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).