Abstract
ContextDead wood is a key habitat for saproxylic species, which are often used as indicators of habitat quality in forests. Understanding how the amount and spatial distribution of dead wood in the landscape affects saproxylic communities is therefore important for maintaining high forest biodiversity.ObjectivesWe investigated effects of the amount and isolation of dead wood on the alpha and beta diversity of four saproxylic species groups, with a focus on how the spatial scale influences results.MethodsWe inventoried saproxylic beetles, wood-inhabiting fungi, and epixylic bryophytes and lichens on 62 plots in the Sihlwald forest reserve in Switzerland. We used GLMs to relate plot-level species richness to dead wood amount and isolation on spatial scales of 20–200 m radius. Further, we used GDMs to determine how dead wood amount and isolation affected beta diversity.ResultsA larger amount of dead wood increased beetle richness on all spatial scales, while isolation had no effect. For fungi, bryophytes and lichens this was only true on small spatial scales. On larger scales of our study, dead wood amount had no effect, while greater isolation decreased species richness. Further, we found no strong consistent patterns explaining beta diversity.ConclusionsOur multi-taxon study shows that habitat amount and isolation can strongly differ in the spatial scale on which they influence local species richness. To generally support the species richness of different saproxylic groups, dead wood must primarily be available in large amounts but should also be evenly distributed because negative effects of isolation already showed at scales under 100 m.
Highlights
Biodiversity is declining globally as a consequence of climate and land-use change (Sala et al 2000; Rockstrom et al 2009; Steffen et al 2015; IPBES 2019)
To generally support the species richness of different saproxylic groups, dead wood must primarily be available in large amounts but should be evenly distributed because negative effects of isolation already showed at scales under 100 m
We found significant positive relationships between dead wood amount and species richness, but the species groups differed in the spatial scales at which this effect manifested (Fig. 3, Tables S3–S6)
Summary
Biodiversity is declining globally as a consequence of climate and land-use change (Sala et al 2000; Rockstrom et al 2009; Steffen et al 2015; IPBES 2019). While tropical forests are disappearing rapidly, European forests have been expanding since the 1990s but are often intensively managed (Bryant et al 1997; FAO 2010) This leads to a severe underrepresentation of old successional stages in many regions (Vilen et al 2012) and a decline of species that depend on old-growth forest characteristics such as large amounts of dead wood and old trees (Brunet et al 2010; Paillet et al 2010; Eckelt et al 2018). In temperate and boreal regions, 20–25% of forest species depend on the availability of dead wood (= saproxylic species; Stokland et al 2012), which makes it a key element for biodiversity conservation in forests (MCPFE 2003; Stokland et al 2012). For the development of appropriate management concepts, research on key elements supporting biodiversity is needed
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