67 PHYTOLOGIA BALCANICA 17 (1): 67 –78, Sofia, 2011 Alliance Arrhenatherion elatioris in West Bulgaria Nikolay Velev 1 , Iva Apostolova 1 & Zuzana Rozbrojová 2, 3 1 Department of Plant and Fungal Diversity and Resources, Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Acad. Georgi Bonchev St., bl. 23, 1113 Sofia, Bulgaria, e-mail: nvelev@bio.bas.bg (corresponding author); iva@bio.bas.bg 2 Institute of Botany, Czech Academy of Sciences, Lidická 25/27, CZ-60200 Brno, Czech Republic 3 Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic, e-mail: zuzkaroz@sci.muni.cz Received: February 16, 2011 ▷ Accepted: March 21, 2011 Abstract. Vegetation relating to the alliance Arrhenatherion elatioris has been studied in the central part of West Bulgaria. Classification and ordination of vegetation were performed. As a result of the analyses, four associations have been identified: Ranunculo repentis-Alopecuretum pratensis, Tanaceto vulgaris-Arrhenatheretum elatioris, Pastinaco sativae-Arrhenatheretum elatioris and Ranunculo bulbosi-Arrhenatheretum elatioris. In ass. Ranunculo repentis-Alopecuretum pratensis, two distinctive subgroups have been observed, differing in humidity of their substrate. The more humid one is the typical variation of the association, while the drier one is described as var. Eryngium campestre. The mode of vegetation use within the framework of the four associations is commented on. Key words: classification, mesic grasslands, ordination, syntaxonomy, vegetation Introduction Mesophyllous vegetation of the class Molinio-Arrhena- theretea is very poorly studied in Bulgaria. The alli- ance Arrhenatherion was reported for the first time in Meshinev & al. (2005) and further commented in more details by Velev & al. (2010). All syntaxa pub- lished according to Braun-Blanquet approach for the country are summarized by Tzonev & al. (2009). On- ly one association and one plant community have been referred to alliance Arrhenatherion. Association Arrhenatheretum elatioris Br.-Bl. 1915 is reported for Sofia region (West Bulgaria), while the geographical variant of the association (Central Balkan Geographic Variant) is described from the Rhodopes (Apostolova & al. 2007). A plant community of the type Poa prate- nsis-Dactylis glomerata (Pavlov & al. 2006) is men- tioned for the alliance, described from the northern slopes of the Central Balkan Range. The purpose of the present study is to identify the syntaxonomic diversity of the alliance Arrhenatherion elatioris in the central part of West Bulgaria. Material and methods The study area lies in West Bulgaria, stretching over three administrative districts of the country: the re- gion of Sofia City, Sofia district and Pernik district (Fig. 1). They cover an area of 10796 km 2 , account- ing approximately for one-tenth of the territory of the country. The physical and geographical characteris- tics of the studied region are presented by Velev & al. (2010). A total of 539 vegetation plots were sampled within the framework of three vegetation seasons (in the period 2007–2009). The plots have been laid out so as to cover uniformly the entire study area. We used a subset of 298 relevés which were previously classi-