Environmental and historical effects on lichen diversity in managed and unmanaged wooded meadows

Question Which environmental and historical variables affect epiphytic lichen diversity in managed and unmanaged wooded meadows? Location The island of Gotland located in the Baltic Sea east of the Swedish mainland. Methods We examined total epiphytic lichen diversity (crustose, foliose and fruticose species) on 1148 trees in eight grazed, eight traditionally managed (mowing, hay gathering and pollarding) and seven unmanaged wooded meadows. In addition to management, data on site location, habitat structure, history and adjacent habitat were analysed. Results Lichen species richness increased with wooded meadow area and was greater within managed sites than in unmanaged meadows. Historic crown cover (ca. 1930) also influenced present-day lichen richness. Geographic location, distance to sea, wooded meadow area and average tree circumference were important determinants of lichen species composition. Tree circumference was the strongest overall predictor of the number of species on individual trees. However, tree circumference interacted with management regime, whereby cessation of management appeared to reduce species richness most on large trees. Traditionally managed sites, on average, supported the greatest richness of red-listed species. Conclusions Management regime, wooded meadow area and canopy cover were the main drivers of lichen species richness, while geographic location, wooded meadow area, distance to sea and average tree circumference were important determinants of species composition.