Silicicolous lichen communities of the Ukrainian Crystalline Shield

QuestionsHow many different silicicolous lichen syntaxa occur on the Ukrainian Crystalline Shield and what ecological factors are influencing their distribution? LocationUkrainian Crystalline Shield, Steppe and Forest-Steppe zones, Ukraine. MethodsThe field research was performed during 2013-2020. Analysis was done with the JUICE software using agglomerative hierarchical cluster analysis in the integrated PC-Ord with data transformation, pseudospecies cut levels 0-5-25, distance measure - Jaccard, group linkage - Ward's method. For the ordination of the plots we used detrended correspondence analysis (DCA) and non-metric multidimensional scaling (NMDS) with the "envfit" function, implemented in the R package vegan. As environmental variables we used mean indicator values obtained for each species from the ITALIC database. A generalized synoptic table, which combined both our own and literature data, was clustered using Euclidean distances and the Ward error sum of squares hierarchical clustering method with Ward's criterion. ResultsSeven clusters were obtained after JUICE analysis based on 197 releves of lichen communities that included 119 lichen species. The main axis in both DCA and NMDS ordination is similar to the vector of substrate pH value. Communities on overhanging surfaces are acidophilous. Communities of water tracks are moderately basophilous to basophilous. Other communities included releves on different granite characterized as mainly neutrophilous. Lichen communities on siliceous rocks of the Ukrainian Crystalline Shield are assigned to the classes Rhizocarpetea geographici, Leprarietea chlorinae, and Collematetea cristati. Two new alliances (Aspicilion intermutantis and Staurothelion frustulentae), four new associations and three subassociation are described. ConclusionSilicicolous lichen communities of the Ukrainian Crystalline Shield differ from the known units of Central Europe by species composition, where lichens with arid ecology are present. Their local distribution depends mainly on a combination of substrate pH, degree of eutrophication, protection from rain, and substrate moisture.