Native and Non-native Grasses Generate Common Types of Plant–soil Feedbacks by Altering Soil Nutrients and Microbial Communities

Soil conditioning occurs when plants alter features of their soil environment. When these alterations affect subsequent plant growth, it is a plant–soil feedback. Plant–soil feedbacks are an important and understudied aspect of aboveground– belowground linkages in plant ecology that influence plant coexistence, invasion and restoration. Here, we examine plant–soil feedback dynamics of seven co-occurring native and non-native grass species to address the questions of how plants modify their soil environment, do those modifications inhibit or favor their own species relative to other species, and do non-natives exhibit different plant–soil feedback dynamics than natives. We used a two-phase design, wherein a first generation of plants was grown to induce species-specific changes in the soil and a second generation of plants was used as a bioassay to determine the effects of those changes. We also used path-analysis to examine the potential chain of effects of the first generation on soil nutrients and soil microbial composition and on bioassay plant performance. Our findings show species-specific (rather than consistent within groups of natives and non-natives) soil conditioning effects on both soil nutrients and the soil microbial community by plants. Additionally, native species produced plant–soil feedback types that benefit other species more than themselves and non-native invasive species tended to produce plant– soil feedback types that benefit themselves more than other species. These results, coupled with previous field observations, support hypotheses that plant–soil feedbacks may be a mechanism by which some non-native species increase their invasive potential and plant–soil feedbacks may influence the vulnerability of a site to invasion