林齢の増加に伴うスギ林花粉生産量の変化

抄録

In order to determine changes in the annual production of pollen by Sugi (Cryptomeria Japonica D. Don) stands with increasing age, five stands ranging in age from a planted 37-yr-old stand to one about 600 yr old in the grounds of a Buddhist temple were studied. Pollen production rates were estimated from the number of fallen male flowers in a stand by the litter trap method and the quantity of pollen per flower sampled before anthesis. The relationship between the number of fallen male flowers in a atand and stand age showed a ceiling curve, indicating a constant upper limit for several hundred years after the age of 50 yr. This minimum stand age of 50 yr, after which a constant value of pollen was produced, was quoted from findings obtained in our previous study. The data indicate that an increase of pollen dispersal per unit land area if the final cutting age of Sugi forests is increased to as much as 120-150 yr is improbable. In 1990, the production rate in the five study stands was estimated to be 4.3-52×10^<12> pollen grains ha-<-1>yr^<-1>, or 43-360kg d. w. ha^<-1> yr^<-1>,