摘要：Lowland and mountainous areas of central Serbia differ in many aspects primarily regarding climatic,edaphic and chorographic characteristics which is common to other regions as well.Such condition strongly affects the status of overall vegetation,including the characteristics of weed (grass) plant communities.We investigated this phenomenon in the case of weed vegetation of small grain crops (wheat,barley,oats,rye).We found completely different weed phytocoenoses in lowland and mountainous regions characterized by specific floristic composition,and synmorphological synecologicical and phytogeographic traits,as well as syntaxonomic status.Two main weed associations were identified and described: 1.ass.Consolido-Polygonetum avicularae Kojić et al.,1973 (lowland variant;broad area around Kraljevo) and 2.ass.Galeopsi-Grassicetum campestrae Ajder 1996 (mountain variant;Mt.Rudnik plateau).Considerable differences were identified between those two weed communities in small grain crops regarding their floristic structure,composition of the biological spectrum (life-forms of the weed phytocoenoses in small grain crops in mountainous regions,compared to lowland regions,indicated a tendency of increased participation of hemicryptophytes and a decrease of geophytes),and phytogeographic characteristics (floristic elements of broad distribution Euroasian,Cosmopolitan,Sub-Euroasian - predominate in both communities but there is a tendency of their increase in the phytocoenosis of mountainous areas).Those differences consequently result in the fact that weed associations in small grains of lowland and mountainous regions are mutually distant regarding syntaxonomy.They belong to different vegetation alliances.The association Consolido-Polygonetum avicularae is part of the alliance Caucalion lappulae Tx.1950,while the other association Galeopsi-Brassicetum campestrae belongs to another alliance - Galeopsian speciosae-pubescentis Kojić 1972.
