Climate-Growth Response of Cryptomeria japonica Cultivars in Southwestern Japan

Understanding how tree growth responds to climate is important for predicting how plantation forests may react to ongoing climate change. In this study, we exam- ined the climate–growth relationships of six Cryptomeria japonica cultivars across five common-garden sites in southwestern Japan using dendrochronological meth- ods. We analyzed 48 years of ring width data to evaluate how monthly and annual temperature and precipitation affect radial growth at site and cultivar levels. Static and moving correlation analyses revealed that late winter to early spring tempera- tures (February–March) positively influenced radial growth at most sites, likely by facilitating cambial reactivation, while high summer precipitation tended to sup- press growth at some sites, possibly through reduced solar irradiance. Precipitation effects were variable across sites, with autumn rainfall showing positive effects at lower-elevation sites. At the cultivar level, early-growth type cultivars tended to show positive temperature responses, while late-growth types showed more vari- able precipitation responses, though the majority of cultivar-level correlations did not reach statistical significance. Multivariate ordination (PCA) and permutational multivariate analysis of variance (PERMANOVA) on correlation-based response profiles indicated that geographic location was a significant driver of climate-growth response patterns (R2 = 0.28, p = 0.014), while cultivar type explained a substan- tial but non-significant proportion of variance (R2 = 0.23, p = 0.085). These results suggest that local environmental conditions primarily shape climate sensitivity in C. japonica, while genetic provenance provides an additional, non-negligible layer of variation. Our findings underscore the importance of considering both site char - acteristics and cultivar characteristics in forest management and climate adaptation strategies for C. japonica plantations.