Invasive plants differentially affect soil biota through litter and rhizosphere pathways: a meta-analysis

Invasive plants affect soil biota through litter and rhizosphere inputs, but the direction and magnitude of these effects are variable. We conducted a meta-analysis to examine the different effects of litter and rhizosphere of invasive plants on soil communities and nutrient cycling. Our results showed that invasive plants increased bacterial biomass by 16%, detritivore abundance by 119% and microbivore abundance by 89% through litter pathway. In the rhizosphere, invasive plants reduced bacterial biomass by 12%, herbivore abundance by 55% and predator abundance by 52%, but increased AM fungal biomass by 36%. Moreover, CO2 efflux, N mineralisation rate and enzyme activities were all higher in invasive than native rhizosphere soils. These findings indicate that invasive plants may support more decomposers that in turn stimulate nutrient release via litter effect, and enhance nutrient uptake by reducing root grazing but forming more symbioses in the rhizosphere. Thus, we hypothesise that litter- and root-based loops are probably linked to generate positive feedback of invaders on soil systems through stimulating nutrient cycling, consequently facilitating plant invasion. Our findings from limited cases with diverse contexts suggest that more studies are needed to differentiate litter and rhizosphere effects within single systems to better understand invasive plant-soil interactions.