Changes in epiphytic bryophytes’ occurrence in centre of Wrocław (Poland) during 2013-2023 and question of their relationship with climate changes

Last decade is considered as warmer than previous ones. Epiphytic bryophytes are known as quickly reacting on microclimate changes. The question whether occurrence and spread of epiphytic bryophytes in cities is presently facilitated or limited due to warming was studied through a comparison of species diversity, frequency and abundance in 2013 and 2023 in 109 research plots situated in central part of the Wrocław city. In result an increase in the total number of inhabited trees and the total area covered with epiphytes was evidenced, especially on built-up areas and streets. Fourteen species have shown an upward trend while six – the opposite tendency. An increase in the richness of obligatory epiphytes was found (five, including three new for Wrocław) but no new thermophilic species appeared. Two of newly found epiphytes are considered as sensitive to the air pollution. So bryofloristical changes seem to result from the improvement of the air purity not warming. Improving air purity could caused, with high probability, also the expansion of resistant to pollution epiphytes: Hypnum cupressiforme Hedw., Dicranoweisia cirrata (Hedw.) Lindb. ex Milde and Orthotrichum diaphanum Schrad. ex Brid. But the potential effect of the increased temperatures and frost-free winter months, observed in Wrocław since 2019, on spread in the city of two thermophytic species, Orthotrichum pumilum Sw. ex anon and O. diaphanum, should be considered when explain these phenomena. The mixed impact of both processes seem to be probable. Parks and built-up areas differed in the intensity of species exchange of epiphytic bryophytes.