Environmental variation and forest dynamics in the terrestrial regions around the Sea of Okhotsk

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We made re-measurements (stem diameter, tree height, mortality, recruitment, photosynthesis, chlorophyll fluorescence) of trees (Larix cajanderi, Betula platyphylla), in the three boreal forests with different successional stages in Kamchatka, Russia, that we established 3-5 years before. The number of Larix seedlings per ha was almost constant irrespective of successional stage. The photosynthetic rate of Larix was higher than that of Betula. The degree of photooxidative stress in the photosynthetic system (which is magnified by low temperature and/or low precipitation) was smaller in Larix than in Betula. Betula produced a larger number of seedlings than Larix but the mortality rate got higher than Larix as succession proceeded. At the same time, Betula produced a large number of trunk suckers at the base of the mother trunk as clonal growth. These results suggest that Betula has advantageous reproductive and survival strategies at the early-successional stage, while Larix has those at the late-successional stage. Therefore, we conclude that Larix can be a dominant species in the Kamchatka boreal forest while Betula can form an early-successional forest under stressful conditions (low temperature, low precipitation) after large-scale disturbance such as forest fire in Kamchatka.