Morphological plasticity of European beech (Fagus sylvatica L.) in pure and mixed-species stands

The question how tree species allometry in mixed stands differs from pure stands is approached by analyzing how crown morphology of European beech (Fagus sylvatica L.) behaves in intra- versus interspecific neighborhoods. Based on long-term experimental plots with individual tree records on tree allometry and competition, our results revealed that (i) in pure stands crown allometry of beech is far from constant, but closely related to intraspecific competition, (ii) in mixed stands crown allometry of beech is considerably modified by competition reduction when growing in the vicinity of spruce, oak or pine, and (iii) crown extension due to competition reduction by interspecific neighbors increases with site fertility. Implications for the allometric theory, the stress-gradient hypothesis and a general understanding/conceptual model for mixing reactions are discussed.

► The study analyzes on crown plasticity of European beech in pure and mixed stands.
► Crown allometry of beech is closely related to intraspecific competition.
► In mixed stands crown allometry is considerably modified by competition reduction.
► Mixing effects on crown allometry are site-dependent.
► Crown extension due to competition reduction increases with site fertility.