Abstract
The phytosociology and ecology of Heliosperma pusillum in freezing ravines of the Trnovski gozd plateau (Slovenia, NW Dinaric Mts) are discussed. The species thrive on shadowy, moist, cold and stable screes of boulders with long-lasting snow cover. The stands belonged to the association Drepanoclado uncinati-Heliospermetum pusilli (Salicion retusae, Arabidetalia caeruleae, Thlaspietea rotundifolii). Due to close proximity to the Julian Alps, the stands host a significant number of SE - Alpine and N-Illyrian species. Therefore, a new geographical variant Paederota lutea is described. Differential species for the geographical variant are Phyteuma scheuchzeri ssp. columnae, Valeriana saxatilis, Rhodothamnus chamaecistus, and Saxifraga cuneifolia. For less stable screes with smaller rocky particles a new subassociation salicetosum retusae is described, and the differential species for the subassociation are Salix retusa and Poa alpina. Stands of the association Drepanoclado-Heliospermetum var. geogr. Paederota lutea from the Trnovski gozd plateau are on the north-westernmost part of the distribution area of the Dinaric alliance Salicion retusae.