Large-area Mapping of the Mass Mortality and Subsequent Regeneration of Abies mariesii Forests in the Zao Mountains in Northern Japan

Abstract

Mass mortality caused by bark beetles occurred locally in a subalpine fir (Abies mariesii) forest in the Zao mountain area in northern Japan. We examined the distribution of the mass mortality of A. mariesii trees and the corresponding locations to analyze the mortality rate in each section of a 50 m mesh, using satellite images and GIS, in a 528 ha fir forest in Yamagata Prefecture. Our results show that there were three areas where sections with mortality rates of 60％ or more were concentrated in this study area. They were located on western slopes with high altitude. However, since there were still many sections with low mortality rates in these locations, the local occurrence of mass mortality could not be explained by location alone. Sasa bamboo (Sasa kurilensis) dominates the forest floor in many fir forests. Study plots with higher sasa coverage had fewer juvenile A. mariesii trees. Sasa coverage tended to increase as altitude increased, and there were no A. mariesii seedlings and saplings in the plots at high altitudes. This tendency was extremely noticeable on the western slope of Mt. Jizoudake, which was also the area in which sections with high mortality rates were most concentrated in this study area. Therefore, mass mortality forests dominated by sasa at high elevations are predicted to be difficult to regenerate because they have few juvenile trees on the forest floor.