Facilitation and Antagonism in Mycorrhizal Networks

Abstract

Plants of the same and different species are often linked by common mycorrhizal networks (CMNs), and there is substantial disagreement in the litera- ture about whether these linkages have important effects on plant-plant interactions, beyond simply providing mycorrhizal inoculum. Here, I attempt to reconcile opposing viewpoints by reviewing available evidence for three distinct mechanisms by which CMNs can affect plant-plant interactions. I also analyze the details of manipulative field experiments that have been conducted to test CMN effects on plant-plant interactions, and make recommendations for the kinds of future studies that will be most useful in moving forward. I argue that few experiments have unequivocally tested whether CMNs have unique effects on plant-plant interactions, and that these experiments have largely been ignored in favor of debates about the magnitude of resource flows (especially carbon) from plant to plant through CMNs. I suggest that progress on the debate will only be made through more thorough testing of alternative mechanisms besides plant-to-plant carbon flow, especially coupled with experimental manipulations of CMNs to test for consequences on specific aspects of plant community ecological processes. Keywords