アラメ群落における年級群組成の変動

概要

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The age composition was monitored for the two populations of Eisenia bicyctis delimited by two permanent quadrats, at Tomari-Hama in Oshika Peninsula, Miyagi Prefecture, from August 1983 to December 1986. The population density of the newly germinated plants was largely affected by the sea water temperature during the months from January to July; rate of recruitwent was conspicuously high at low water temperature but low at high temperature. The plants germinated at low water temperature retain dominant population. Yearly rates of extinction by grazing, withering or detachment were estimated to be 70% in the first year, 60% in the second year, 40 to 50% for 2-5 years old populations and 80% for 5-6 years old populations. The population density of newly germinated plants decreased more rapidly in the area with high density of adult plants than in the area with low adult density; it is probably due to the lower level of light intensity caused by the canopy of the adult plants. The E. bicyclis population are usually consisted of small groups of different ages. When the groups of old adult plants in the population are at relatively low density, the groups of younger plants survive well in its population. The population of Eisenia bicyclis is constructed from successively aged individuals, therefore, the populations are adequately stabilized.
日本水産學會の論文