Non-negligible contribution of subordinates in community-level litter decomposition: deciduous trees in an evergreen world
1. Subordinates have relatively low abundance compared to dominants, but they may contribute substantially to functional diversity and ecosystem functions, especially if they differ strongly from the dominants in key traits. Here we investigated whether this phenomenon can be applied to litter decomposition as a key carbon and nutrient cycling process. 2. We hypothesized that species' litter mass-weighted predictions of community-level litter decomposition based on the rates of dominants only would deviate strongly from observed community-level rates and that predictions would improve as subordinates with strongly contrasting traits were combined with those of the dominants. 3. We tested this hypothesis through a one-year field decomposition experiment across a chronological sequence in subtropical evergreen broad-leaved forest. The experiment included single-species litter of evergreen dominants, evergreen subordinates, deciduous subordinates, respectively, as well as community-level litter mixtures. 4. The expected community weighted mean decomposition rates based on the evergreen dominants alone, with or without the addition of evergreen subordinates, deviated strongly from those of observed community litter mixture at the middle and late succession stages but not at the early stage. When adding the deciduous subordinates to the expectation, there was no longer any difference to observed community litter decomposition rate across succession stages. Deciduous subordinates alone explained 7%, 21% and 15% of the total variation in community litter mixture decomposition rate for early, middle and late successional stage, respectively, i.e., more than would be expected from their litter mass fraction. 5. Synthesis. Deciduous subordinates with strongly contrasting nutritional and water-storing traits compared to the dominant evergreens significantly impact litter decomposition at the community-level in spite of their low abundance. This study highlights the importance of "being different" for subordinates to be influential in ecosystem carbon cycling.
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- 10.1111/1365-2745.13341 (DOI)