著者

塚田 松雄

出版者

日本生態学会

雑誌

日本生態学会誌 (ISSN:00215007)

巻号頁・発行日

vol.31, no.4, pp.371-383, 1981-12-30

被引用文献数

1

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A theoretical examination of pollen dispersal suggests that : (1) in a forested region containing about 40% Cryptomeria japonica trees, 5.0% Cryptomeria pollen is found ca. 10 km away from the source forest ; and (2) an increase to 5.0% from a lower percentage indicates the actual arrival of trees sparsely distributed in the forest within 500 m. After its initial arrival, the Cryptomeria forest shows a logistic increase under climatically near optimal growing conditions. The standard empirical equation for this increase is expressed by p=50.0/(1+14.16 e^<-0.0014t>), where p is Cryptomeria pollen percentage at time t (yr). Combined pollen frequencies against time that are obtained from six bogs become scattered at higher levels, since the carrying capacity for the population is variablea among these sites. However, sigmoid curves of the Cryptomeria increase toward respective asymptotes are essentially identical from the initial rise up to the 25% level. It normally takes about 1,000 years for pollen percentages to increase from 5% to 10%, and an additional 1,500 years to reach ca. 35%. The fact that Cryptomeria increases logistically implies indeed that even when its pollen percentage is low at the beginning of the rise, climatic conditions must already be favorable for maximum growth of the species.