富士山北西斜面御庭付近のカラマツ低木林はなぜ維持されるのだろうか？一御中道巡りの魅力の再認識のために一

摘要

Mount Fuji is a relatively young mountain, which erupted intermittently until 1707. The tree limit on Mount Fuji is composed of larches (Larix leptolepis). The limit ranges from 1,400 to 2,900 meters in altitude, depending on the slope. Around Oniwa on the northwestern slope of Mount Fuji, a larch scrub community is scattered in patches, forming an island, where the tree line is 2,650 meters. All of the larches are severely deformed toward the northeast due to strong winds. Factors maintaining the larch scrub are examined referring to tree size and tree age. Tree size decreases rapidly above an altitude of 2,390 meters on the northwestern slope, where the forest limit is located. On this slope, we can observe both a group of trees showing a stronger tendency toward growth in terms of height and another group growth in terms of diameter. These growth patterns change depending on the altitude; that is, the higher the altitude, the greater the diameter, and the lower the altitude, the greater the height. On the other hand, the relationships between tree size and tree age show a tendency at lower altitudes of older trees having greater heights, and at higher altitudes of older trees having greater diameter, but not heights. These facts suggest that a larch scrub community forms by controlling exposure to the severe environment. This is also in accord with the observation of older trees having greater deformation. It is considered that embolism is a plausible cause controlling tree size, especially tree height, because frost action with severe transpiration frequently occurs on this slope. As a result, a scrub formation would be fixed. This explanation of the growth mechanism of the landscape around Oniwa on the northwestern part of the Ochu-do trail running along the side of Mount Fuji will assist eco- and geo-tourism development on the Ochu-do.