Aboveground-belowground coupling

Rapid transitions in ecosystems can be strongly mediated by plant-soil interactions: On the one hand, plant-soil interactions can increase the resistance of the ecosystem to rapid transitions, if transitions lead to soil biota that limits disproportional abundance of some plant species over others, promoting diversity maintenance (negative plant soil feedbacks). On the other hand, soil biota can exacerbate the effects of rapid transitions, e.g. if transitions lead to soil biota that promotes dominance of few plant species, leading to species losses (positive plant soil feedbacks). Understanding the interaction of above- and belowground compartments of terrestrial ecosystems in response to rapid transitions is thus an important area that requires strong conceptual bridges. To this end, we addressed the following three main hypotheses:

• Plant root traits predict assemblages of root-inhabiting and rhizosphere-associated biota, with feedback processes linking trait compositions of above- and belowground communities; and
• Two abiotic current ecological pressures, drought and microplastic in isolation and in combination impact soil assemblages with shifted average trait values; and
• The hypothesized shifts in above- and belowground communities and their average trait values will further impact the resilience and resistance of the plant-soil system.