Changes in species evenness of litter have no effect on decomposition processes

Most studies on the importance of litter diversity to decomposition processes have examined effects of species richness, and have not considered the other important aspect of biodiversity, namely evenness (relative abundance of species). Using microcosms, we investigated how changes in species evenness and identity of litters (taken from a regenerating Betula pendula forest) affected decomposition processes. We showed that single litter species varied in their rate of decomposition (bilberry 44.4%, willow 49.9%, rowan 53.7% and birch 54.8% weight loss after 234 days). However, when in mixtures, changes in the evenness of these litters and the identity of the dominant species had no detectable effect on measures of decomposition such as weight loss (42.6-56.6% after 234 days), microbial respiration and dissolved organic carbon and inorganic nitrogen release. Dissolved organic nitrogen release was found to be significantly greater from high evenness litter mixtures, 0.236 mg l(-1), than the single species treatments, 0.145 mg l(-1), but only during the initial stages of the experiment. These results, therefore, provide no support for the idea that changes in evenness of litter inputs and the identity of dominant litters will affect decomposition processes and soil nutrient availability. (C) 2002 Elsevier Science Ltd. All rights reserved.