Wood formation dynamics for different provenances of European beech (Fagus sylvatica L.)

Wood formation dynamics were investigated for six different provenances of European beech (Fagus sylvatica L.) for the vegetation periods 2005 and 2006 at a site near Kiel/DE and for the vegetation period 2006 at a site near Vienna/AT. Two trees per year and provenance (2x DE, AT, RO, ES, CZ) were analysed. Onset course and end of wood formation were determined by inserting a thin steel needle into the outer xylem in 1- or 2-week intervals. This so called pinning induces the formation of wound tissue, which clearly indicates the amount of xylem laid down until the individual pinning date as revealed by light microscopy after the vegetation period. Wood formation in all trees followed an S-curve with a short and slowly starting early stage, a middle stage with distinctly increased wood formation and a slowly decreasing stage at the end of the vegetation period. Because of partly extremely acentric growing stems, wood formation was evaluated as relative increment. At both experimental sites, wood formation lasted nearly four months with a beginning in the second half of May and an end around the middle of September. According to tree curves, provenance-specific characteristics of duration and course were not recorded, although a certain tendency of a slightly delayed wood formation might exist for the three origins with warmer yearly average temperatures. It seems that temperature does not play a dominant role especially for the initiation of wood formation.