Leaf litter production and litter nutrient dynamics of invasive Acacia mearnsii and native tree species in riparian forests of the Fynbos biome, South Africa

•Acacia mearnsii conserves P more tightly than N in fynbos riparian forests.•The invasive species show two litterfall peaks and native species only one.•High leaf N concentration in A. mearnsii will likely enhance soil N concentrations.•The N-rich leaf litter and soil can alter aquatic environments.