Leaf litter decomposition in mixture depends on its own abundance and neighbor richness in an alpine meadow

Abstract

Background and aims

Litter decomposition shapes nutrients dynamics and ecosystem functioning. Effects of component leaf litter abundance and species richness in a mixture on its own decomposition remain unclear.

Methods

Using leaf litter of 1 to 5 coexisting species, we manipulated the proportions of mixed litters (resulting in 106 different mixtures), and monitored the biomass decomposition of individual species component in mixtures over a year. For each species, we separately recognized two gradients: focal species abundance (i.e., leaf litter abundance) and species richness (i.e., the number of other plant species surrounding the focal species in mixtures) in mixtures. We then simultaneously considered both effects of litter abundance and richness on litter mass loss at species level.

Results

Species abundance could increase its own litter decomposition (i.e., abundance effects) at least for Thermopsis lanceolata and Anemone rivularis, and species richness promoted litter decomposition of the reference species (i.e., richness effects) for each species. High quality of leaf litter (low cellulose:nitrogen, etc.) at species level promoted abundance effects, while low quality (high hemicellulose:phosphorus, etc.) enhanced richness effects.

Conclusion

There were positive effects of component litter abundance and species richness in the mixture on its own decomposition, and the effects of both depended on its own initial litter quality. These results set a new path to improving our understanding of litter decomposition in natural ecosystems. This study suggests that in the future, theoretical models and experimental studies of litter decomposition need to consider the influence of abundance of litter components in the mixture.