Local Scale Effects

Changes in local habitat composition is most detrimental to species associated with habitats facing a strong decline, while species associated with less declining or even increasing habitats are less negatively or even positively affected. This implies that species depending on large diameter dead wood (standing or lying) are likely to be very sparsely represented in managed forests, while species preferring small diameter dead wood (e.g. attached or fallen branches) and cut dead wood are likely to be frequent (Figure 1). Cut surfaces are interesting as they do not occur under natural conditions, though splintered wood surfaces in fallen trunks and branches are comparable to some degree. As described in Chapter 11, cut surfaces are relatively open resources, inviting establishment of ruderal primary or competitive secondary invading decay fungi to the detriment of latent decay fungi and heart-rot agents.

Several studies have compared the species composition among dead-wood habitats along the gradient from natural to managed forests, but mostly in boreal coniferous forests (e.g. Bader et al., 1995; Sippola and Renvall, 1999; Pentilla et al., 2004; Junninen et al., 2006). Logging waste and cut stumps in managed forest attracted species that were infrequent in natural forests (Sippola and Renvall, 1999; Pentilla et al. 2004). These included species confined to early stages of wood decay, for example Stereum sanguinolentum, but also a number of species preferring cut stumps, for example Porpomyces mucidum, Postia fragilis, P. stiptica,

Figure 1 Location and type of dead wood in managed (top) and natural forests (lower). Underlined texts indicate wood types largely restricted to either situation, while non-underlined texts indicate wood types that occur in both managed and unmanaged stands. (Source: Modified from Heilmann-Clausen (2005b).) See also Figure 2.

Figure 1 Location and type of dead wood in managed (top) and natural forests (lower). Underlined texts indicate wood types largely restricted to either situation, while non-underlined texts indicate wood types that occur in both managed and unmanaged stands. (Source: Modified from Heilmann-Clausen (2005b).) See also Figure 2.

Figure 2 Dead wood habitats differ markedly among sites depending on management history. (1) Natural forests with minimal signs of any management contain a variety of dead wood habitats, including fallen logs, branches and twigs as well as attached dead wood, mostly subject to shady and cool conditions. (a) Beech (Fagus sylvatica) forest at Fontainebleau, France. (b) Mixed deciduous forest in Suserup Skov, Denmark. (2) Forests managed for timber production have little dead wood, mainly occurring as fallen or cut branches and twigs, cut stumps and attached dead wood. (c) Managed beech forest near Silkeborg, Denmark (© Jacob Heilmann-Clausen). (3) Large, well spaced, often pollarded veteran trees, are often prominent along roadsides and rivers and in wood pasture. Such trees typically have attached dead components and contain heart rots supporting stress-tolerant fungi adapted to decay in living, often sun-exposed wood. Due to a pronounced competition for light and space similar veteran trees are mostly infrequent in natural forest. (d) Beech pollards from Bertizarana in Navarra, northern Spain. (e) Beech pollard from Epping, U.K.

Source: (a) © Morten Christensen; (b, c and d) © Jacob Heilmann-Clausen; (e) © Martyn Ainsworth. (See Colour Section)

Figure 2 Dead wood habitats differ markedly among sites depending on management history. (1) Natural forests with minimal signs of any management contain a variety of dead wood habitats, including fallen logs, branches and twigs as well as attached dead wood, mostly subject to shady and cool conditions. (a) Beech (Fagus sylvatica) forest at Fontainebleau, France. (b) Mixed deciduous forest in Suserup Skov, Denmark. (2) Forests managed for timber production have little dead wood, mainly occurring as fallen or cut branches and twigs, cut stumps and attached dead wood. (c) Managed beech forest near Silkeborg, Denmark (© Jacob Heilmann-Clausen). (3) Large, well spaced, often pollarded veteran trees, are often prominent along roadsides and rivers and in wood pasture. Such trees typically have attached dead components and contain heart rots supporting stress-tolerant fungi adapted to decay in living, often sun-exposed wood. Due to a pronounced competition for light and space similar veteran trees are mostly infrequent in natural forest. (d) Beech pollards from Bertizarana in Navarra, northern Spain. (e) Beech pollard from Epping, U.K.

Source: (a) © Morten Christensen; (b, c and d) © Jacob Heilmann-Clausen; (e) © Martyn Ainsworth. (See Colour Section)

Phlebiopsis gigantea and the pathogenic Heterobasidion parvisporum. The list of species more or less confined to natural forests was much longer including a number of proposed old-growth indicators, for example Amylocystis lapponica, Fomitopsis rosea and Phellinus ferrugineofuscus all confined to decaying logs.

In deciduous forests there is also evidence that cut stumps and tree tops left after cutting develop different communities of decay fungi than in wood made available more naturally. In a study of Danish beech forests cut stumps hosted sporocarps of the pyrenomycetes Kretzschmaria deusta and Xylaria hypoxylon, and the agaric Kuehneromyces mutabilis significantly more often than other types of dead wood (Heilmann-Clausen and Aude, 2006). Tree tops left after cutting similarly hosted a number of pyrenomycetes, for example Eutypella quaternata and Hypoxylon spp., but also some aphyllophorales, for example Skeletocutis nivea and Hyphodontia paradoxa, which were significantly less frequent on decaying logs. Logs situated in natural forests hosted sporocarps of a number of species which were practically absent from cut tree tops and stumps, such as polypores causing heart-rot, for example Fomes fomentarius, Ganoderma lipsiensis and Ischnoderma resinosum, but also cord-formers, for example Lycoperdon pyriforme, L. perlatum and Ramaria stricta, and late stage agarics, for example Mycena haematopus, Galerina marginata and Psathyrella piluliformis.

In conclusion, communities of wood-decay fungi in managed forests have different composition to those in more natural forests. Stress tolerant heart-rot fungi and other species involved with decay of fallen logs are much less frequent in managed forest, whereas ruderal/competitive species infecting through cut surfaces are abundant.

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