Background and aims

Plant invasion is a major component of global environmental change and can significantly alter soil biota, and soil biological activities through rhizosphere inputs, which are essential for organic matter decomposition and nutrient cycling in terrestrial ecosystems. However, the relationship between plant invasion, invasive plant’s growth form, allelopathy, soil biota and soil enzymatic activity remains unclear. The aim of the study was to evaluate the impact of plant invasion, plant and ecosystem type on soil biota, soil biological activity and nutrients.

Methods

We conducted a comprehensive meta-analysis from 107 studies and extracted 688 paired observations. We examined the responses of soil biota functional groups, enzymatic activity, microbial biomass, soil respiration, N-mineralization, N-nitrification, and soil nutrient levels (available nitrogen, and available phosphorus) to plant invasion, allelopathy of invasive plants, growth forms, and ecosystem types. The effect sizes of invasive plants on the response variables were calculated using log response ratio. The ratio was computed using the mean values obtained from a pair of response variables in the invasive and native plants. Moreover, a fail-safe number calculated to detect the biasness of the studies.

Results

Plant invasion affected soil biota functional groups, the abundance of some soil enzymes, microbial biomass and soil nutrients. Our results showed that invasive plants reduced the abundance of herbivores by 45%, detritivores by 27% and omnivores by 45%, but increased arbuscular mycorrhizal fungal (AMF) biomass by 29%, microbial biomass carbon (MBC) by 19% and microbial biomass nitrogen (MBN) by 32%, respectively. Soil microbial biomass, N-mineralization, soil respiration, available (N, P) nutrients, NH4+-N and nutrient stocks were all higher in invasive than native plants rhizosphere soils. Furthermore, the effects of invasive plants on soil enzyme activities were inconsistent, showing higher C-decomposing (invertase, phenol oxidase and β-glucosidase) and N- and P-releasing enzyme activities ($+$ 18% to $+$ 27%) under invasive plant soils compared to native plant soils. 

Conclusion

Results showed that a decrease in certain soil functional groups, and an increase in symbiont abundance under invasive plants soils compared to native plants soils. However, invasive plants enhanced soil nutrient-releasing enzymes and available nutrients, thereby accelerating nutrient cycling and promoting their persistence and success.