Distribution of Decline of Momi fir (Abies firma) in Mountains of Western Tokyo.

概要

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In order to determine the distribution of <I>Abies firma</I> (Momi fir) decline in mountains of western Tokyo, 107 sites (618 specimens) were studied from 1992 to 1993 to evaliate the decline. Total decline index which summed up variables of twig death, crown density, crown form and vigorousness was effective as a criterion for the survey. The percentage of declining trees, whose rank was 2 or more regasding twig death and crown density, was 45.2%, and 45.6% respectively. The decline of <I>Abies firma</I> was unrelated to geographical factors, that is, slope classification and valley density. On the other hand, there was a correlation between the decline and longitude and latitude of the sites, indicating a decline in the southeastern area and slightly damaged area in the northwestern mountains of Tokyo. But there was severe fir decline in a part of the valley located in the northwestern area. Concerning altitude, the decline was severe in low regions of 250 m or less in altitude, and healthy at high altitudes. However, even at altitudes of 750 m or more a slight decline of 57.9% was observed.
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