The vegetation on railway embankments of the Kursk region
The present paper deals with the classification of the plant communities developed on the railway embankments in Kursk region. This type of vegetation is still poorly studied in Russia although some floristic information is available for various regions. Kursk region is located between 50°54''-52°26'' N and 34°05''-38°31'' E. Its area is 29 800 km2. Zonal vegetation is represented by broad-leaved forests on dark-gray forest soils and meadow steppes on chernozems. The vegetation of the railway embankments was being studied in Kursk region since 2003. Railway embankment sections were surveyed in the city of Kursk, the towns of Dmitriev, Lgov, Oboyan, Rylsk, Shchigry, and urban settlements of Konyshevka, Kshenskiy, Ponyri, Pristen. The upper parts of railway embankments, slopes and nearby sites, stations, and areas between roadbeds were studied. Classification according to Braun-Blanquet approach, with the use of “deductive method” (Kopeсký, Hejný, 1974), is based upon 120 relevés. The data were treated by software package IBIS 7.2 (Zverev, 2007). The names of the higher syntaxa are given according to “Vegetation of Europe.” (Mucina et al., 2016). Direct ordination of relevés by soil moisture and nitrogen content factors (scales after H. Ellenberg et al. (1992)) was conducted to distinguish ecological specificity of the communities on railway embankment and those outside railways. The vegetation of the urbanized territories under strong man impact in general and in particular around railway stations is highly diverse. The plant cover regularly destroyed by herbicides re-establishes in different ways depending on the distance from the stations. The mostly diverse are communities on the railway slopes where the late successional stages are present due to the poorer pressure, These communities were compared with the undestroyed ones occurring beyond railways (Arepieva, 2015). Syntaxonomy of railway embankment vegetation in Kursk region includes 3 classes, 4 orders, 4 alliances, 9 associations, 2 subassociations, 4 variants and 3 communities. The class Sisymbrietea Gutte et Hilbig 1975 is represented by 4 associations (Conyzo canadensis-Lactucetum serriolae Lohmeyer in Oberdorfer 1957, Kochietum densiflorae Gutte et Klotz 1985, Ivaetum xanthiifoliae Fijalkowski 1967, Ambrosietum artemisiifoliae Vialariu 1973) belonging to the alliance Atriplicion Passarge 1978 within the order Sisymbrietalia sophiae J. Tx. ex Görs 1966. In the ass. Ivaetum xanthiifoliae new var. Melilotus officinalis is distinguished that contains species of dry grasslands (Melilotus officinalis, Conyza canadensis, Medicago falcata, Poa compressa) and is characterized by the low occurrence of nitrophillous species (Urtica dioica, Poa annua, Sisym brium officinale, Sonchus oleraceus) that are common in communities beyond the railways. Ass. Ambrosietum artemisiifoliae is new for the Kursk region. Class Digitario sanguinalis-Eragrostietea minoris Mucina, Lososova et Silc in Mucina et al. 2016 is represented by ass. Eragrostio-Amaranthetum albi Morariu 1943 belonging to alliance (Salsolion ruthenicae Philippi ex Oberdorfer 1983) within the order Eragros-tietalia J. Tx. ex Poli 1966. Its stands are common on railway embankments. Class Artemisietea vulgaris Lohmeyer et al. ex von Rochow 1951 is represented by two orders. The order Onopordetalia acanthii Br.-Bl. et Tx. ex Klika et Hadač 1944 includes 3 associations (Berteroetum incanae Sissingh et Tideman ex Sissingh 1950, Melilotetum albi-officinalis Sissingh 1950, Dauco carotae-Picridetum hieracioidis Görs ex Seybold et Müller 1972) and a basal community within alliance Dauco-Melilotion Görs ex Rostanski et Gutte 1971. In the ass. Melilotetum albi-officinalis the var. Ambrosia artemisiifolia that is an initial succession stage with larger number of Sisymbrietea class species compare to the var. typica is described. The basal community Tanacetum vulgare contains many graminoids and perennial grasses. The order