Terricolous lichen communities in Thero-Airion dry grasslands of the Po Plain (Northern Italy): syntaxonomy, ecology and conservation value

Terricolous lichen vegetation has been partially studied in Italy so far, particularly in the Po Plain. Here, pioneer acidic Thero-Airion dry grasslands host rich terricolous lichen communities which often include lichen species of conservation concern. Overall, 288 phytosociological releves were carried out with the Braun-Blanquet method using standard plots of 30 cm x 30 cm in lichen-rich stands within Thero-Airion dry grasslands located in 16 localities of the western Po Plain, an area with continental climate. Releves were manually sorted and species composition was analyzed through Principal Component Analysis (PCA) and non-parametric MANOVA. Biological, ecological, chorological and rarity spectra were computed and analyzed with Kruskal-Wallis tests to assess differences among the communities. Nine lichen communities were recognized. One community dominated by Cladonia pulvinata referred to the Pycnothelio-Cladonietum cervicornis. Three communities referred to the Cladonietum foliaceae are dominated respectively by C. foliacea, C. furcata and C. rangiformis. Three communities referred to the Cladonietum rei are dominated respectively by C. rei, C. polycarpoides and C. coccifera. Two communities dominated respectively by C. peziziformis and C. cariosa are referred to an undescribed association, temporarily attributed to the Cladonion rei. All communities significantly differ in the mean ecological indicator values - soil pH, light, aridity, eutrophication, poleotolerance. The communities Pycnothelio-Cladonietum cervicornis, Cladonietum foliaceae (C. foliacea facies) and the C. peziziformis-C. cariosa community are pioneer communities. The Cladonietum rei (C. rei facies) and the Cladonietum foliaceae (C. rangiformis facies) are the more mature communities, respectively in disturbed and undisturbed sites. This study shows that terricolous lichen communities represent an important component of biodiversity in Thero-Airion dry grasslands, due to their diversification in different syntaxa and, in some cases, to their role as microhabitats for lichen species of conservation concern. Thus, our study contributes to the knowledge on Thero-Airion dry grasslands, which is a key component in the choice of management and conservation strategies.