19 - Studia Geobotanica. An international journal - Vol. 19 (2000)

CONTRIBUTION TO THE EPIPHYTIC LICHEN FLORA OF UMBRIA (C. ITALY). 47 species of epiphytic lichens are reported as additions to the poorly known lichen flora of Umbria. The ecology and distribution of selected species are discussed.

The vegetation-environment relationship in the inland saltmarshes of Siwa and Dakhla, two geographically distant oases of the Western Desert of Egypt, are described. Two data sets (25 species x 68 relevés for Siwa Oasis, 29 species x 89 relevés for Dakhla Oasis) were analysed by multivariate procedures. Two-way indicator species analysis (TWINSPAN) was used to classify the plani communities ofthe study areas, whereas detrended correspondence analysis (DCA) and detrended canonical correspondence analysis (DCCA) were used to examine the relationship between the vegetation and selected edaphic factors (soil reaction, electric conductivity, calcium carbonate, organic matter, moisture conteni and fine fractions. Twelve halophytic plani communities linked to two main habitats (wet-moist and dry-mesic) were identified. In the two oases the most common communities are those of Alhagi graecorum, Tamarix nilotica, Cressa eretica, Juncus rigidus and Phragmites australis. Communities of Cyperus laevigatus, Suaeda aegyptiaca, Suaeda vermiculata, Typha domingensis and Aeluropus lagopoides are recorded from Dakhla Oasis; Cladium mariscus and Arthrocnemum macrostachyum communities are recorded from Siwa Oasis. The most important edaphic factors affecting distribution and structure of these piant communities are salinity, moisture content and fine fractions; CaCO3 content seems to be more effective in the Dakhla Oasis.

Pollen cards of the taxa of the Genista radiata group [ G. radiata (L.) Scop. var. radiata, G. radiata var. sericopetala Buchegger, G. holopetala (Koch) Bald., G. hassertiana (Bald.) Buchegger] are presented. The acetolyzed pollen was observed by light and scanning electron microscope.

THE WOOD COENOSES OF COLLI SERICI (VICENZA, NE lTALY). The syntaxonomical, chorological and ecological features of the wood coenoses occurring in the hilly area of Colli Berici (Vicenza, North-Eastern Italy) are described. Three associations are recognized: the suboceanic Omithogalo pyrenaici-Carpinetum Marincek et al. 1983, Buglossoido-Ostryetum Gerdol et al. 1982 em. Poldini 1988, which prefers more marked thermic excursions, and the synanthropical Lamio orvalae-Sambucetum nigrae Poldini 1980. The first association includes two coenoses: the gorge woods, characterized by species of Tilio-Acerion Klika 1955 and Lamio Acerenion Marincek I 990, and the subass. caricetosum pilosae Marincek et al. 1983. The Buglossoido Ostryetum is subdivided into two subassociations: typicum and pistacietosum terebinthi Poldini 1988. The latter is characterized by the presence of taxa of Quercetea ilicis Sr.-Sl. 1947 and by a higher incidence of species belonging to the the Mediterranean s.l. chorological type; its differential species are proposed. The marginal presence of two further associations (Melampyro vulgati-Quercetum petraeae s.lat. Puncer et Zupancic 1979 em. Zupancic 1994 and Carici umbrosae-Quercetum petraeae Poldini 1982) is hypothesized.