<em>Betula ermanii Cham.</em> provenance trial in Japan: Survival, height, diameter, and productivity data

Understanding the response of Betula ermanii Cham. to climate change is crucial for conservation efforts. Provenance trials provide valuable insights into local adaptation and phenotypic plasticity, aiding in the maintenance of performance in boreal and alpine forest ecosystems. This study aimed to evaluate the impact of climate change on the performance of B. ermanii, and to formulate conservation strategies for future climates. Using survival and growth data from provenance trials, a performance model was developed and applied to projected climate scenarios obtained from WorldClim. Results indicated that the performance of all provenances declines under warming. Particularly, the southern-edge Kinki provenance struggled to survive both in situ and *ex situ *under climate warming. These findings emphasize the necessity of integrating both in situ and ex situ conservation measures tailored to seed source provenances. Provenance trial data provide valuable insights into how climatic responses affect provenances, guiding conservation efforts for B. ermanii in the face of changing environmental conditions. Methods Betula ermanii Cham., a wind-pollinated deciduous tree species, is a significant component of Japan's deciduous broad-leaved forests, particularly prevalent in subalpine regions and forest margins, where it often forms pure forests. Seeds of B. ermanii were gathered during the autumns of 2016 and 2017 from 11 provenances across its distribution zones. These seeds were grown in the nursery at the University of Tokyo Hokkaido Forest (UTHF) in April 2018. Following two growing seasons, containerized saplings were planted at 11 planting sites across Japan in autumn 2019 and spring 2020. Each planting site received 20 seedlings per population, with exceptions for Akkeshi (AKSs), Goyo-San (GYSs), and Choukai-San (CKSs). This endeavor resulted in a total of 2013 seedlings (183 seedlings × 11 planting sites). Random planting designs were implemented for each site to mitigate spatial autocorrelation issues. Survival counts, height, and diameter measurements were conducted in autumn from 2020 to 2023. The performance (productivity index) was calculated by multiplying the survival rate by the average height of each site. Relative differences in climatic parameters between the planting site and the seed source population were analyzed. To forecast future climate, data were obtained from the WorldClim database (Hijmans et al., 2005). The differences in climate variables between the provenance trials and provenances from 2011 to 2022 were calculated.