放牧地におけるエゾノギシギシの個体数変動

概要

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This paper offers a demographic treatment of density data acquired between 1977 and 1978 for Rumex obtusifolius L. in grazed grasslands near Sendai city, northeastern Japan. The population density rapidly increased in late spring and summer, and decreased appreciably in autumn (Fig. 1), but the fluctuations in population density were small in comparison with the large number of individuals lost and gained. There was no positive relationship between recruitment and mortality during the study period (Fig. 2). Recruitment was generally high on bare soil areas and at high temperatures during late spring and summer, while the peak in mortality occurred when the pasture was in its most passive growth after summer. There was a different pattern of mortality among the cohorts of individuals established at different times of year (Fig. 4). They had different mortality risks (Fig. 3), and the number of surviving individuals over the period of observation was relatively high in cohorts of earlier emerging individuals when compared with the number of those emerging later (Figs. 5 and 6). Differences in the patterns of mortality depending on age of individuals, time of establishment, presence of associated species, and trampling with grazing behavior were discussed.
日本雑草学会の論文
1991-09-02