Pine forest lichens under eutrophication generated by a great cormorant colony

Lichen community changes were investigated on trees within a colony of great cormorants (Phalacrocorax carbo sinensis) established in a pine forest on the Curonian Spit, western Lithuania. The impact of birds on the forest has altered the number and characteristics of substrata available to lichens. The lowest number of lichen species and occurrences was registered on trees in the most active part of the colony with the highest nest density. Lichen community patterns were most strongly related to P and Ca content in substrata and pH values. Some acidophytic species showed negative correlations, both with long-term and short-term ornithogenic influence. However, three acidophytes (Chaenotheca ferruginea, Lepraria incana, Coenogonium pineti) demonstrated an affinity for the transitional zone and recently occupied trees, and furthermore, C. pineti apparently reacted positively to a short-term ornithogenic influence but negatively to a long-term one. These three lichens, along with algae, were the main, and often the only, components of epiphytic communities on trees at the edge of the colony and apparently indicated the crucial point of the acidophytic community under the increasing load of nutrients. All nitrophytic species showed an affinity for a long-term bird influence and reacted negatively to a short-term influence. Only free-living algae (predominating species Desmococcus olivaceus) showed a clear affinity for trees occupied by bird nests. Hypogymnia physodes was found to be an indicator for early environmental changes following eutrophication. The study also showed that high concentrations of P did not have a mitigating effect on the detrimental impact brought about by increases in N and pH levels, but was possibly equally detrimental to acidophytic lichens.