Simulated aboveground herbivory is not a source of context dependence in plant-soil feedbacks for individually-grown native and invasive woodland plants

Purpose Plant-soil feedbacks (PSF) and aboveground herbivory are ubiquitous processes that drive plant community structure and affect plant invasion success. There are multiple pathways through which PSF and herbivory may interact, yet few studies have explored PSF-herbivory interactions. We addressed this knowledge gap with a full reciprocal PSF greenhouse experiment involving three native and three invasive plant species of eastern U.S. deciduous woodland. Methods In phase I, each species was planted individually in woodland soil and assigned to two herbivory treatments: unclipped controls and aboveground herbivory simulated by clipping. In phase II, each species was grown individually in all Phase I conditioned soil types. Individual and net pairwise feedbacks are presented separately for aboveground and belowground biomass measurements. Based on PSF and invasion theory, we expected that feedbacks among native species would generally be negative, feedbacks among native and invasive species would tend to favor invasive species, and aboveground herbivory would weaken feedbacks. Results In contrast with predictions, most PSFs were neutral and herbivory did not affect PSFs. Significant negative net pairwise PSF was only detected for belowground biomass, was significantly negative for one native-native pair, and did not favor the invasive species in the two cases of significant PSF found for native-invasive species pairs. Significant negative net pairwise PSF was found for one invasive-invasive species pair. Conclusions Our results suggest that PSF is not a strong dynamic amongst our study species with or without simulated herbivory, at least not for individually grown plants.