Negative plant-soil feedback and species coexistence

Different mechanisms, including equilibrium and non-equilibrium processes, have been taken into account as possible theoretical explanations of species coexistence. Despite the ample evidence on the existence of negative plant-soil feedback in both agriculture and natural vegetation, the role of these processes in the organization and dynamics of plant communities has so far been neglected. In this study, simulations by an individual-based competition model show how the intensity of negative feedback on individual plant performance can produce faster successional dynamics and allow species coexistence in two- and multi-species systems. The results show that even low levels of negative plant-soil feedback can enable species coexistence and often produce cyclic population dynamics. Moreover, the model highlights how negative feedback can generate positive reciprocal interspecific interactions at the population level, despite the fact that only competitive interactions is present between individual plants. In fact, competitive effects occur on a short-term scale, but positive reciprocal species interactions emerge only if negative feedback affects all species and if longer periods of simulation, more than the species life span, are considered. An important outcome of the model is the evidence that the effects at population level are timescale-dependent, thus showing the limitation of short-term species removal experiments used in traditional competition studies.