| Research Abstract |
(1) The tree limit on Mount Fuji is mainly composed of larches (Larix kaempferi) that are the dominant forest species there. The limit ranges from 1,400 to 2,900 meters, depending on the slope. On the western and northwestern slopes of Mount Fuji, where the forest vegetation reaches a high altitude, we have investigated the altitudinal changes of larch growth, e.g., tree height, diameters at breast height and ground level, burried seed number, and tree age. They were compared with some environmental factors, especially thermal condition. We have attempted to reconstruct the climate during the tree limit ascending. As a result, the time period during which a tree limit ascends seems to be identical to the period during which low-growth periods, that is, low-temperature periods occur frequently. (2) In order to examine the summer thermal conditions over the mountainous regions of central Japan, oserved mountain-air temperatures were compares with free-air temperatures. The average temperature differnces (mountain-air minus free-air) appear positive in the central region, and negative in the outlying areas of the mountains. During the summer, especially when the Ogasawara high extends over the Japan Islands, the positive temperature difference in the central mountainous region becomes more prominent. Some effects of this thermal characteristic to the subalpine forest have been studied. (3) The tree ring data of a Japanese red pine (Pinus densiflora) in the montane regionof Nagano Prefecture, central Japan, were examined. As a result, It was proved that this tree was established more than 235 years ago, and there were the low-growth period corresponding to the Little Ice Age of the 1800's.
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