The role of competition in moderating plant–soil feedback for restoring ecosystems invaded by Brazilian peppertree ( <i>Schinus terebinthifolia</i> Raddi)

Abstract Introduction Ecosystem restoration requires the management of invasive plants due to the harmful effects they have on both above‐ and belowground ecosystem processes. Belowground soil modifications by invasive plants, particularly those driven by plant–soil feedbacks (PSFs), are thought to significantly influence an invader's success by creating soil conditions that affect native and invasive plant performance. Brazilian peppertree ( Schinus terebinthifolia ) is an invasive tree suspected to negatively influence plant communities through PSFs. Objectives This study examined the impact of S. terebinthifolia and its associated soil microbial community on the efficacy of restoration efforts. Methods We conducted a controlled greenhouse competition experiment between the invader and native south Texas grasses, using soil inoculum from invaded and uninvaded sites. Results Schinus terebinthifolia ‐invaded soils consistently exerted a negative PSF on native grasses, reducing their height by 10% and biomass by 24%. Similarly, S. terebinthifolia ‐invaded soils reduced its own biomass by 15% when grown alone. However, the negative direct PSF was neutralized when in competition with native grasses, resulting in a net‐positive PSF for S. terebinthifolia driven by negative interspecific feedbacks. While many studies report that positive PSFs promote invader success, our results demonstrate that negative feedbacks can also facilitate invasion by disproportionately suppressing natives. Notably, native competition lowered S. terebinthifolia biomass by 52%. This, along with improved native grass performance in uninvaded, competition‐free soils, highlights the importance of revegetation in restoration efforts. Conclusions Restoration planning, implementation, and monitoring should account for species‐specific PSFs, soil legacies, and native revegetation competition.