Forest ageing : an unexpected driver of beech leaf litter quality variability in European forests with strong consequences on soil processes

The role of forest age as a potential driver of intraspecific variation in leaf litter quality, that is a key plant trait determining ecosystem functioning, has largely been neglected. Using a set of fully replicated pure beech (Fagus sylvatica) forest stands differing in age (15, 65, 95 and 130 years), we quantified the forest stand age related variability of twelve leaf litter quality traits. Litter Mg, N and K showed significantly higher concentrations in litter from 15-yrs-old stands and decreased with increasing stand age. Mn was the only nutrient analyzed that was highest in the oldest stands. Hemicellulose and cellulose were lowest, and lignin and lignin/N ratio were highest in stands of intermediate age. The amount of N within the litter lignin fraction was highest in the 95-yrs-old stands (51% of total N) and lowest in the oldest stands (34% of total N). The amount of N associated within the hemicellulose fraction (