Effects of Stand-Level Disturbances on the Spatial Distribution of a Lichen Indicator

Abstract

Due to its assumed dispersal limitation and susceptibility to disturbance, the epiphytic lichen Lobaria pulmonaria is used as an indicator of undisturbed forest stands. The hypothesis was tested that stand‐level disturbances have a long‐lasting negative impact on the occurrence of L. pulmonaria. Two 19th century stand‐level disturbances were reconstructed using aerial photographs from 1933. For 7769 potential host trees within a random sample of 251 plots of 1 ha, the presence of L. pulmonaria, tree species, and diameter at breast height were recorded. An analysis of variance showed that neither historical stand‐level disturbances nor current grazing reduced the proportion of colonized trees. Spatial analysis at the tree level revealed a patchy distribution of colonized trees, suggesting L. pulmonaria colonization from nearby sources. Spatial analysis at plot level even showed a positive spatial association of L. pulmonaria with historic disturbances. We conclude that the presence of L. pulmonaria may provide information about conservation value of a landscape, but not necessarily at a forest stand scale. Although indicator species, such as L. pulmonaria, may be an efficient means to assess the conservation value of a forest, spatially and temporally explicit knowledge of the species' life history characteristics is indispensable in order to prevent possible misinterpretation of ecological processes that the indicator aims to unravel.

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

“…Remnant trees colonized by L. pulmonaria may act as a source of propagules to inoculate the surrounding younger trees, but there had been little time for the lichen to establish and grow on these trees. This agreed with previous studies that assessed the ability of L. pulmonaria to persist on residual trees and to reestablish in areas disturbed by selective cutting (Kalwij et al 2005;Wagner et al 2006;Bolli et al 2008). The lichen cover showed an aggregated pattern and the dispersal of the species was not limited at this local scale, so this might be an effective dispersal process in a young unsaturated system.…”

“…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).…”

Canopy macrolichen distribution in a very wet oldgrowth forest landscape of the upper Fraser River watershed.

“…First, the presence and high abundance of L. pulmonaria across most of our research sites (wet or dry) proved not to be a sensitive indicator to site-specific conditions and lichen diversity (as suggested by Campbell and Fredeen (2004)). This result concurs with Kalwij et al (2005) that suggested that L.pulmonaria at the site level is not sensitive to landscape disturbances, but could be a useful indicator of lichen diversity and disturbance frequencies when comparing among regional landscapes.…”

Threatened forest lichen Lobaria pulmonaria - its past, present and future in Estonia

“…Lobaria pulmonaria often grows in a large variety of semi-natural biotopes with scattered old trees, for instance, such as old parklands, pasture-woodlands and wooded meadows (e.g. Hallingbäck & Martinsson, 1987;Rose, 1992;Wolseley & James, 2000;Kalwij et al, 2005;Carlsson & Nilsson, 2009;Jüriado & Liira, 2009). In semi-natural biotopes, optimized and adequate management of the habitat is crucial for the maintenance of endangered species, as both the cessation of traditional land use and too intensive management activities may threaten sensitive lichen species (Rose, 1992;.…”