A book about trees and fungi, what’s not to like?*

Fungi and trees: Their complex relationships, by Lynne Boddy, 2021. Arboricultural Association.

Arbor is the borrowed-from-Latin word for a tree. You’d therefore expect a book from the UK’s Arboricultural Association to say a thing or two about trees. But, as Lynne Boddy notes in Fungi and trees** (which tome is here appraised), one should “Never think of a tree as just a tree: Always, think tree plus very many fungi, and other organisms” (page iii). As befits its title, Fungi and trees doesn’t consider the ‘other organisms’ in much detail, but it does have a lot to say about fungi and trees.

As the back cover declares, Boddy’s book is “aimed at anyone who is interested in trees or fungi”. ‘Anyone’ makes for a very wide-ranging readership. It is therefore important to pitch the information – which can often be quite technical – with enough detail to make it useful, but not so much that it’s a turn-off for the intended readers. And added to that is the need to make the text readable and accessible for as wide a readership as possible. Has Boddy achieved those goals?

First things first…

As a botanist in the 21^st century who likes to think of himself as reasonably fungi-literate, the first thing I wanted to check was whether Fungi and trees had anything to say about the wood–wide web [the WWW]. It did: This amazing underground network that connects trees to fungi was given a good airing on pages 74-75, and 78, with a graphic of the phenomenon on page 75. The second was to see if fungus-like organisms such as Phytophthora were mentioned, and how they were treated. As biological agents causing serious disease in plants (including trees), the Oomycota – the group of organisms to which Phytophthora belong – is included, and its distinction from members of the Kingdom Fungi clearly stated. Good, although this wasn’t too unexpected. After all, it would be unforgivable for a fungologist to refer to them as fungi(!) Having passed these two tests, all appeared to bode well for Boddy’s book, and was a good start to my assessment of Fungi and trees. And, I’m pleased to say, my continued scrutiny of the text increased my overall appreciation for what Boddy has achieved.

Overview of book

The major part of Fungi and trees is contained within 10 chapters, each of which begins with a summary of its content – which is always nice to see and help one appreciate what’s coming up. By way of scene-setting, Chapter 1 deals with fungal basics, and Chapter 2 covers the biology of tree and shrubs that is most relevant to the fungus interactions. Chapter 3 looks at beneficial tree-fungus interactions (including the WWW and lots of different mycorrhizae). Chapter 4 –‘Fungi that harm trees’ – sets the scene for further detailed consideration of this interaction in Chapters 7 on heart-rot and hollowing, and Chapter 8 on sapwood decay. Chapter 5 looks beyond trees and fungi in looking at interactions between tree-associated fungi and other organisms. Chapter 6 provides important insights into the wood-decaying role of fungal communities. All of this fungal activity takes place against a background of great environmental change, and Chapter 9 provides more detail of the effects of such factors as land use change, climate change, chemical pollution, and CO₂ effects – which makes for quite a sobering read.

Finally, and notwithstanding the negative connotations of disease-causing that mention of fungi in the context of trees usually generates, the book’s last chapter looks at what can be done to encourage and achieve fungus conservation. As the book makes abundantly clear, this is an important topic as it is primarily the decomposing action of fungi on trees that releases nutrients back into the community for the ultimate benefit of all inhabitants of that ecosystem, including the establishment and growth of new trees. Fungi and trees is therefore more than just a book about trees and fungi, it’s an important book about woodland ecology (albeit with an emphasis upon fungi and trees…), and the understanding and effective management of these important natural resources.

Although Boddy’s book can be quite technical – in places it does read like a textbook – its engaging writing style, and the veritable forest of fungus facts, helps one to persevere and overcome any hindrance that might otherwise present. Providing further help with accessibility, Fungi and trees is abundantly illustrated throughout with photographs, micrographs, and diagrams, and there is a profusion of tables and ‘boxes’ to expand upon the information in the text.

