The Actions of Fungi in Ecosystems

I was a zoology major as an undergraduate student. I had not thought at all about fungi until I took an introductory ecology course in my second year, taught by a fungal ecologist who was clearly trying to shake us up when he asked this question in class: What are the minimum requirements for a functioning ecosystem? I didn't think much about the question, but the answer certainly got my attention. Necessary components for a functioning ecosystem included primary producers (plants) and decomposers (bacteria and fungi), but not animals. Clearly, the question was designed to get us out of our normal animal-centered thinking and make us realize that other organisms, such as fungi, also play vital roles. That lecture was my first exposure to the importance of fungi in the cycling of materials and energy, and it was a pivotal moment in my career. I went on to study fungal biology and ecology, and I have devoted my time to the subject ever since. Fungi are ubiquitous, even in extreme environments; they are very diverse taxonomically and phylogenetically, and provide a wide variety of ecosystem services. Arguably, their most important function is as agents of biogeochemical cycling. The ability of saprobic fungi to decompose complex substrates makes them astonishingly important for turnover of materials. Of course, we must remember that other fungi that influence the cycling of energy and materials are not considered saprobes. They include mutualists, parasites, and pathogens, and they also have diverse functions. Many books have been published on fungal biology, but few on fungi's role in ecosystem processes (an exception being John Dighton's Fungi in Ecosystem Processes). The topic is becoming increasingly important, especially the study of biogeochemical changes resulting from such influences as climate change, land-use change, and invasion by exotics. The field is advancing very quickly, so a book such as Fungi in Biogeochemical Cycles is timely. Geoffrey Gadd, the book's editor, is a professor of microbiology at the University of Dundee and a leading researcher in basic and applied microbial biogeochemistry. His work focuses primarily on determining the microbial-mediated mechanisms for metal mobility in natural and contaminated ecosystems. Gadd has gathered an excellent set of authors, all leaders in their various fields and in particular fungal groups, to summarize current research and to highlight the roles of fungi in biogeochemical cycles. The contributors offer a balance between processes involving fungi in natural systems and those in contaminated systems. Overall, the book provides a good summary of the actions of saprophytic and mycorrhizal fungi, as well as some lichen-associated fungi. I am glad that in some chapters bacteria are discussed in comparison, as they are also highly relevant. All these organisms are well linked to biogeochemical processes—among others, mineral transformations and transport, nutrient cycling, water dynamics, and degradation of complex materials such as polycyclic aromatic hydrocarbons and polymers. There is good coverage across different ecosystem types, such as soil, freshwater, marine, and estuary systems. The particular strength of Fungi in Biogeochemical Cycles is its balance among the “bio,” “geo,” and “chem” components of biogeochemistry. Although I am enthusiastic about the book because of the excellent individual contributions, I do see some shortcomings. First, I would have liked more continuity from chapter to chapter. Although authors do refer to information in other chapters, a better synthesis could have been achieved by having an introductory chapter that discussed the book's goals and intended “deliverables.” Similarly, a final chapter that summarized the various contributions would have helped. In my opinion, all multi-author volumes should have such editor-written, synthesizing chapters. Another limitation of the book is that it largely ignores the indirect contributions of fungal parasites and pathogens. These latter functional groups are also ubiquitous in ecosystems, and can exert a profound influence by affecting the activities of primary producers and other organisms. Overall, I highly recommend this volume, not just to the mycologist but also to the ecologist, geologist, environmental scientist, and earth scientist. It will be especially useful to senior undergraduates and graduate students in interdisciplinary fields such as ecosystem ecology and biogeochemistry. Perhaps some of them will discover their own enthusiasm for fungi and become convinced—as I was—of the importance of this often-overlooked group of organisms in the functioning of ecosystems.

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