Fire effects on soil biota alter the strength and direction of plant-soil feedbacks

Abstract

Abstract Background and aims Plant soil feedbacks (PSF) are reciprocal mechanisms through which plants modify 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. Methods In this work we evaluated how fire effects on Schizachyrium scoparium and Rudbeckia hirta trained soil biota influenced feedbacks on plant growth. We tested this by experimentally manipulating fires and evaluating plant growth responses to burned and unburned inter- and intraspecific soil biota treatments. 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 potentially modify plant growth, 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 contribute to plant community assembly and fire-fuel dynamics in fire recurrent grassland and savanna ecosystems. Further, this study shows that fire effects on PSFs vary between plant species, and may contribute to the dominance of C4 grasses in pyrophilic ecosystems.