CLASSIFICATION OF SEMI-NATURAL GRASSLANDS IN NORTH-EASTERN BULGARIA

This study presents the syntaxonomic diversity of the semi-natural grasslands in NorthEastern Bulgaria following the principles of the Ziirich-Montpellier School. A total number of 172 releves, collected during 2002-2004, is used. TWINSPAN clustering is applied for determination vegetation types. The diagnostic species groups for the associations and subassociations are created by Cocktail method using the phi-coefficient with values above 0.3 within the JUICE software. As a result class Fesluco-Brometea is established with the alliances Festucion valesiacae, Pimpinello-Thymion and Chrysopogoni-Danthonion. The originally described Botriochloetum ischaemi Pop 1977 association is considered as typical on the subassociation level and a part of our releves are referred to it. Following the nomenclature rules we determined the subassotiation typicum. One new subassociation named Thymefosum pannonici of more xerophytic character, as compared to typical one, and well represented by differential species is established. The geographical distribution of Agropyro-Thymetum zygoidi and Agrostideto-Chrysopogonetum grylli associations is extended to the territory of Bulgaria. Class Molinio-Arrhenalherefea is represented by Cynosurion alliance and Festuco-Agrostidetum association is established by its probably most eastern area of distribution.