Cambial growth is a phenotypic trait influenced by various physiological processes, numerous biotic and abiotic drivers, as well as by the genetic background. By archiving the outcome of such complex interplay, tree-rings are an exceptional resource for addressing individual long-term growth responses to changing environments and climate. Disentangling the effects of the different drivers of tree growth, however, remains challenging because of the lack of multidisciplinary data. Here, we combine individual dendrochronological, genetic and spatial data to assess the relative importance of genetic similarity and spatial proximity on Norway spruce (Picea abies (L.) Karst.) growth performances. We intensively sampled five plots from two populations in southern and central Europe, characterizing a total of 482 trees. A two-step analytical framework was developed. First, the effects of climate and tree age on tree-ring width (TRW) were estimated for each individual using a random slope linear mixed-effects model. Individual parameters were then tested against genetic and spatial variables by Mantel tests, partial redundancy analyses and variance partitioning. Our modelling approach successfully captured a large fraction of variance in TRW (conditional R2 values up to 0.94) which was largely embedded in inter-individual differences. All statistical approaches consistently showed that genetic similarity was not related to variation in the individual parameters describing growth responses. In contrast, up to 29% of the variance of individual parameters was accounted by spatial variables, revealing that microenvironmental features are more relevant than genetic similarity in determining similar growth patterns. Our study highlights both the advantages of modelling dendrochronological data at the individual level and the relevance of microenvironmental variation on individual growth patterns. These two aspects should be carefully considered in future multidisciplinary studies on growth dynamics in natural populations.

Conservation Biology University of Marburg Karl von Frisch Strasse 8 35043 Marburg Germany

Department of Agricultural Food and Environmental Sciences Marche Polytechnic University Via Brecce Bianche 10 60131 Ancona Italy

Department of Chemistry Life Sciences and Environmental Sustainability University of Parma Parco Area delle Scienze 11 A 43124 Parma Italy

Department of Ecology University of Marburg Karl von Frisch Strasse 8 35043 Marburg Germany

Department of Geography University of Cambridge Downing Place CB2 3EN Cambridge United Kingdom

Department of Geography University of Cambridge Downing Place CB2 3EN Cambridge United Kingdom; Swiss Federal Research Institute WSL Zürcherstrasse 111 8903 Birmensdorf Switzerland; Czech Globe Global Change Research Institute CAS and Masaryk University Kotlárská 2 61137 Brno Czech Republic

National Research Council Institute of Biosciences and Bioresources Via Madonna del Piano 10 50019 Sesto Fiorentino Italy

References provided by Crossref.org

Individual reproductive success in Norway spruce natural populations depends on growth rate, age and sensitivity to temperature

Functional Relationships of Wood Anatomical Traits in Norway Spruce