Abstract
The calcareous pine forests have one of the highest species diversity among the forest communities in northern Europe. We analysed their classification structure and the relationship with principal environmental variables on Gotland Island, South East Sweden. There were 14 species recorded in the tree layer, 60 species in the shrub layer, including 18 species of tree saplings, 273 species in the field layer and 80 species in the moss layer. The former classifications of the Gotland’s calcareous pine forests are conducted too coarsely or without statistical justification of established community types. In the current study the stands were classified into four community types, 1) Arctostaphylos uva-ursi-Tortella tortuosa type, 2) Brachypodium sylvaticum-Rhytidiadelphus triquetrus type, 3) Carex montana-Scleropodium purum type and, 4) Geranium sanguineum-Scleropodium purum type. All these community types have significantly different species content and they are mutually distinct also by numerous considered environmental variables. The species variation in the shrub, field and moss layers was related primarily with three rather strongly correlated variables: tree layer height, abundance of Picea abies (L.) H.Karst. and soil humus horizon depth. Soils were mainly the Sceletic Regosols or Calcaric Gleyic Regosols, but also Rendzic Leptosols.