Knowledge of community development in standing dead trunks is limited. In boreal Fennoscandia dead pine trees, known as kelo-trees, may stand for centuries and have been reported to support highly specialized fungal communities (Niemela et al., 2002). Data from managed Danish beech forests similarly indicate natural snags have a distinctive mycoflora based on sporocarp observations (Heilmann-Clausen and Aude, 2006). For instance, the heterobasidiomycetes Phleogena faginea was very prominent, occurring on 29% of investigated snags, but only on 2% of the fallen logs. When long standing snags or standing dead trees fall to the ground they support fungal communities different from logs in the same decay stage which have decomposed on the ground. Several polypores and tooth fungi of conservation interest seem to fruit preferentially on such fallen dry trees or snags (Heilmann-Clausen and Christensen, 2004), but statistically supporting data are lacking.
Sun-exposed wood in standing trunks will experience extreme temperature fluctuations. Interestingly, some isolates of the rare heart rot agent P. quercinus, usually found in oak trees in wood pasture, grow well at 30 °C (Wald et al., 2004), and we hypothesize that tolerance to high temperatures and/or desiccation is common among species living in standing dead wood. In this respect it is noteworthy that a compiled list of wood decay fungi from road side trees in Germany is remarkably rich in heart rot fungi and other species associated with decay in living trees (Kreisel, 2000). Several of the reported species, e.g. Inonotus nidus-pici, I. hispidus, Ganoderma adspersum and Sarcodontia crocea, are very sparsely recorded from forest environments in the same region and it seems likely that many of them are tolerant of heat-stress with low competitive ability in more shaded conditions.
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