The potential for mass ratio and trait divergence effects to explain idiosyncratic impacts of nonnative invasive plants on carbon mineralization of decomposing leaf litter

1. Invasive plant effects on litter decomposition tend to be idiosyncratic among species and ecosystems, which may arise from variation in the invader’s relative abundance (mass ratio effect), its relative functional difference to other species (trait divergence effect), and/or from species’ litter mixing that causes non-additive decomposition rates relative to single-species decomposition. 2. We use experimental microcosms to quantify the potential for mass ratio and trait divergence to explain effects of invasive litters on carbon mineralization rates of decomposing litter mixtures and to generate non-additive dynamics in two distinct forest litter types. 3. The relative strength and direction of the mass ratio and trait divergence effects on carbon mineralization values were moderated by interactions between each effect and the canopy litter mixture. In both maple-poplar and oak hickory litter mixtures, we found that the strength of the trait divergence effect increased with increasi...