Spatial pattern in the occurrence of the lichen Lobaria pulmonaria in managed and virgin boreal forests

Abstract

Two populations of the lichen Lobaria pulmonaria, growing on aspens and goat willows in 12 and 20 km2 study areas of boreal forest in Finland, were surveyed thoroughly to investigate the factors influencing the spatial distribution of the lichen. In one study area, where forestry has been intensive and old‐growth forest is highly fragmented, L. pulmonaria was sparse and grew mostly on willows. In contrast, a large and continuous virgin forest area supported a higher incidence of L. pulmonaria, with the lichen being common on both aspens and willows. In both study areas, the distributions of aspen and willow were clumped over the scales of 100–1000 m. The spatial pattern of L. pulmonaria was more clumped in the managed forest than in the virgin forest. The reduced incidence of the lichen on aspens in the managed area was attributed to a disruption of habitat continuity and small average tree size. There was no comparable reduction in the incidence on willows, probably because the willow had a very aggregated distribution in the managed area, which probably facilitated local colonization of the lichen. Presence of the lichen was significantly related to size‐corrected local density of aspen and willow trees as well as to spatial connectivity to neighboring lichen‐occupied trees.

Fine spatial pattern of an epiphytic lichen species is affected by habitat conditions in two forest types in the Iberian Mediterranean region

“…The spatial pattern of lichen occurrence was independent of the distribution of suitable habitat. This was also shown for L. pulmonaria in boreal forests, suggesting that the microhabitat quality determines establishment (Gu et al 2001;Óckinger et al 2005;Werth et al 2006). Dispersed propagules land on sites within a few metres of the dispersal source and this is independent of habitat quality (Edman et al 2004;Werth et al 2006;Jonsson et al 2008).…”

“…Epiphytes are influenced by their substrate, so analysis of the spatial pattern of epiphytic lichens may be controlled by the underlying distribution of their host trees (Gu et al 2001;Hedenás et al 2003). We analysed the spatial pattern of beech and oak trees using Ripley's K-function (Ripley 1988).…”

“…Epiphytes need to track and respond to these dynamic patches to persist at different hierarchical spatial scales (Snail et al 2003(Snail et al , 2005. Epiphytes can respond to the spatial configuration of forest remnants (Snail et al 2004;Óckinger et al 2005), including the matrix structure (Belinchón et al 2009), and they can respond to tree stand configuration and structure at a lower nesting of the spatial scale (Gu et al 2001;Hedenás et al 2003).…”

“…However, distance-dependent dispersal cannot be ignored (Walser 2004;Óckinger et al 2005;Pharo & Zartman 2007;Johansson 2008). A growing body of literature is devoted to assess the influence of the nearest tree distance on the dynamics of epiphytic populations (e.g., Gu et al 2001;Kalwij et al 2005;Snail et al 2005;Bolli et al 2008). It remains unknown how dispersal actually limits and regulates the distribution of epiphytes, and how it interacts with habitat structure and quality (Heegaard & Hangelbroek 1999;Scheidegger & Werth 2009).…”

“…It remains unknown how dispersal actually limits and regulates the distribution of epiphytes, and how it interacts with habitat structure and quality (Heegaard & Hangelbroek 1999;Scheidegger & Werth 2009). Gu et al (2001) indicated that the distance between a noncolonized tree and the nearest colonized neighbouring tree provides a measure of the likelihood of colonization.…”