Peeking into the black box: A trait-based approach to predicting plant-soil feedback

Feedbacks between plants and soil communities may be elusive, yet they have far-reaching consequences for plant physiology, competition and community structure. Plant–soil feedbacks (PSFs) are plant-mediated changes to soil properties that ultimately influence the performance of the same or other plants (Van der Putten et al., 2013). These PSFs may be mediated by root-associated organisms (hereafter, root-mediated feedbacks) or saprotrophic organisms and associated litter characteristics (hereafter, litter-mediated feedbacks). However, we know little about the potential mechanistic linkages and relative strengths between these distinct, but connected, processes as root- and litter-mediated feedbacks have generally been studied independently from each other. This is despite the fact that root-associated organisms and saprotrophs can interact through various mechanisms, either directly or as mediated by the plant (e.g. Wardle, 2006). By using a trait-based approach,Ke et al. (in this issue of New Phytologist, pp. 329–341) make an important contribution by integrating root- and litter-mediated PSFs in a nitrogen (N)-based, stage-structured plant population and microbial community model. Their approach allows us to start peeking into the ‘black box’ thereby promoting a better understanding of how PSFs operate interactively. Ke et al. considered various plant traits (e.g. decomposability), but also incorporated trait variation in the physiology, demography and composition of the soil microbial community, and tested their separate and interactive effects on PSF strength in a comprehensive simulation framework. Finally, they used empirical evidence from the literature to support their model predictions