Forest recovery after intense disturbance by volcanic activity

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We studied distribution and stand structure of a naturally regenerated Larix kaempferi stand on Mt. Komagatake, a volcano on the island of Hokkaido. Further, biomass allocation, dynamics of shoots, and seasonal changes of water potential were examined in saplings of L.kaempferi and some broadleaved trees. The stands on the mountain were composed of L.kaempferi, Betula spp. and Populus maximowiczii, and assortments of others. At 500m a. s. 1., the stand dominant height was 2.0 to 6.1m and basal area at ground level was 0.1 to 7.8 m^2/ha. These values indicate that the stand intensively restricted growth. The stands at higher altitudes were less developed than at lower altitudes in dominant height and basal area. The present L.kaempferi gradually started being established in the area between 500 and 700m a. s. 1. during 20 to 50 years after the eruption in 1929. Thereafter the number of the established L.kaempferi increased remarkably. We believed that seed dispersal from artificial forests of L.kaempferi that have been planted since 20 years after the eruption, and from the individuals that had invaded in the very early period, contributed to the increase of L.kaempferi trees. L.kaempferi allocated more biomass to leaves than broadleaved trees and less to roots which, however, had a larger ratio of fine roots. Although almost all of the shoots of L.kaempferi survived the growing season, broadleaved trees showed considerably high mortality ratios of shoots. These traits enable L.kaempferi seedlings to establish and to growth favorably. We considered that broadleaved trees could have persisted their population by sprouting. From the results of examining water potential of trees, we regarded L.kaempferi as a drought-tolerant tree, which can maintain physiological ability even under the low water potential, however, P.maximowiczii can be regarded as a drought-avoiding tree which tend to retain high water potential to sustain favorable physiological activity