The influence of tree age and microhabitat quality on the occurrence of crustose lichens associated with old oaks

Abstract

Methods: Eight crustose lichen species were surveyed on 165 Quercus robur trees, 17-478 years old, at three study sites. The occurrence patterns of these species were examined at two spatial scales: among trees and within trees. Occurrence patterns within trees were examined in 10 cm × 10 cm plots at all four cardinal aspects at different heights from 0.5 to 4.5 m above the ground.Results: At the tree level, age-related factors were the most important predictors of species occurrence. All species were more frequent on trees > 100 years than on younger trees. At the plot level, the frequency of occurrence increased with increasing bark crevice depth. The frequencies of all study species decreased with increasing cover of bryophytes.Bryophytes were in turn more frequent in plots that were exposed to rainwater and showed a low evaporation rate. Patches most exposed to rainwater were directed upwards, and the lowest evaporation rates occurred on the northern side of the trunks.Conclusions: For many crustose lichens the association with old oak trees seems at least partly to depend on their preference for the deep bark crevices that only occur on old trees. Trees represent epiphyte habitat patches that differ in size due to within-tree variability in habitat quality, such as bark crevice depth and microclimate. This study shows that variability at a finer scale, within habitat patches, contribute to explain species occurrence patterns at habitat patch level.

Generation time estimated to be 25–30 years in Cliostomum corrugatum (Ach.) Fr.

“…Preliminary studies had shown a very low occurrence of C. corrugatum on trees with a circumference < 200 cm in agreement with later studies (Johansson et al 2009;Ranius et al 2008). The occurrence and the size of the largest C. corrugatum thalli with apothecia and the size of the largest apothecia were recorded.…”

Epiphyte metapopulation dynamics are explained by species traits, connectivity, and patch dynamics

“…1; Appendix A: Table A1). All species except Chaenotheca phaeocephala are mainly found on old oaks (Ranius et al 2008). This species occurs also on old deciduous trees of other species.…”

“…One example is epiphytic lichens, of which many depend on the characteristic coarse bark of old oaks (Thor and Arvidsson 1999). The frequency and occurrence of many of these species increase with tree age or with tree characteristics that are correlated with age (Ranius et al 2008, Johansson et al 2010. As the tree ages, the abiotic conditions and the substrate suitability changes, and tree age is therefore a suitable, relatively easily measured, niche proxy for epiphytes.…”

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

“…The colonization probability at this scale might not be simply correlated with tree diameter, because bark characteristics are an important factor linked to habitat quality during the successful lichen establishment. Tree size is a major determinant of lichen dynamics, which is mainly related to the availability of different microhabitats, including bark crevices, porosity, roughness, the time available for colonization, and the increased surface area made available with tree growth (Snail et al 2003;Ranius et al 2008;Belinchón et al 2009). Scheidegger & Werth (2009) summarized the most important factors affecting attachment, dispersal, and establishment of L. pulmonaria.…”