Lots of new information

Not only is there a lot of information packed into its 288 main text pages, but many of Boddy’s fungus facts were new to me. For example: the concept of ‘phoenix trees’; the notion of mycorrhizal ‘helper bacteria’; the fact that hyphae of some lichen fungi, ostensibly living epiphytically and therefore ’harmlessly’ upon trees, can penetrate their bark and enter the xylem and phloem (although this can apparently permit fungus-derived chemicals to enter the tree’s vascular system, Boddy is silent on whether the fungus/lichen obtain waters and/or sugars from these tree tissues); the connection between fungus-derived VOCs [volatile organic compounds] (Arati Inamdar et al., Fungal Volatile Organic Compounds: More Than Just a Funky Smell? Annual Review of Microbiology 74: 101-116, 2020; https://doi.org/10.1146/annurev-micro-012420-080428) and sick building syndrome; the potential for use of mycoparasites – fungi that are parasitic upon other fungi – as biocontrol agents against tree-harming fungi, and the use of viruses that infect fungi – mycoviruses (Moonil Son et al. (2015) Five Questions about Mycoviruses. PLoS Pathog 11(11): e1005172. https://doi.org/10.1371/journal.ppat.1005172) – as a biocontrol against chestnut blight; that both C:N and C:P ratios in wood are improved by fungal activity during its decomposition so that its food value to saproxylic invertebrates is enhanced; the larvae of some insects spin webs beneath bracket fungi that catch falling spores (which are presumably eaten); the fact that some fungi have specialised structures – stephanocysts (Harold H Burdsall, Jr, Stephanocysts: Unique Structures in the Basidiomycetes, Mycologia 61(5): 915-923, 1969; https://doi.org/10.2307/3757636; JY Liou & SS Tzean, Stephanocysts as Nematode-Trapping and Infecting Propagules, Mycologia 84(5): 786-790, 1992; doi: 10.1080/00275514.1992.12026205) – that kill nematodes, collembola and other small invertebrates; the revelation that fungus-decayed wood in southern Chile is used as cattle fodder; and an introduction to the concept of ‘salvage logging’.

Sources…

If, like me, you find it refreshing to learn new things, Fungi and trees will not disappoint. And much of what I learned I’d like to include in my own writing efforts, as appropriate. However, because of the book’s layout it’s not easy to unearth the definitive source for specific facts: There are no in-text references. Instead, there is a list of Further Reading – which includes books, scientific articles, web-sites, and videos – at the end of each chapter. This absence of a direct link between in-text facts and their sources means one has to trust that the author has presented the work/words of others correctly [and there can be issues with that approach as discussed here]. Whilst I have no reason to doubt Boddy’s integrity and veracity in reporting work from the literature, as one who tries to promote evidence-based writing it would be really helpful to know the sources used for the information presented so I can give the appropriate credit if sharing the fascinating fungal facts with others. However, one notes – and applauds – the inclusion of citation details in the legends to many of the figures and tables (which sources are often additional to those listed as further reading).

Indexes and Glossary

To help find information within the book, Fungi on trees includes 3 indexes, for Subjects (from abscission to Zygomycota), for genera and species of fungi (from Acaromyces to Xylospora friesii), and for genera and species of trees and shrubs (from Abies to Yucca) [neither of which taxonomic Index includes common names for the taxa included]. Unfortunately, my favourite of the book’s many named fungi – Zeus olympius (mentioned on page 265) – wasn’t listed in any of the indexes. Almost inevitably in a book that deals with quite complex material, a lot of technical terms have to be used. Pleasingly, they are usually either explained in-text or in the Glossary – and sometimes both. However, I think the term ‘radionuclide’ (on page 248) needs to be in the Glossary – or explained in text – for the benefit of readers. And the Glossary entry for ‘cork cambium’ (page 289) – which is here defined as “a tissue found in  the bark of some trees that forms new epidermal cells” – needs to be corrected.

Fungi and trees, it’s a bit complicated

As the book’s sub-title has it, the relationship(s) between fungi and trees is truly complex. It’s also imperfectly understood. Reading Lynne Boddy’s fascinating book gives some insight into how complex that tree-fungus relationship can be, which complexity is further increased when you take account of fungus interactions with bacteria, viruses, protists, invertebrates, and vertebrates (as the book does). But, having read Fungi and trees, and appreciated the wealth of examples that inform its subject matter, it is easy to agree with the author’s view that: “Clearly, we must raise public and political awareness of the need to protect tree-associated fungi and to include them along with plants and animals in national, continental and global conservation strategies” (page 264). Boddy’s superb book should go a long way towards raising awareness of the important role of tree-associated fungi amongst the public – assuming they read it. One can only hope and trust that awareness of those with political influence to make a difference in such matters is also raised – and acted upon.

Summary

Coming back to the question posed at the start of this blog item, is Lynne Boddy’s Fungi and trees’ “aimed at anyone who is interested in trees or fungi”? Yes, and it hits its target. Any- and everyone – whether they regard themselves as fungi-literate or are completely myco-deficient – should get a lot from this splendid and informative book that is both readable and accessible.

* This post is Mr P Cuttings’ contribution to UK Fungus Day 2021.

** Although I’m not officially appraising Fungi on trees: A photographic reference by David Humphries and Christopher Wright, this tome deserves a ‘shout-out’ in this blog post. Billed as “A must have reference, featuring in-depth biographies of 100 species of fungi found on trees”, this book contains over 900 colour photographs of both annual and perennial fungi (and slime moulds) that are associated with trees. It is promoted as a companion volume to Fungi and trees, and is a great visual accompaniment to Boddy’s tome. That companionship is underlined by the fact that their publisher, the Arboricultural Association, offers both books as a ‘bundle’, with a cost-saving on purchasing both separately. As one who has looked over Fungi on trees, I can confirm that it is a formidable photographic fungusfest featuring the good, the bad, and the bizarre of tree-associated fungi (and slime mould).