Distribution of Sosnowsky’s Hogweed (Heracleum sosnowskyi Manden.) at the Southern Border of Its Secondary Range in European Russia

This paper examines the distribution of Sosnowsky’s hogweed (Heracleum sosnowskyi) at the southern border of its secondary range (Kursk oblast, European Russia). Sosnowsky’s hogweed is widespread mostly in the western part of the region in areas where it was cultivated in fields in the second half of the 20th century. Analysis of the Heracleum sosnowskyi occurrence in anthropogenic and natural ecosystems of the region makes it possible to identify distribution patterns typical of invasive species at the initial stages of their secondary range formation: (1) most of the H. sosnowskyi foci are located in anthropogenic and seminatural habitats; (2) medium-sized (from 100 m2 to 1 ha) foci predominate; and (3) the majority of the foci are registered in areas located along roads. Sosnowsky’s hogweed intensely spreads in human settlements, especially in those affected by clearly manifested depopulation processes. In natural and seminatural habitats, the majority of foci are located on shores of water bodies. In forests, Sosnowsky’s hogweed occurs mainly at the edges in small groups of vegetative rosettes, except for areas affected by strong anthropogenic impacts, where multiple foci with generative shoots are formed. At present, H. sosnowskyi is not registered on arable lands owing to their intense cultivation in the region. Plant communities involving Sosnowsky’s hogweed are represented in Kursk oblast by four syntaxa: (1) association Urtico dioicae–Heracleetum sosnowskyi; (2) association Rudbeckio laciniatae–Solidaginetum canadensis, variant Heracleum sosnowskyi; (3) association Chelidonio–Aceretum negundi, variant Heracleum sosnowskyi; and (4) derivative community Heracleum sosnowskyi [Agropyretalia intermedio–repentis].