Fire effects on soil biota alter the strength and direction of plant-soil feedbacks between Schizachyrium scoparium (Michx.) Nash and Rudbeckia hirta L

Abstract Background and aims Plant soil feedbacks (PSF) are reciprocal mechanisms through which interactions between plants and soil biota and affect future plant growth. When scaled up to the community level, PSFs are important determinants of above- and belowground community dynamics that influence long-term successional trajectories. Despite over three decades of ecological PSF research, we have a poor understanding of how common environmental processes like fire influence the strength and direction of PSFs. The aim of this study was to evaluate fire effects on PSFs between two common grassland species: Schizachyrium scoparium and Rudbeckia hirta. Methods In this work we evaluated how fire effects on S. scoparium and R. hirta associated soil biota influenced feedbacks on plant growth using a two phase experiment. We tested this by first growing S. scoparium and R. hirta with the same soil inocula, and then simulating low intensity, grassland fires in a controlled greenhouse pot experiment (soil training). We then evaluated plant growth responses to burned and unburned inter- and intraspecific soil biota treatments (response phase). Results Fire effects on inocula neutralized negative feedbacks in S. scoparium, and caused negative feedbacks in R. hirta. This shows that environmental disturbance like fire can alter the strength and direction of PSFs in ways that modify plant growth and potentially influence plant fuel loads and community dynamics. Conclusion That fire can alter the strength and direction of PSFs on plant growth suggests that fire effects on soil related processes may influence plant community dynamics and fire-fuel dynamics in fire recurrent grassland ecosystems. Further, this study shows that fire effects on PSFs vary between plant species.