Study on limiting factors on height growth of old Cryptomeria japonica trees

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We clarified that Site Index (mean tree height of dominant trees) of old Cryptomeria japonica stand in University Forest in Chiba, The University of Tokyo could be estimated with Wetness Index, effective soil depth and topographical openness of the site. We also clarified that mesophyll CO_2 diffusion resistance was one of major limiting factors for photosynthesis of old trees, mesophyll CO_2 diffusion resistance was negatively correlated to present height growth rates, and midday water potential was significantly more negative in slow growing trees than fast growing trees. Foliar water uptake of attached water on foliar surface and movement of absorbed water to xylem in a current shoot was observed and contribution of leaf wetting to recovery from water stress was suggested.