Second, because their correlation (scores-cost) is positive, trees in a score-based selection have economic values higher than average, an effect of diameter being part of the score (see also Babcock et al. 1997). Although retention approaches in forestry were introduced only a few decades ago (Gustafsson et al. 2012), a large number of ecological studies have been performed in relation to this practice (Lindenmayer et al. 2012). Reviews of results have also been made, indicating overall positive effects to biodiversity (Gustafsson et al., 2010, Rosenvald
and Lõhmus, 2008 and Vanderwel et al., 2007). Still, the knowledge on links between specific tree properties and tree-associated plants see more and animals are scarce for retention trees. Our study shows that for aspen, black-colored bark and slow tree growth as well as other features related to tree form and bark texture, are important for the epiphytic lichen flora. Stem shape and bark properties have also been found to be important in other studies on lichen epiphytes in different environments, although their relative importance vary (e.g. Fritz et al., 2009 and Ranius et al., 2008). Mechanisms behind the influence of the tree properties seem related to factors
like bark chemistry and water-holding capacity (Ellis 2011). Balmford and Gaston (1999) suggest that the savings in the amount of land to protect that comes from a more efficient, complementarity-based NSC 683864 site
selection is commonly at least 5%. In our score-based selection, with representation of all species or all species of conservation concern as the conservation goal, 3.5 fewer trees (11.7% of all trees) were needed, supporting their suggestion. Making a selection of the cheapest trees, by prioritizing small diameters, led to more trees, but with lower economic value. Thus, this type of selection, which has been demonstrated also in other studies (see e.g. (Juutinen et al., 2004, Moore et al., 2004 and Perhans et al., 2008) could be an alternative strategy. But, it is opposite to current, field-based knowledge from biologists and researchers, Tyrosine-protein kinase BLK who usually view large aspen trees as having special value to epiphytic lichens (e.g. Nitare, 2000 and Gärdenfors, 2010). Importance of large-diameter trees for lichens has been found also for other tree species (e.g. Aragon et al., 2010, Johansson et al., 2007 and Thor et al., 2010). Thus, we caution against applying this strategy until more studies have been made on the link between aspen diameter and the epiphytic lichen flora. Occupancy or representation on the clearcut is a baseline starting point. However, the relationship between occupancy and long-term viability in the landscape is the ultimate response variable or target for conservation, but beyond what could be studied with this dataset.