Community structure of corticolous microalgae within a single forest stand: evaluating the effects of bark surface pH and tree species
Abstract
Community structure of corticolous macro-epiphytes, such as lichens and mosses, usually strongly correlates with bark characteristics related to the taxonomic identity of the host tree. However, the reasons for the occurrence of similar patterns of microalgal corticolous biofilms are unclear and have rarely been investigated.
In this study, we surveyed aerial phototrophic biofilms growing on the bark of Acer, Alnus, Fagus, Fraxinus and Picea trees in a single stand of a temperate forest. A flathead electrode was used to measure and evaluate the effect of bark surface pH on microalgal species richness and composition.
In total, 47 distinct morphotypes were found, chiefly consisting of various coccoid green algae belonging to Trebouxiophyceae and Chlorophyceae. In addition, members of the Bacillariophyceae, Eustigmatophyceae, Streptophyta, Trentepohliales, Xanthophyceae and Cyanobacteria were also found.
Bark pH and species richness of the samples were positively correlated; in the most acidic samples (from Picea and Alnus trees), only green algae occured. Aerial diatoms, Cyanobacteria, Xanthophyceae and Trentepohlia sp. were only found in the more basic samples.
The species composition was significantly structured by the separated effects of host tree species, the bark pH and the sampling season. The observed non-random differences in community structure of the biofilms among host tree species indicated possible effects of deterministic processes, such as species sorting of microalgae along the environmental gradients.