Cryptogamic communities on flatroofs in the city of Debrecen (East Hungary)

Cryptogams of ten urban flatroofs, contrasting in their age and size, were studied between 2016 and 2018. Siliceous (bituminous felt, gravel, brick) and calcareous (concrete) substrata occurred at each site. Microclimate (T, RH) at two sites of contrasting shading was monitored from September 2016 to January 2017. Biomass of two differently aged, exposed flatroofs was sampled in October 2018. Taxa of Cladonia and Xanthoparmelia have been identified by spot tests and HPTLC. A total of 61 taxa (25 bryophytes, 36 lichens), mostly widespread synanthropic species, have been detected with an explicit difference of species composition between shaded and exposed sites. Floristically interesting species included acidophilous bryophytes (Hedwigia ciliata, Racomitrium canescens) and lichens (Xanthoparmelia conspersa, Stereocaulon tomentosum) of montane character. The most widespread lichen is Cladonia rei which accounted for a significant part of the biomass at selected sites. Species-area curves for bryophytes at exposed sites have become saturated at 100-150 m(2). In contrast, saturation of lichen diversity has not been reached even at the largest sites. Flatroofs with traditional roofing techniques can harbour relatively diverse microhabitats and species-rich synanthropic vegetation. It is urgent to study these sites before renovation with modern roofing techniques eliminates them. Diversification of urban surroundings is possible in the future via application of various substrats in renovated and newly constructed roofs.

Automated summary

Between 2016 and 2018, the cryptogams of ten urban flatroofs with different age and size were studied. Siliceous and calcareous substrata were found at each site. The microclimate at two shaded sites was monitored from September 2016 to January 2017. In October 2018, the biomass of two different aged flatroofs was sampled. Cladonia and Xanthoparmelia taxa were identified. A total of 61 taxa were detected with a difference in species composition between shaded and exposed sites. The diversity of lichen has not reached saturation even at the largest sites. Flatroofs with traditional roofing techniques can support diverse microhabitats and species-rich synanthropic vegetation. It is important to study these sites before renovation with modern roofing techniques eliminates them. Diversification of urban surroundings is possible in the future through the use of various substrates in renovated and newly constructed roofs.