Ectomycorrhizal fungi – potential organic matter decomposers, yet not saprotrophs

Summary Although hypothesized for many years, the involvement of ectomycorrhizal fungi in decomposition of soil organic matter remains controversial and has not yet been fully acknowledged as an important factor in the regulation of soil carbon (C) storage. Here, we review recent findings, which support the view that some ectomycorrhizal fungi have the capacity to oxidize organic matter, either by ‘brown‐rot’ Fenton chemistry or using ‘white‐rot’ peroxidases. We propose that ectomycorrhizal fungi benefit from organic matter decomposition primarily through increased nitrogen mobilization rather than through release of metabolic C and question the view that ectomycorrhizal fungi may act as facultative saprotrophs. Finally, we discuss how mycorrhizal decomposition may influence organic matter storage in soils and mediate responses of ecosystem C sequestration to environmental changes. Contents Summary 1443 I. Introduction 1443 II. New insights from genomics, transcriptomics and spectroscopy 1444 III. What do mycorrhizal fungi gain from decomposition? 1445 IV. Ectomycorrhizal fungi as regulators of soil C dynamics 1446 V. Conclusions 1446 Acknowledgements 1446 References 1447