Review on fire effects on ectomycorrhizal symbiosis, an unachieved work for a scalding topic

Abstract

Millions of hectares of ectomycorrhizal (ECM) forests provide most of the wood resource in the northern hemisphere. Among these forests, those that are fire-prone concentrate an astonishing diversity of mutualistic soil fungi that are pivotal for seedling establishment, tree growth and forest functioning and dynamics. Here, we review the effects of fire on ECM symbiosis in these forests using a systematic screening of the literature. We reveal that a low number of field studies (73) directly address fire effect on ECM symbiosis, in a restricted geographic area that partially represents the geography of ECM biodiversity stakes and fire risk. The analyzed literature consensually reports long-term shifts in the composition of ECM fungal communities after fire. Contrastingly, the effects of fire on fungal diversity and richness at the local scale continue to be debated among researchers, and need to be documented further using adequate experimental device to limit the effects of some identified methodological biases. Furthermore, our analysis emphasizes the urgent need to carefully consider the belowground effects of prescribed burning. This is an important conclusion because this widely implemented and efficient management tool to prevent wildfires may impact ECM soil communities in the same way as uncontrolled events. Our analysis finally highlights the need of refining the concept of post-fire ECM fungi, by taking advantage of promising tools, such as next-generation sequencing and quantitative PCR applied to mycelia and spores, to integrate the vegetative traits of fungi in integrative definitions.