title: Decomposition of diverse litter mixtures in streams.
abstract: In view of growing interest in understanding how biodiversity affects ecosystem functioning, we investigated effects of riparian plant diversity on litter decomposition in forest streams. Leaf litter from 10 deciduous tree species was collected during natural leaf fall at two locations (Massif Central in France and Carpathians in Romania) and exposed in the field in litter bags. There were 35 species combinations, with species richness ranging 1-10. Nonadditive effects on the decomposition of mixed-species litter were minor, although a small synergistic effect was observed in the Massif Central stream where observed litter mass remaining was significantly lower overall than expected from data on single-species litter. In addition, variability in litter mass remaining decreased with litter diversity at both locations. Mean nitrogen concentration of single- and mixed-species litters (0.68-4.47% of litter ash-free dry mass) accounted for a large part of the variation in litter mass loss across species combinations. For a given species or mixture, litter mass loss was also consistently faster in the Massif Central than in the Carpathians, and the similarity in general stream characteristics, other than temperature, suggests that this effect was largely due to differences in thermal regimes. These results support the notion that decomposition of litter mixtures is primarily driven by litter quality and environmental factors, rather than by species richness per se. However, the observed consistent decrease in variability of decomposition rate with increasing plant species richness indicates that conservation of riparian tree diversity is important even when decomposition rates are not greatly influenced by litter mixing.
authors.affiliation: Laboratoire Dynamique de la Biodiversité, UMR 5172 CNRS-UPS, 29 rue Jeanne Marvig, 31055 Toulouse, France. Antoine.Lecerf@ubc.ca
authors.forename: Antoine
authors.initials: A
authors.lastname: Lecerf
authors.forename: Geta
authors.initials: G
authors.lastname: Risnoveanu
authors.forename: Cristina
authors.initials: C
authors.lastname: Popescu
authors.forename: Mark O
authors.initials: MO
authors.lastname: Gessner
authors.forename: Eric
authors.initials: E
authors.lastname: Chauvet
mesh_terms: D001673:Biodegradation, Environmental; D044822:Biodiversity; D005602:France; D018515:Plant Leaves; D045483:Rivers; D014197:Trees