Trait syndromes underlying stand-level differences in growth and acclimation in 10 silver birch (Betula pendula Roth) genotypes

• Within a local population differences among genotypes occur as a rule.
• Complex trait syndromes differentiated individual genotypes.
• High net assimilation rate and low leaf mass fraction resulted in good growth.
• Genotypes responded in a similar way to adverse environmental conditions.

Differences in the response to adverse environmental conditions among genotypes within local populations are important in determining the ability of local populations to cope with such conditions, especially for long-lived organisms like trees. Nevertheless, such differences and their relevance for acclimation have not been addressed to date, representing a gap in our understanding of tree growth and acclimation. Focussing on temperature and soil moisture we address this issue, evaluating 13 relevant physiological (i.e. gas exchange, leaf pigments) and leaf morphological traits (e.g. specific leaf area) and three traits related to growth partitioning for two growing seasons in 10 genotypes of the ecologically and economically important tree species silver birch (Betula pendula Roth). Complex trait syndromes – a consistent association of plant traits characterising differences among genotypes – including physiological, leaf morphological and growth partitioning traits were identified. The relative investment in leaf mass, shoot-to-root ratio and net assimilation rate were most important for good growth. With regard to acclimation to adverse environmental conditions genotypes mostly acclimated in a similar way, but changes in allocation patterns may depend on genotype, even within a local population. Trees with a high net assimilation rate and a low leaf mass fraction and shoot-to-root ratio produced most biomass after two years of growth. Information on these traits could, in addition to growth, be useful in identifying material for forest regeneration that is robust with regards to expected climate change.