In 1991, Michael Allen published The Ecology of Mycorrhizae, a fascinating overview of the mutualistic symbiosis between many fungi and almost all plants. It was published when the significance of mycorrhizal associations was on the verge of becoming more widely recognized and appreciated, and a good read for me as a young researcher in fungal ecology. Since then, voluminous research has resulted in a remarkable increase in knowledge and awareness of the ecological significance of this ubiquitous symbiosis, attracting an increasing interest not only from students and scientists, but also from land-use managers and the public. Hence, I was thrilled to read Allen's monumental work compiling and discussing the current state of knowledge in his new publication Mycorrhizal Dynamics, 3 decades later.

The book's premise to explain about mycorrhiza and its significance in the entire ecosystem is very appealing by its connections to theories and accounts of natural history, although I think that some of the more detailed sections may pose greater demands on its readers.

As Allen so effectively conveys, mycorrhiza is no longer described as something odd and of limited importance, as it was in the textbooks of my school days. Instead, mycorrhiza has stepped forward as a basic premise for the existence of plants and terrestrial ecosystems as a whole. It is now recognized as the prerequisite for life's conquest of land 400 million years ago. The subsequent co-evolution of mycorrhizal plants and fungi makes them as tightly intertwined with each other as we are with our gut microbiomes; in both cases, very different types of organisms act as biological and functional units. A thought-provoking perspective is that plants can be considered (merely) as the outcome of a long-standing, successful entrepreneurship with symbiotically associated mycorrhizal fungi in their roots and photosynthesizing cyanobacteria in their foliage. The largely invisible, intimate physiological integration between mycorrhizal plants and fungi, together with fungi being microscopic and located below ground, are the reasons why mycorrhiza has only recently begun to be fully appreciated.

I find it hard to imagine anybody better qualified to synthesize and narrate the overwhelming amount of information on the subject than Michael Allen. In addition to 50 years of research experience of nearly all aspects of mycorrhiza, and having explored the phenomenon in most corners of the world, Allen conveys the current state of knowledge spiced (one might say truffled) with his own experiences in a most curious and captivating fashion. Starting with the early remarkable suggestion of mutualism between ghost pipes and fungi in the late 19th century, the text is pedagogically structured from basic ideas of mycorrhiza and its function to overall perspectives of its ecological significance, both in distinct ecosystems and at the global scale.

Allen invites us to adopt an understanding of mycorrhiza as a dynamic and complex system, in which plants are interconnected with multiple fungi through mycelial networks, and are not to be perceived as single units. His evolutionary and ecological approach makes for a good story line, and I particularly appreciated that the text elaborates on both perspectives—the phytocentric as well as the often-overlooked mycocentric view of mycorrhiza—and in this context also reflects on what an individual means in the realm of fungi. Allen succeeds in revealing how single mycorrhizal associations are integrated through multiple, interconnected networks of diverse plant and fungal compositions, and all the way up to the global scale. He demonstrates how mycorrhiza is a key component in the regulation of atmospheric carbon and also explains how it can play a key role in land management.

I agree with one of Allen's insightful concluding sentences, stating that ‘In the world of mycorrhiza, imagination may be the single most useful tool!’ (p 253). This may seem to detract from the book's extensive scientific content, but it is an apt description of the difficulties we experience when trying to fully grasp or convey the scope of mycorrhiza. The challenge is not only to acknowledge the significance of mycorrhiza, but to transform and integrate its scope into our understanding and perception of nature as a whole—which is made all the more challenging by the fact that mycorrhiza is invisible, being microscopic and located in the soil.

Overall, the book provides an excellent overview with an exhaustive level of detail, shifting between microscopic and global scales, and offering simplified concepts to help us appreciate complex natural histories, with mycorrhiza as a cornerstone of ecosystem functioning. It also provides a much-needed introduction to the effects of climate and environmental change on mycorrhiza, and suggestions for how we can integrate mycorrhizal knowledge into management of forests and agricultural land to mitigate unwanted effects.

Mycorrhizal Dynamics is a great read and has helped me to broaden and update my understanding of the subject. There are few books of its kind, and I recommend it as a valuable resource for researchers and in higher education, and as a worthwhile reference for anybody interested in mycorrhiza. Last but not least, the list of 700 references provides an invaluable resource for those wanting to explore the topic further.