Background: The ecological effects of phenolic compounds in plant tissues are related to their phenolic signature, i.e. the total content and structure of the phenolic compounds. Although the spatial and temporal variation of the phenolic signature within species is well documented, it remains unclear whether intraspecific variation is due to genetic differences between individuals or to environmental conditions.

Aims: We aimed to disentangle the effects of the genetic background and environmental conditions on intraspecific variation in the phenolic signature of beech (Fagus sylvatica) leaf litter.

Methods: In a silvicultural provenance experiment, beech populations from a wide range of the natural distribution range of the species, including different phylogeographic lineages (site of origin = genetic background), were grown in two geographically distinct common gardens (site of growth = environment). The total content and the protein-precipitation capacity of phenolic leaf litter compounds and their HPLC profile were determined as a measure of the phenolic signature of leaf litter of individual beech trees.

Results: The phenolic content and the protein-precipitating capacity of methanolic litter extracts were significantly correlated. Variation in the content of phenolic compounds was largely related to genetic background and less to environment, while the reverse was true for their protein-precipitating capacity. Individuals grown in the same common garden exhibited more similar phenolic signatures than individuals from the same provenance but grown at different locations.

Conclusions: We conclude that it is environmental conditions rather than the genetic background that determines the phenolic signature of leaf litter of beech individuals. It follows from our results that environmental change may in the future lead to alteration of the phenolic signatures of present beech forest ecosystems, probably with a cascading effect on ecological processes such as decomposition.