Decay in Stumps Buried and Submerged Wood

Cut stumps represent a rather special habitat for fungi. The aerial cut surface allows rapid establishment of fungi with air-borne propagules, but also cord-forming basidiomycetes have easy access via dead wood underground (Rayner, 1977a, 1977b; Rayner and Boddy, 1988; Pearce and Malajczuk, 1990). In addition, a variety of fungi that were probably present before felling, e.g. heart rotters such as Ganoderma spp., and latent invaders such as the Ascomycota D. concentrica (on ash) are frequent. Close soil contact buffers environmental fluctuations, making stumps a more stable environment than most other dead wood types. Most fungi causing decay in stumps are equally or more frequent on other dead wood types, but some species seem to take advantage of the special conditions for establishment and growth. The success of H. annosum as a pathogen in conifer plantations is thus partly due to its superior ability for establishment and spread via cut stumps (Woodward et al., 1998), but there are also examples of fungi occurring on deciduous wood which are more common on stumps compared to natural dead wood types (Heilmann-Clausen and Aude, 2006). Buried roots and other subsoil types of dead wood also have a number of Basidiomycota which are very rarely seen on non-buried wood. Some, e.g. Meripilus giganteus, C. fusipes and G. frondosa, seem to be primary decay agents that establish before tree death/felling, while others, e.g. Xerula radicata and Hydropus subalpinus, are likely to be secondary invaders, establishing in dead wood.

Freshwater is present at some forest sites as permanent or temporary ponds and streams. In alder swamp forests, for example, standing water is normal, especially during winter, and a major fraction of the dead wood pool may be inundated for part of the year. Several species seem to be more or less specific to temporarily inundated wood, e.g. Phlebia subochracea and Bulbillomyces farinosus (Winterhoff, 1993). The latter produces vegetative dispersal structures (bulbils) which are probably adapted to dispersal by water. Also some polypores, e.g. Physisporinus vitreus and P. sanguineus, seem to be well adapted to growth under very wet conditions (Schmidt et al., 1997; Aude et al., 2006). Though there are a few aquatic Basidiomycota (Chapter 17), decay of permanently submerged wood is effected almost entirely by Ascomycota and bacteria (Rayner and Boddy, 1988; Kim and Singh, 2000).

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