A synthesis on the role of mycorrhizal fungal traits for understanding forest tree functions

Abstract

AbstractNearly all tree species associate with mycorrhizal fungi, which promote their hosts in soil resource acquisition and influence the nutrient economy of the ecosystem. Yet despite the fundamentality of this symbiotic interaction, our understanding how fungal traits relate to host traits is still in its infancy. We compiled a unique mycorrhizal fungal trait database, which sets fungal effect traits in relation to host response functions in the tree response trait categories (i) resource acquisition, (ii) plant productivity, and (iii) carbon (C) release. Based on meta-analysis, we demonstrate current strengths and gaps of knowledge with respect to tree species and spatial coverage, and fungal trait-tree function relationships. Most studies demonstrate a positive influence of traits in the effect trait categories ‘fungal community assembly’, ‘host-symbiont interactions’, and ‘soil exploration’ on traits in the response trait categories ‘resource acquisition’ and ‘plant production’. By contrast, traits in the category ‘fungal community assembly’ related negatively to root C exudation (with low certainty). The influence of mycorrhizal colonization or ‘soil exploration’ effect traits on ‘host C release’ response traits remains unclear. We conclude that the fungal effect trait category ‘soil exploration’ and the tree response trait category ‘C release’ remain major avenues for future research, which should advance from lab-measurements of soft traits and increasingly focus on mycorrhizal traits with the widest importance in ecosystem functioning.