Effects of stand-level disturbances on the spatial distribution of a lichen indicator. [Erratum: 2006 Apr., v. 16, no. 2, p. 838.]

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.