Fig. 3

Influence of neighbourhood competition on dependent variables: DBH, height, HD ratio and branch-free bole length of target oaks grown in (a) one 10-year-old group planting stand (Altenheim) and (b) two 20-year-old group planting stands. Impacts of aggregate competition and competition from different plant groups were separately calculated from the Eqs. 1 and 2, respectively (see ‘Materials and methods’ section and description in Fig. 2). In Altenheim stand, no competitors were found from pioneer tree species. Thin bars represent a standard error of parameter estimates and should not touch the zero line for a significant effect