The mechanism of coexistence of the dominant firsAbies veitchiiandA. mariesiiis described in relation to regeneration patterns for climax subalpine forests of the northern Yatsugatake Mountains, central Honshu, Japan. Two mature stand types, pure conifer stands ofAbiesspp., and mixed stands ofAbiesspp. and hardwoods (mainly the birchBetula ermanii), are distinguished. Pure stands are likely to show simultaneous decay, followed by evenaged regeneration of stand-floor seedlings (20 cm tall), which persist only in mixed stands. The more shade-tolerantA. mariesiiis supeior in this type of regeneration, whileBetuladoes not succeed, and mixed stands change to pure stands with time. The fact that two patterns ofAbiesregeneration occur in a certain ratio in the forest is what enables the twoAbiesspecies to coexist. A simple dynamical system model supports this conclusion.
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