The EcologicalSociety of Japan HuaRaax(Jap, J, Ecol.), 31: 371-383, 1981 I. POLLENCR YPTOMERIA DISPERSAL AND.L4POIvrCA LOGIS[[ICD. DON FOREST EXPANSION Matsuo TsuKtxDA,Department qf Botany and euatemory Researeh denter, Uitiversity of PVbshington, Seattle, PPL4 9Slos U.S.A. uI. leorevaMMEptptOp9-f4pt fi tuJkl P t/ :-F ;-JkcW{gde\tyg ・ rgmpreMeentva m za th SYI)OPSiS TsuKADA, Matsuo (Dept. Bot. and Quat, Res. Ctr., Univ. Wash" Seattle, WA 98195 U.S.A.) 1981.

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... ersalandlogistjcforestexpansion,Jap.J.Ecol.,31:371-383. A theoretical examination of pollen dispersal suggests that : (1)in a forested region containing about 40% crJ{ptomeriaJ'apom'ca trees, 5.0% &mptomeria pollcn is found ca, 1O km away from the source forest; and (2) an increase to 5.0 % from a lower percentago indicates the actual arrival of trees sparsely distributed in the forest within 5oo m. After its initial arriva!, the CrMptameria forest shows a legistic increase under climatically near optimal growing conditions. The standard empincal equation for this increase is expressed byp == 50.0f(1-t-14.16e"O・OOi4t), where p is Ct:Mptomeria pollen percentage at time t (yr). Combined pollen frequencies against time that are obtained from six bogs become scattered at higher levels, s{noe the carrying capacity foT the population is variable among these sites. However, sigmoid curves of the C7'Jptomeria increase toward respoctive asyrnptotes are essentia]1y identical frorn the initial rjse up to the 25 % level. It normally takes about l,OOO yeais for pollen peroentages to increase from 5% to lO%, and an additional 1,5oo years to reach ca, 35 %. The fact that CZyptomeria increases logistically implics indeed that even when its poilen peroentage is low at the beginning of the rise, climatic conditions must already be fayorable for maximum growth of the species.