peak in the period August-late September every year, amounting to 22% to 54% of the total male catkins in Stand A. This late summer fall was thought to be a saving in the investment of photosynthates to the reproductive organs of A. japonica. Annual pollen production rates (by number) for A. japonica were higher than those of other trees. Furthermore, the production rates for A. japonica were the highest of four Alnus species. There was a low P/O (pollen vs ovules by number per ha) ratio compared with the values for other species. The mean annual production rate of reproductive organs, including pollen, during the five years was 1,545 kg/ha・yr for Stand A and 572 kg/ha・yr for Stand G. However, the photosynthates or dry matter necessary for producing a single seed was 12 to 13 mg in both stands. The specific cost, or the ratio of this invested dry matter to a single seed weighing 1.45 mg, was about eight, being larger than the values (2 to 4) in good seed years for other tree species with larger seeds. It is suggested that the cost of seed production for trees with small-sized seeds is large.
日本生態学会の論文
1996-04-25

若齢林におけるハンノキの花粉生産と種子生産コスト

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