Variation in 13 leaf morphological and physiological traits within a silver birch (Betula pendula) stand and their relation to growth

Differences between genotypes are important for the ability of local populations to cope with environmental stress, especially in sessile, long-lived organisms such as trees. Despite the importance, differences between genotypes within local populations in traits relevant for growth are still unexplored. In this study, we examined differences between genotypes, studying 13 physiological and morphological traits and their relation to growth, using 15 silver birch (Betula pendula Roth) genotypes representing a natural population. Our data show the complex regulation of growth under field conditions. There were differences between genotypes in all measured traits, but the genotypes occupied a continuous, narrow range of values for individual traits. Although leaf morphological traits had most explanatory power for the variation in estimated biomass, the differences between genotypes in individual traits seemed random. Exceptions were specific leaf area (SLA) and the fresh mass to dry mass ratio of the leaves (FMDM), which correlated well with estimated biomass. Additionally, genotypes with high biomass tended to have more stable SLA and FMDM values across years. Thus, within a local silver birch population, different morphological and physiological configurations can lead to a similar outcome in terms of biomass, but SLA and FMDM are important for good growth under field conditions.