Beyond nutrients: a meta‐analysis of the diverse effects of arbuscular mycorrhizal fungi on plants and soils

Abstract

Arbuscular mycorrhizal fungi (AMF) can increase plant fitness under certain environmental conditions. Among the mechanisms that may drive this mutualism, the most studied is provisioning of nutrients by AMF in exchange for carbon from plant hosts. However, AMF may also provide a suite of non-nutritional benefits to plants including improved water uptake, disease resistance, plant chemical defense, soil aggregation, and allelochemical transport and protection. Here, we use a meta-analysis of 93 studies to assess the relative effect of AMF on nutritional and non-nutritional factors that may influence plant fitness. We find that the positive effects of AMF on soil aggregation, water flow and disease resistance are equal to the effect of AMF on plant nitrogen and phosphorus uptake. However, AMF had no effect on the uptake of other nutrients, plant water content, allelopathic transport or production of chemical defense compounds. We suggest future research directions, including experimentally assessing the relative contribution on plant fitness of AMF interactions by untangling the independence of alternative benefits of AMF from an increase in nutrient uptake. This will lead to a more holistic view of the mycorrhizal-plant association and a more accurate picture of the net impact on the plant or plant community in question.

In situ mycorrhizal function – knowledge gaps and future directions

“…This is particularly interesting given the recent Delavaux et al . () meta‐analysis showing that services other than nutrient acquisition can be equally important in AM, and results by Bennett et al . () highlighting the central role of pathogen protection by EM fungi.…”

Plant community responses to stand‐level nutrient fertilization in a secondary tropical dry forest

“…However, arbuscular mycorrhizae can enhance plant water status (Delavaux et al. ); therefore, it is possible that trees maintained investment in their fungal symbionts to promote water rather than nutrient uptake. If our results can be generalized to other tropical dry forests (which we admit is speculative), this would imply a fundamental difference between how wet forests vs. seasonally dry, water‐limited forests respond to nutrient addition.…”

The role of plant–soil feedbacks in stabilizing a reindeer‐induced vegetation shift in subarctic tundra

“…However, the role of mycorrhizas has increasingly been shown to vary from mutualistic to parasitic, depending on the abiotic and biotic context (Johnson & Graham, ; Varga, Vega‐Frutis, & Kytöviita, ). Moreover, the beneficial effect of mycorrhiza is not always correlated with level of root colonization (Treseder, ), and mycorrhiza also influence plants in ways unrelated to the nutrient uptake, for example influencing water uptake or disease resistance (Delavaux et al., ). This means either that the mycorrhizal colonization we observed had a negative effect on B. nana growth, or that the positive effect of mycorrhizas is obscured by other biotic interactions.…”