Effects of the holm-oak canopy on the distribution of terricolous bryophytes and lichens

The effects of holm-oak canopy (Quercus ilex ssp. ballota) onterricolous bryophytes and lichen were studied in the central part of
the Spanish Mediterranean region. Three habitats were distinguised:
understorey, crown border and open grassland. In all cases, the
understorey is floristically poor compared with open grassland. In the
N-exposed stands species richness is more homogenous between canopy
border and open grassland, while in-S exposed ones differences among
habitats are more pronounced. Cladonia rangiformis, C foliacea, C
cervicornis and Cetraria aculeata have higher presence and cover values
in all situations, and the bryophytes Hypnum cupressiforme and
Pleurochaete squarrosa are the main species. Most of the acrocarpic
mosses and fruticose lichens grow on the canopy border or open
grassland, while pleurocarpic mosses and foliose lichen with
cyanobacteria are most frequent under N-exposed canopies. The holm-oak
crown causes variations in insolation, rain distribution, temperature
and wind, and strongly influences the distribution of lichens and
bryophytes.