Fungal Strategies of Wood Decay in Trees
Springer Science & Business Media, 2000 - Nature - 185 pages
Wood-destroying fungi play an important role in nature, because they are the only forms of life capable of reducing wood to its initial constituents. However, they can also be dangerous for people and property, as they can impair the stability and fracture-safety of trees.
This book gives detailed information, based on new and original scientfic findings, on the examination and effects of the most important species of fungi associated with failure of infected urban trees. In addition, new ways are presented for predicting the advance of decay in the living tree. The subject is illustrated and made easily accessible by numerous colored photos of fungus fruit bodies, defect symptoms, and macroscopic and microscopic pictures of wood decay. A detailed introduction to the fundamentals of wood pathology provides a way into the subjects of applied mycology and tree care for readers without previous special knowledge. Francis W.M.R. Schwarze, National Diploma of Arboriculture at Merrist Wood College, UK (1991), Master of Science in Pure, Applied Plant and Fungal Taxonomy, University of Reading, UK (1992), doctorate at Freiburg University (1995), since 1996 assistant at the Institute for Forest Botany and Tree Physiology at Freiburg University, concentrating on research into wood-destroying fungi and host-fungus interactions.
Julia Engels, Diploma Forester at Freiburg University (1995), doctorate on root fungi at Freiburg University (1998). Since 1998 active in tree care and mycology in Luxembourg.
Claus Mattheck, born 1947, doctorate in theoretical physics (1973), qualified as lecturer on damage studies at Karlsruhe University (1985), and now teaches there as Professor. Since 1991 he has been an officially appointed and attested expert on tree mechanics and fracture behaviour. Has been awarded numerous prizes for research and publication. Head of the Biomechanics Department at the Karlsruhe Research Centre.
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In 1878, in Germany, as I learned in Forestry 101, the modern science of tree care was born with the publication of Robert Hartig’s text on tree disease. This landmark book described the parasitic mode of life of Armillaria on Scots pine and documented the breakdown of cell walls by Phellinus pini. In 1863, Schacht had described the invasion of cell walls by fungal hyphae. Lacking the tools necessary for a closer analysis, but building on Schacht’s work, Hartig postulated that enzymes secreted by fungal hyphae dissolved lignin and caused secondary cell walls to collapse. As a result, wood would become worthless, and trees would fall down.
In 2000, in Germany, the science of tree care took a great leap forward. Building on the work of Hartig, Shigo and many others, Francis W.F.M.R. Schwarze, Julia Engels and Claus Mattheck published Fungal Strategies of Wood Decay in Trees. Now available worldwide, and made readily accessible to English speakers thanks to the superlative translation work of William Linnard, this book shows the reader an entirely new way of looking at decay in trees. By understanding fungus-tree interaction more completely, the tree manager can make decisions about how to handle infected trees with more certainty.
More certainty is certainly needed today. Many authorities tell tree managers that infections by Armillaria, Ganoderma, Inonotus and other fungi are considered sufficient cause for immediate removal of the tree for fear of failure. However, based on over ten years of research, Schwarze tells us “…the mere occurrence of a fungus fruit body on a tree does not indicate the extent of the decay…Degradation processes, host differences and environmental conditions are too diverse…decays often affect only a small amount of wood in the tree, so that stability and safety are not impaired.”
The book begins with a review of wood anatomy, focusing on the layered structure of the cell wall. Readers of Mattheck’s earlier work will recognize the hedgehog demonstrating the mechanical stresses within the tree. By listening to this “body language” spoken inside the tree, the diagnostician may “hear” the decay spread--and sometimes stop. With magnification up to 1000x, the reader is able to see clearly the action of the fungus in the cells, and the reaction of the trees to the attack.
Fungal pathology is reviewed next; the brown, white and soft rots. Much advanced information on soft rots, which were first described by Schacht in 1863, is presented. For instance, research by Schwarze et al prove what Sinclair, Lyon and Johnson saw indications of in 1987—that Hypoxylon deustum (a.k.a. Ustulina deusta) causes a soft rot in the sapwood of various trees. This is just one example of a pathogen shifting strategies, from saprophyte to parasite, or from enzyme-secreting to hyphae-growing that the authors note, especially on moisture-stressed trees.
Chapter Three, the heart of the book, is devoted to Fungus-Host Combinations. For a diagnostician of limited understanding, such as the reviewer, the illustrations here tell the tale of fungal pathology better than a thousand words. First, electron micrographs take the eye into intercellular and intracellular space, where the chemical battles take place. Then, three-dimensional anatomic drawings paint a distinct picture of the disease and the defense. Finally photographs, of standing trees and cross-sections, show what we all see in real life when a rotting tree is cut down and cut up.
By pulling the eye and the mind from the inside of the tree to the outside and back again, the book allows the reader to exhaustively examine what takes place when fungus and tree combine. Still, as Schwarze says, “it requires an effort to understand these…’trials of strength’…the only sensible approach to predicting the future expansion of a decay…” Or termination of a decay process; for he and others have observed, “many trees, old and young, in which a decay has been successfully compartmentalized”. The