Influence of tree substrates on the diversity of epiphytic lichens: comparison between Tilia platyphyllos and Quercus ilex (Central Italy)

A comparison between lime (Tilia platyphyllos) and holly oak (Quercus ilex) as substrate trees for epiphytic lichens was carried out in Siena (central Italy). The purpose of this study was to investigate the influence of these phorophytes on the diversity of epiphytic lichens, at a similar climatic regime and at the same air pollution status. The diversity values measured on Tilia were on the average 1.5 times higher than those on Quercus. No difference between the two tree species appeared for bark pH and bark concentrations of NO3 -, SO4 2-, NH4 +, Cu, and Pb. Bark concentrations of Mn were higher for Quercus. The water-holding capacity of the bark of Tilia was higher than that of Quercus. The amount of incident light radiation was similar for the two trees in summer, when both species have leaves, but was higher on deciduous lime in winter, when only the evergreen Q. ilex has leaves. Influx light in winter is the most important factor for determining differences in the biodiversity of epiphytic lichens on Tilia and Q. ilex.