Conclusion
Literature on PSFs is in need for more mechanistic approaches to unravel the biological drivers of the observed plant growth responses to soil biota. In this study, we provide compelling evidence contradicting the common assumption that negative plant growth response to soil biota is driven by pathogenic microorganisms. We also show that positive plant growth responses are very rarely driven by well-known nutritional or biocontrol microorganisms such as plant growth promoting bacteria or mycorrhizal fungi. Rather, our results point to chemoautotrophs (N-cyclers) and saprotrophs as the main drivers of plant growth response in our system. This, as a whole, constitutes a plea to bring back nutrient cycling as a central component for the development of PSF (e.g., in’t Zandt et al. , in press ), in a literature that has become dominated by trophic, top-down interactions (i.e., pathogens and nutritional symbionts).