Towards understanding the impact of mycorrhizal fungal environments on the functioning of terrestrial ecosystems

Abstract

Mutualistic interactions between plants and soil fungi, mycorrhizas, control carbon and nutrient fluxes in terrestrial ecosystems. Soil of ecosystems featuring a particular type of mycorrhiza exhibit specific properties across multiple dimensions of soil functioning. The knowledge about the impacts of mycorrhizal fungi on soil functioning accumulated so far, indicates that these impacts are of major importance, yet poorly conceptualized. We propose a concept of mycorrhizal fungal environments in soil. Within this concept, we discuss knowledge gaps related to the understanding and quantification of mycorrhizal fungal impacts. We introduce an experimental framework to address these gaps in a quantitative manner, and present the field experiment 'Mycotron', where we established vegetation series featuring three mycorrhizal types; ericoid (ERM), ecto- (ECM), and arbuscular mycorrhiza (AM), to quantitatively assess mycorrhizal fungal impacts on soil functioning. The experimental treatments entail manipulations in dominance levels of vegetation of three mycorrhizal types (AM, ECM, and ERM) in standardized soil conditions. This experiment constitutes a unique testbed to quantitatively evaluate the impacts of distinct mycorrhizal fungal environments on a large variety of ecosystem functions. Our approach aids the quantification of microbiota and plant-microbial interaction impacts on soil biochemical cycles. We propose a mycorrhizal fungal environment concept to describe and quantify the impacts of mycorrhizal fungi on soil processes and introduce the new Mycotron common garden experiment to implement and test this concept.