Species origin and ecological context shape heterogeneous climate sensitivity of temperate conifer growth

Temperate conifer forests underpin European ecosystems and economies, making it essential to understand how they respond to climate change. Yet most empirical studies estimate average climate responses that mask variability across biological and ecological scales. Using a cross-classified multilevel model, we estimate heterogeneous climate sensitivities across trees, species, and ecological regions while accounting for temporal dynamics, competition, stand characteristics, and within- and between-group size variation. Spring temperature emerges as the dominant seasonal driver of radial growth, but its effect varies markedly across species and ecological regions. Conditional on the covariates included in the model, trees in native contexts exhibit lower average growth than trees in introduced contexts while responding more strongly to warmer spring conditions. Controlling for tree size attenuates the estimated temperature effect, showing that part of the apparent climate response reflects ontogenetic structure rather than intrinsic physiological sensitivity. Consequently, climate sensitivity cannot be inferred from species identity alone but reflects both species-level differences and ecological context. Models imposing homogeneous climate responses therefore risk misrepresenting heterogeneity in forest climate sensitivity. If these differential inter-annual climate sensitivities persist under longer-term warming, they could contribute to changes in the relative performance and composition of temperate conifer forests.