Stand And Landscape Level

Looking at the decay community at the forest stand level gives another perspective to wood decay. At this scale, individual logs contribute to a dynamic network of resources. The important question then is whether there is a continuum of resources large enough to support the community or if fluctuations in resource availability will cause local extinctions and recolonization events. Berglund and Jonsson (2003) showed that there is a high degree of nestedness in the occurrence of wood-decay fungi at the stand level, or in other words, small habitats will contain a subset of the species pool of large habitats. Ecological theory tells that the extinction of species is more likely to occur in small habitats than in larger. The persistence of some species is definitely affected by gaps in the continuation of available resource at the stand level (Stokland and Kauserud, 2004). In addition, local dispersal sources (within 3 km) may strongly affect colonization patterns of red-listed wood-decaying fungi (e.g. Fomitopsis rosea) in spruce (Edman et al., 2004b, 2004c), and within 1 ha areas, decay fungi seemed not to be dispersal limited (Rolstad et al., 2004). Sverdrup-Thygeson and Lindenmayer (2003) reported that the presence and abundance of Phellinus nigrolimitatus were strongly and positively correlated with the area of forest uninterrupted by major disturbance in the past 240 years (equalling 140 years of 'old growth continuity') in the surrounding landscape (80 ha). In contrast, Groven et al. (2002) failed to find a positive correlation between the abundance of indicator fungi and continuity of dead wood (number of old logs present) at stand scale, but this could be due to the fact that they did not have good-continuity plots in their study. Taken together, the evidence is clear that anthropogenic influences have reduced the resource availability by 90% (Siitonen, 2001). The disturbance caused by forestry is likely to affect more severely species in later stages of succession (e.g. Stokland and Kauserud, 2004) and those with small populations. Fungal species specialized for large logs have suffered (e.g. Bader et al., 1995; Kruys et al., 1999; Penttila et al., 2004; Stokland and Kauserud, 2004) since, especially, such logs are removed from managed forests. In a comparative study of species richness in old-growth spruce and managed spruce stands, Penttila et al. (2004) showed that old-growth stands on average contained 80% more polypore species than mature managed stands. Threatened species were confined to old-growth stands and to managed stands where the amount of dead wood exceeded 20 m/ha. Lindblad (1998), Jonsson and Jonsell (1999) and Sippola et al. (2001) also found that the species richness and number of red-listed polypore species are much higher in old-growth forests than in managed forests. In another study comparing forest landscapes east and west of the Finnish Russian border in Karelia, strikingly higher numbers of species were found on the eastern side with higher amounts of dead wood and higher continuity between high quality habitats (Siitonen et al., 2001). In addition, Edman et al. (2004c) and Penttila et al. (2006) have shown that both the deposition of spores and occurrence of fruit bodies in rare spruce-living polypore species are highly dependent on the forestry and fragmentation history at landscape level (see also Chapter 13).

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