The advancing mycelial frontier of ectomycorrhizal fungi

This article is a Commentary on Hagenbo et al. (2021), 230: 1609–1622. ‘There exciting potential for coupling in-growth bag approaches with other techniques to advance our fundamental understanding of EMM dynamics.’ Compared mycorrhizas and sporocarps, which are both relatively conspicuous produced in discrete units, quantifying the standing biomass dynamics significant challenge practice because cryptic nature fine threadlike mycelium growing soil (Anderson & Cairney, 2007; Wallander al., 2013). These methodological challenges have historically forced researchers rely estimations based quantification provide limited assessment distribution abundance ectomycorrhizal fungal (Koide 2005). The development methods has improved ability estimate production turnover situ dramatically (Wallander 2001). Briefly, these involve buried bags constructed from mesh material that allows fungi access substrate contained within, then sequentially harvested assess necromass directly (Li King, 2018) or biomarkers such as ergosterol phospholipid fatty acids (PLFAs; 2001) used calculate rates (Fig. 1b; reviewed by While been important illuminating processes, application few systems regions around globe, mostly Scandinavian boreal forests (Ekblad Consequently, fungi, their response environmental factors, influence terrestrial biogeochemical cycles perspective whole fungus remains rather rudimentary. In this issue New Phytologist, (2021; pp. 1609–1622) expand knowledge base examining Mediterranean experiencing varying levels drought stress. it appreciated water limitation major driver colonization community composition (Gehring 1998), we poor its effects EMM. (2021) address gap applying determine biomass, production, relation vegetation type Spain. authors found slower greater stress, may be result negative direct reduced moisture and/or indirect plant productivity C allocation. also document seasonality differences among dominant hosts, where there was steady across year Quercus ilex stands compared more pronounced Pinus pinaster sylvestris stands, suggesting deeper-rooted Q. communities less sensitive periods limitation. results suggest significantly altered increased limitation, especially those hosts particularly suspectable drought. comes challenges, demonstrate great ‘the mycelial frontier’ using conditions previously unexplored. As any method, however, approach limitations deserve consideration future refinement maximize utility. First, always question about how representative colonizing surrounding soil. Exploration strategies vary taxa (Agerer, known discriminate against many do not produce extensive (e.g. Laccaria, Inocybe, Cenococcum, Hebeloma Tuber spp.) avoid mineral substrates Cortinarius spp.; amplified when compositional changes associated functional traits responses treatments, gradients, host composition. filtering bias could easily assessed comparing taxonomic structure entering ones present characterization metabarcoding approaches. Second, assumption sole colonizers filled inert sand foraging patterns saprotrophic assumed strongly governed sources generally holds true studies guilds 2010), recent challenged (Hagenbo 2018). Going forward will crucial ground truth molecular bags, since cannot differentiated PLFA alone Finally, ecological relevance substrate, acid-washed sand, might needs critical evaluation. Inert make substantially easier absence background relic (i.e. DNA spores), however hyphal at least partly external factors resource concentrations (Dowson 1989). When contain an no resources support growth, maintenance cost growth would very high likely rates. Conversely, lack decomposers decay opposite leading low estimated Understanding addressing method continuing refine them next steps towards broad adoption. There 1b). For instance, individual contribute level ecosystem 1c). possess exploration strategy; melanization; extracellular enzymatic suite) only success but functions 2014). body work dynamic anthropogenic change (Bennett Classen, 2020) alteration consequences if corresponding shifts related (McCormack 2010) following death (Fernandez 2016). Over past decade characterize widespread implementation high-throughput sequencing (Lindahl 2013; Nguyen 2015). regularly applied root communities, commonly understand contribution 2010; Phillips, 2014; 2018; Rosenstock 2019). Furthermore, most use ergosterol, PLFAs) opportunity develop high-resolution spectroscopy Fourier-transfer infrared (FTIR); pyrolysis gas chromatography mass spectrometry (py-GCMS)) track specific chemical fractions through time. valuable trying residence times different contributions particulate mineral-associated organic matter pools. example, rate melanin, recalcitrant fraction necromass, extremely estimating size flux slow pool Of course, possibilities technological synergies further exploration. demonstrate, expanded reveal relationships between biotic abiotic should encourage research. Our ecologically component incorporation into models depend simultaneous quantify situ. author thanks Drs R. T. Koide, S. K. Lucas M. L. McCormack providing feedback previous version manuscript.