Do ectomycorrhizae follow market law? An analysis of functional trait distribution in response to anthropogenic environmental change

Abstract

Ectomycorrhizal fungi (EMF) are considered instrumental mediators of numerous element cycles, including carbon (C). The ectomycorrhizal guild, however, is functionally diverse, rendering C mediation community-specific. Most studies investigating the effects of environmental change on EMF to date have focused on the taxonomic rather than functional response, limiting our understanding of EMF feedbacks to global change. Studies that have included the functional response generally only frame one environmental indicator, like atmospheric nitrogen (N) deposition, excluding other possible environmental drivers of EMF function. I sought to address this gap by examining the distribution of functional traits represented by exploration morphotype across sites in Massachusetts experiencing anthropogenic environmental change with reference to a suite of environmental variables. I tested hypotheses borne of the biological market theory of mycorrhizal ecology and the functional trait framework. My results suggest that EMF responded both taxonomically and functionally to anthropogenic environmental change. Furthermore, trends observed between EMF and environmental variables in this study challenge the biological market theory of mycorrhizal ecology, suggesting that we broaden our framework beyond N dynamics to understand what drives EMF function. Overall, this study highlights the ecological complexity of the ectomycorrhizal guild, prompting us to develop more nuanced and empirically grounded theories in mycorrhizal ecology.