Leaf litter decomposition is closely linked to nutrient cycling and driven by environmental conditions, species-specific leaf chemistry, and here in particular by polyphenols composition. However, not much attention has been paid on the decomposition of polyphenols themselves. We hypothesized that phenolics and tannin decomposition rates are species-specific and positively affected by litter species richness. Leaf litter of three Chinese tree species was exposed to field decomposition conditions, aggregated in mixtures of different species richness (1-, 2-, 3-species mixtures). We sampled litter five times over the course of 171 days, calculated species-specific total phenolics and total protein precipitable tannin decomposition rates, assessed changes in polyphenol composition using HPLC, and tentatively identified compounds by LC-ESI-MS/MS. Leaf litter richness effects on phenolics and tannin decomposition rates were positive, except for Sapindus-specific tannins, and differed between leaf litter species. Decomposition duration changed polyphenol compositions, and significantly interacted with leaf litter species richness with increasing effects of litter richness with time. Litter diversity effects on polyphenol decomposition are crucial for whole leaf litter decomposition. The contrasting dependencies of phenolics and tannin decomposition rates on leaf litter richness may provide explanations for equivocal results in leaf litter mixture experiments.

See Materials and Methods in the corresponding manuscript.

The NILEx Site is situated near Site A (Experimental site in Xingangshan) small near-natural forest remnant on the east-northeastern end of the experimental plot.

Quercus acutissima, Sapindus saponaria, Schima superba

Phenolics and Tannin contents (colums Phenolics; Tannin) were determined using a) the photospectrometric methods based on the prussian blue method; b) using the radial difusion assay for increased sensitivity (both described in Hagerman, 2002 The Tannin Handbook as well as in Eichenberg et al. 2014: Plant polyphenols–implications of different sampling, storage and sample processing in biodiversity-ecosystem functioning experiments; Chemistry & Ecology). All columns entitled peakXY refer to areas of characteristic peaks from the HPLC analysis of the respective samples. For further details see Materials and Methods in the corresponding manuscript.