R. Carballal

Lichen colonization of coastal churches in Galicia: biodeterioration implications

Lichen colonization of four granite churches situated in coastal areas in Galicia (NW Spain) were studied with the aim of understanding relationships among lichens, salts and biodeterioration. The results obtained here were compared with those from previous studies on lichen colonization of non-coastal churches. As a result of the field survey undertaken in granite churches, it can be concluded that there is a group of characteristic species on granite monuments whatever the environmental conditions are. Besides this group of characteristic species, a large number of species were identified on each coastal church that brought some important data to the relationship between salts weathering and the protective action of lichens.

Rapid biological colonization of a granitic building by lichens

Abstract The Galician Centre of Contemporary Art (Santiago de Compostela, Spain) is a large, modern building finished with a granitic cladding. Completed in September 1993, it is already showing signs of deterioration, including biological colonization and intense blackening of exterior surfaces, and the breaking off of cladding. In this work we investigated the causes of this premature deterioration. Biological colonization was most intense on the lower areas of shaded walls, the most abundant organisms being the lichens Trapelia coarctata and T. involuta . The blackening was chiefly due to the build up of microorganisms or their remains (no elements indicative of atmospheric pollution were detected). Both the cladding and granite from the source quarry showed signs of severe weathering (fissuration, high porosity, the presence of kaolinite) and had high capillarity, rapidly absorbing large amounts of water and releasing it only slowly. Because of this and the wet climate in Santiago the cladding was almost permanently damp, which, together with its weathered condition, made it highly bioreceptive and, at the same time, reduced its mechanical resistance, making it susceptible to breakage.

Colonization by lichens of granite dolmens in Galicia (NW Spain)

Abstract We studied colonization by linchens of five granite dolmens in Galicia (NW Spain). A total of 60 species, 3 subspecies and 2 varities (some cited for the first time in Galicia) were identified, and the positions in which they occurred on the dolmens were mapped. The factors most strongly influencing colony initiation and position were degree of exposure to rain, insolation, substrate verticality/horizontality, humidity and location (on the inside or outside of the chamber). We also evaluated microscopic-level effects of colonization by five species of lichen Xanthoria parietina, Aspicilia cinera, Diploschistes scruposus, Pertusaria coccodes and Ochrolechia parella ) in samples taken from nearby outcrops of the same granite as the dolmens. Hyphae were observed to penetrate almost exclusively through intermineral voids, except in the case of micas which were penetrated between layers. The only minerological effect observed was degradation of micas to mica-aluminium hydroxy vermicultie intergrades.

Caloplaca peregrina (Teloschistaceae), a synonym of C. pellodella

Abstract Caloplaca peregrina Samp., a species described from Portugal in 1917, and only known from the type localities, is synonymized with Caloplaca pellodella (Nyl.) Hasse.