What factors influence the diversity of saproxylic beetles? A multiscaled study from a spruce forest in southern Norway

Abstract

The diversity in different groups of obligate saproxylic beetles was related to ecological variables at three levels of spatial scale in mature spruce-dominated forest. The variables were connected to: (i) decaying wood, (ii) wood-inhabiting fungi, (iii) the level of disturbance, (iv) landscape ecology, and (v) vegetational structure. Several strong relationships were found at medium (1.kin 2) and large scales (4 kin2), while only weak relationships were found at a small scale (0.16 ha; I ha --104 m2). This may be explained by the local variations in habitat parameters and the high mobilities of many beetle species. Factors connected to decaying wood and wood-inhabiting fungi were clearly the most important factors at all scale levels. In particular, the variables diversity of dead treeparts, number of dead trees of large diameter and number of polypore fungi species increased the species richness of many groups and increased the abundance of many species. Eight species were absent below a certain density of decaying wood per i or 4 km 2. Former extensive cutting was a negative factor at large scale, probably because of decreasing recolonization with increasing distance to the source habitats. Thinning reduced the diversity of species associated with birch. The development of guidelines favouring the diversity of saproxylic beetles are discussed below.

Species variables or environmental variables as indicators of forest biodiversity: a case study using saproxylic beetles in Maritime pine plantations

“…There are contrasting results on the relevance of physical variables as predictors of saproxylic species richness. Positive correlations between the volume of deadwood and saproxylic beetle richness at the plot level have frequently been observed (Grove, 2002, Martikainen et al, McGeoch et al, 2007Similä et al, 2003;Sippola et al, 2002); however several authors found no relationships between the local amount of deadwood and the richness of saproxylic beetle assemblages (Franc et al, 2007;Økland, et al, 1996;Siitonen, 1994;Similä, et al, 2006;). In our study a portion of the variation in species richness was unexplained by our predictive models.…”

“…The selection of this particular indicator reflects its importance to the 20-25% of forest-dwelling species that are either deadwood dependant or rely on wood-roting fungi, i.e., saproxylic (Elton, 1966;Stokland and Meyeke, 2008). Several studies have shown a significant positive correlation between the amount of deadwood and species richness of saproxylic beetles (Grove, 2002;Jacobs et al, 2007;Martikainen et al, 2000;McGeoch et al, 2007;Økland et al, 1996;Similä et al, 2003;Sippola et al, 2002), wood-inhabiting fungi (Bader et al, 1995;Pentillä et al, 2004;Similä et al, 2006;Stokland et al, 2004), mammals or birds (Mac Nally et al, 2001). Nevertheless, the diversity of deadwood (type, dimension and decay stage) is also an important predictor of saproxylic beetle species richness, as it represents the diversity of possible microhabitats (Ranius and Jonsson, 2007;Siitonen, 2001;Similä et al, 2003).…”

Deadwood and saproxylic beetle diversity in naturally disturbed and managed spruce forests in Nova Scotia

“…Some of these microhabitats are lost because they are found in tree species that are not economically desirable, like aspen (Siitonen and Martikainen 1994) and beech (Nilsson and Baranowski 1997). Others are threatened because they are part of trees with large diameters, which are not maintained amid short-lasting even-age stand rotations (Økland et al 1995;Nilsson et al 1995;Siitonen and Saaristo 2000). Th ese and other factors have lead to concern about the diversity of deadwood microhabitats in general, as defi ned by decay states, sizes, and tree species (Økland et al 1995).…”

Saproxylic beetle (Coleoptera) communities and forest management practices in coniferous stands in southwest Nova Scotia, Canada

“…Saproxylic beetles are a functional group of Coleoptera that depend, at some point in their life cycle, on dead or decaying wood or fungi associated with deadwood (Speight 1989;Økland et al 1996). Not only do these insects comprise a large proportion of total forest species richness, but they also play an important role in decomposition and nutrient cycling in forest ecosystems (Siitonen 2001;Grove 2002b).…”

“…Th ere are few studies of saproxylic invertebrates in eastern Canada compared to many areas of northern Europe (Jonsell et al 1998;Kaila et al 1997;Kolmstrom and Lumatjarvi 2000;Kouki et al 2000;Martikainen 2001;Martikainen and Kouki 2003;Martikainen et al 2000;Muona 1999;Økland et al 1996;Rainius and Jansson 2002;Siitonen 1994Siitonen , 2001Simila et al 2002Simila et al , 2003Sverdrup-Th ygeson and Ims 2002;Vaisanen et al 1993). Only in the last decade have serious investigations of the Nova Scotia saproxylic fauna been undertaken.…”