To elucidate the physiological and morphological factors underlying intraspecific variation in growth rate, we examined the variation in leaf and whole-tree traits for three geographical variations of ca. 45-year-old Japanese cedar (Cryptomeria japonica D. Don) with contrasting heights and radial growth in a common garden. Traits that reflect leaf-level photosynthesis, water relations, and whole-tree level crown structure in relation to light use and hydraulic architecture were measured. Overall, intraspecific variation in growth characteristics in field-grown adult trees was regulated by whole-tree properties rather than leaf properties. Most leaf traits were similar among provenances. Nevertheless, the leaf traits exhibited highest maximum net photosynthetic rate, dark respiration rate, and light compensation point in provenances whose native habitats are most similar to the common garden in the present study. Together with previous reports that this provenance has higher root nutrient acquisition capacity than the other two provenances, it can be said that organ-level resource use strategies are coupled in a tandem manner. At the whole-tree level, hydraulic architecture-as explained by axial variation in the hydraulically weighted tracheid diameter-can be linked to leaf distribution with respect to light use strategies as well as water transport capacity, leading to differences in growth characteristics among provenances. The study of intraspecific variation in growth characteristics in trees with a wide range of native habitats is expected to be a useful indicator for predicting changes in growth potential and forest dynamics in response to climate change in each habitat.

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Aims Fine root morphological traits regulate the belowground resource acquisition strategies of trees. However, genotypic variations isolated from environmental variations within tree species remain unclear. Thus, this study aimed to clarify the effects of genotypic variations on the fine root morphology of three types of Japanese cedar (Cryptomeria japonica), which were derived from different provenances but were grown in a common garden.Methods In the three geographically different provenances of C. japonica stands (Yanase, Yoshino, and Yaku), fine root morphological traits, such as root length and diameter and specific root length (SRL), were measured for each root up to the 4th branching order.Results Yaku cedar exhibited root traits distinct from the other provenances, such as growing longer and thinner roots in 1st root order to enhance root surface area. In addition, the SRL patterns with root orders and higher root tissue density suggested a resource conservation strategy corresponding to the low aboveground production of Yaku cedar. Yanase cedar demonstrated a significantly higher root branching ratio and specific root tips than the other provenances, indicating a strategy for investing resources in absorptive roots. Although Yoshino cedar had traits similar to that of Yanase cedar or intermediate between Yanase and Yaku cedars, high aboveground production may be achieved by nutrient acquisition with root exudates instead of absorptive root growth.Conclusion Genotypic variations appeared in fine root morphological traits of C. japonica trees, even when grown in the same environments, implying distinct resource acquisition strategies characterized by each provenance.

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