Plant Responses to Temperature Along Japan's Latitudinal Gradient: A Reciprocal Transplant Experiment
 
 
Understanding how tree growth and distributions respond to temperature is critical for predicting future forest range shifts under global warming. However, realized distributions do not necessarily reflect species’ potential thermal niches, because they are shaped by dispersal limitation and biotic interactions in addition to temperature. Reciprocal transplant experiments offer a robust way to isolate thermal effects and verify the potential thermal growth responses.
 
In this study, we implemented a latitudinal reciprocal transplant experiment across four sites in Japan (Tomakomai City, Nikko City, Kyoto City, Yakushima Island), spanning a broad climatic gradient (mean annual temperature 7.9 ~ 21 °C). Uniform nursery-grown seedlings of eight species were reciprocally planted under standardized soil conditions and consistent management. The species set included two boreal conifers, two cold-temperate deciduous broadleaf trees, two warm-temperate deciduous broadleaf trees, and two warm-temperate evergreen broadleaf trees.
 
We quantified seasonal growth (height and diameter increments) and phenology from March 2024 to Dec 2025. We found that (1) all species grew better at warmer sites, rather than performing best at their home site in the first growing season; (2) at the cold sites, warm‐adapted species suffered severe winter damage, resulting in poor over-winter performance (e.g. shoot/branch and leaf mortality); (3) at the warm sites, warm-adapted species outperformed cold-adapted species because they benefited more from longer growth period; and (4) among the studied species, growth performance was trade-off against cold tolerance.
 
These findings reveal growth potential during the growing season alone do not determine species distribution across temperature gradients. Instead, a combination of growth potential, cold tolerance and their trade-off may determine where a species can thrive. The integrated perspective is essential for predicting how woody species will respond to climate change.