Larch plantations cover approximately 4700km2 of the island of Hokkaido and have become the principle forest ecosystem in northern Japan. This study focused on how the environmental and biological factors affect the regeneration of Japanese larch (JL: Larix kaempferi) and hybrid larches F1 (HL: Larix gmelinii x L. kaempferi) by comparing their ecophysiological characteristics of growth patterns (carbon balance, nutrient balance, the source of CO2), especially relative to their root growth. Based on the review, we could forecast which larch species will have dominancy if they co-exist under the same environmental conditions in nature. In all, under relatively good growth conditions (for example full sunlight, 15℃ soil temperature etc.), JL seedlings have a greater growth rate (allocate more biomass and nutrients) than that of HL. Thus, relative higher soil nutrient environment and above 7℃ soil temperature are necessary for the growth of JL. Otherwise, HL will be more competitive than JL for example in cold regions or higher regions since HL will be better able to grow under a low or wide variation in soil temperature, or low nutrient soil conditions. Given the slightly shade conditionsuch as at a gap in the forest, or fertile soil condition, HL may also be dominate since the growth of JL was clearly suppressed under such situation. Moreover, HL allocated more photosynthates than JL under roots inoculated by ectomycorrhizae. But the ectomycorrhizae benefited the growth of both larch species. In this perspective, we should learn more about their interactions in regard to the establishment of regenerated larch seedlings and symbiotic microorganisms
