Nutrient fluctuations alter effects of litter diversity of invasive species on native communities

Invasive alien plants can indirectly suppress native plants by altering soil biota and nutrient cycling through their litter input. The diversity of litter resulting from co-invasion by multiple species may further modulate these impacts. Fluctuating resources are known to favour many invasive plants; however, it is unclear how nutrient fluctuations alter the effects of litter diversity of invasive plants on native communities. Therefore, we grew a native plant community in a control soil without litter, as well as in soils mixed with litter from one, two, three, and six invasive species under constant or pulsed nutrient supply. Invasive species litter altered soil microbial communities, and increased soil total nitrogen concentration and native community biomass. Under pulsed nutrient supply, native community biomass and soil total phosphorus concentration decreased with increasing litter diversity of the invasive species. However, these effects did not occur under constant nutrient supply. A structural equation model indicated that soil phosphorus and fungal community composition were key mediating factors driving the decrease in native community biomass with increasing litter diversity under pulsed nutrient supply. Our findings underscore that the impact of alien invaders on native communities depends on the diversity of the alien plant litter and nutrient fluctuations.