Epiphytic Lichen

Occupancy and density of the epiphytic lichen L. pulmonaria were studied in the
mountains of Uholka–Shyrokyi Luh (Ukraine), which include the largest primeval beech
forest in Europe. The lichen occupancy was assessed on 314 plots laid out on a systematic
grid. Additional data on population density were collected from 483 trees growing both, on
and between these plots. The trees harbouring L. pulmonaria were distributed very sparsely
within Uholka–Shyrokyi Luh, and occupy nearly 10 % of the studied perimeter. The generalized
linear models showed that area of occupancy of L. pulmonaria was significantly
influenced by altitude and canopy cover, whereas the species’ density was explained by
habitat types and slope exposition. Population density is higher at the timberline than in the
interior forest or on lowland meadows. We found a bimodal altitudinal distribution of L.
pulmonaria, with maxima below and above 900 m a.s.l., where it prefers forest stands with
loose or scattered canopy. The preferred position of L. pulmonaria on host tree trunks depends
on stand density and allows the species to get the necessary level of insolation also in shaded
sites where it grows higher up on the trunk than in open stands. While L. pulmonaria occupied
trees with various diameters, juvenile individuals are more frequent on small trees, but mature
lichen individuals are predominantly found on trees of average or large sizes. Fertile individuals
require specific environmental conditions, which are available at intermediate altitudes,
related with sheltered light, and horizontal terraces on slopes with eastern exposition.
In general, the primeval beech forest of Uholka–Shyrokyi Luh harbours a high percentage of
juvenile thalli of L. pulmonaria, which lack vegetative propagules. Mature individuals have a low frequency of fruit bodies and reproduce mainly with vegetative diaspores. We interpret
this as an indication of a currently growing population of L. pulmonaria within the area. We
hypothesize that transboundary air pollution has decreased the lichens’ population frequency
and density and has altered the ratio of developmental stages in L. pulmonaria during earlier
decades.

The Uholka-Shyrokyi Luh area of the Carpathian Biosphere Reserve is considered
the largest and the most valuable primeval beech forest in Europe for biodiversity
conservation. To study the impact of different topographic and forest-stand variables on
epiphytic lichen diversity a total of 294 systematically distributed sampling plots were
surveyed and 198 epiphytic lichen species recorded in this forest landscape, which has an
uneven-aged structure. The obtained data were analysed using a non-metric multidimensional
ordination and a generalized linear model. The epiphytic lichen species density at
the plot level was mainly influenced by altitude and forest-stand variables. These variables
are related to both the light availability i.e. canopy closure, and the habitat diversity, i.e. the
developmental stage of the forest stands and the mean stem diameter. We found that lichen
species density on plots with a relatively open canopy was significantly higher than on
plots with a fairly loose or closed canopy structure. The late developmental stage of forest
stands, which is characterized by a large number of old trees with rough and creviced bark,
had a strong positive effect on lichen species density. In the Uholka-Shyrokyi Luh primeval
forest the mean stem diameter of beech trees significantly correlated with lichen
species density per plot. Similar trends in the species diversity of nationally red-listed
lichens were revealed. Epiphytic lichens with a high conservation value nationally and internationally were found to be rather abundant in the Uholka-Shyrokyi Luh area, which
shows its international importance for the conservation of forest-bound lichens.