Growth and chemical composition of silver birch:Comparative study between Lithuania and Romania

The effects of different climatic conditions on growth and chemical composition of Betula pendula in geographically different European regions,Lithuania and Romania,were compared.Birch species in the entire area have a wide natural distribution,but B.pendula is commercially more important in Lithuania than in Romania.Here we evaluated tree ring width,wood density and foliar chemical composition of mature birch trees in two European regions.Trees at the Lithuanian sites had greater radial growth and wood density with no clear changes in foliar chemistry than those at the Romanian sites.Mean wood density was 600-700 kg m^(-3) at Lithuanian and 350-450 kg m^(-3) at Romanian sites.Mean width of wood ring,earlywood and latewood for Lithuanian birch trees were several times higher than the means for Romanian birch trees.We hypothesized that the main differences in birch radial growth and wood density were due to the different climatic conditions in the studied regions.Ca,K and Mg concentrations were significantly higher and Fe and Mn were lower in the birch foliage at the Lithuanian sites compared those at the Romanian sites.Overall assessment of growth showed that silver birch cultivation is more appropriate for colder climate regions and that birch growth may change in the context of a warming climate.