The ericaceous dwarf shrublands above the Northern Apennine timberline (Italy)
Ferrari, C.; Piccoli, F.
Ericaceous dwarf shrublands which are settled above the timberline on a long stretch of the Northern Apennines were studied with the Braun-Blanquet approach. Phytosociological data were numerically treated through the following steps: 1) species ranking by a variance criterion; 2) classification of relevés and species based on the reduced species set; 3) characterization of the resulting types by analysis of concentration. The following three main vegetation types were recognized: a) Empetro-Vaccinietum gaultherioidis subass. juncetosum trifidi, which is the shrubland corresponding to the sites with less suboceanic climate; b) Rhododendretum ferruginei, which is a very rare, sometimes fragmentary community settled on small areas, and c) Hyperico richeri-Vaccinietum gaultherioidis, which corresponds to the sites with suboceanic climate. The first two have a high similarity with the corresponding vegetation types from the Alps and are their most southern known examples in Italy. The third type is typical of the Northern Apennines and has only fragmentary examples southwards on this chain. On rare and small areas two impoverished plant communities which are related to the Empetrum-Vaccinietum were also described: Thymus alpigenus/Vaccinium gaultherioides community, on summit windy sites with rocky soils, and Polygonatum verticillatum/Vaccinium gaultherioides community on summit sites on low mountains towards the north-western end of the Northern Apennine dwarf shrublands. The summit dwarf shrublands of the Northern Apennines are dominated by boreal and south-european orophytes, to whom arctic-alpine taxa are added into the Empetro-Vaccinietum gaultherioidis subass. juncetosum trifidi. At high syntaxonomical levels the Empetro-Vaccinietum gaultherioidis subass. juncetosum trifidi and the related impoverished plant communities are to be included in the alliance Loiseleurio-Vaccinion. The Rhododendretum ferruginei and the Hyperico richeri-Vaccinietum gaultherioidis belong to the Rhododendro-Vaccinion. Such dwarf shrublands are chiefly related to differences in the snow cover duration and height. All the plant communities stress the phytogeographic connection among the Northern Apennine summit vegetation and the subalpine vegetation belt of the Alps.