page_title: Wood-decay fungus
section_title: Brown rot
hierarchical_section_title: Wood-decay fungus / Brown rot
caption_attribution_description: English: Cubical rot, checked, on quercus, Białowieża forest, Poland Dansk: Terningeformet brunråd på en eg i Bialowieza-skoven, Polen.
context_page_description: A wood-decay fungus is any species of fungus that digests moist wood, causing it to rot. Some species of wood-decay fungi attack dead wood, such as brown rot, and some, such as Armillaria, are parasitic and colonize living trees. Excessive moisture above the fibre saturation point in wood is required for fungal colonization and proliferation. Fungi that not only grow on wood but permeate its fibrous structure and actually cause decay, are called lignicolous fungi. In nature, this process causes the breakdown of complex molecules and leads to the return of nutrients to the soil. Various lignicolous fungi consume wood in various ways; for example, some attack the carbohydrates in wood and some others decay lignin. The rate of decay of wooden materials in various climates can be estimated by empirical models.
  Wood-decay fungi can be classified according to the type of decay that they cause. The best-known types are brown rot, soft rot, and white rot. Each produce different enzymes, can degrade different plant materials, and can colonise different environmental niches. The residual products of decomposition from fungal action have variable pH, solubility and redox potentials.
context_section_description: Brown-rot fungi break down hemicellulose and cellulose that form the wood structure. Cellulose is broken down by hydrogen peroxide (H₂O₂) that is produced during the breakdown of hemicellulose. Because hydrogen peroxide is a small molecule, it can diffuse rapidly through the wood, leading to a decay that is not confined to the direct surroundings of the fungal hyphae. As a result of this type of decay, the wood shrinks, shows a brown discoloration, and cracks into roughly cubical pieces, a phenomenon termed cubical fracture. The fungi of certain types remove cellulose compounds from wood and hence the wood becomes a brown colour.
  Brown rot in a dry, crumbly condition is sometimes incorrectly referred to as dry rot in general. The term brown rot replaced the general use of the term dry rot, as wood must be damp to decay, although it may become dry later. Dry rot is a generic name for certain species of brown-rot fungi.
  Brown-rot fungi of particular economic importance include Serpula lacrymans (true dry rot), Fibroporia vaillantii (mine fungus), and Coniophora puteana (cellar fungus), which may attack timber in buildings. Other brown-rot fungi include the sulfur shelf, Phaeolus schweinitzii, and Fomitopsis pinicola.
  Brown-rot fungal decay is characterised by extensive demethylation of lignins whereas white-rot tends to produce low yields of molecules with demethylated functional groups.
  There are very few brown rot fungi in tropical climates or in southern temperate zones. Most brown rot fungi have a geographical range north of the Tropic of Cancer (23.5° latitude), and most of these are found north of the 35° latitude, corresponding to a roughly boreal distribution. Those brown rot fungi between latitudes 23.5° and 35° are typically found at high elevations in pine forest regions, or in coniferous forest regions such as the Rocky Mountains or the Himalayas.
caption: Cubical brown rot on oak
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