Soil macrofauna and leaf functional traits drive the decomposition of secondary metabolites in leaf litter

Leaf litter decomposition is closely linked to soil nutrient cycling. Both vary with environmental conditions, leaf litter diversity, faunal decomposer community and leaf litter chemistry. Polyphenols, i.e. phenolics and tannins, are important secondary metabolites in leaf litter and are considered a major impediment to whole-leaf decomposition. While the function of polyphenols is well studied, the mechanisms and drivers of their decomposition are largely unknown. We reasoned that polyphenol decomposition is driven by the same factors as whole-leaf decomposition. We hypothesized that polyphenol decomposition rates increase with leaf litter richness, decrease with macrofauna exclusion and are related to traits characterizing leaf litter quality.