Communities with Heracleum sosnowskyi Manden. in the Kursk Region

Classification of communities with Heracleum sosnovskyi in the Kursk Region (Table 1), based on 43 relevés, made by the author in 2014–2020 in some locations mainly in the western part of the study area (Fig. 1), is carried out according to Braun-Blanquet approach. The data are treated by IBIS 7.2 software package (Zverev, 2007). The names of the higher syntaxa follow to «Vegetation of Europe…» (Mucina et al., 2016). Synoptic tables include only species with constancy above I. Soil moisture, reaction, richness in mineral nitrogen, light, temperature and continentality are assessed using mean H. Ellenberg ecological indicator values (Ellenberg et al. 1992), hemeroby — with these of N. G. Ilminskikh ecological 9-point scale (Ilminskikh, 1993). Significant differences between pairs of syntaxa for each environmental factor are determined by the Mann-Whitney U-test in the PAST package (Hammer et al. 2001). 3 associations, 2 variants and 1 derivative community of 3 classes of vegetation are established. Ass. Chelidonio–Aceretum negundi L. Ishbirdina in L. Ishbirdina et al. 1989, var. Heracleum sosnowskyi (Table 2, Fig. 2). The association belongs to alliance Chelidonio–Acerion negundi L. Ishbirdina et A. Ishbirdin 1989, order Chelidonio–Robinietalia pseudoacaciae Jurco ex Hadač et Sofron 1980, class Robinietea Jurco ex Hadač et Sofron 1980. DS of the association are Acer negundo, Chelidonium majus, that of the variant is Heracleum sosnowskyi. Communities most often have three layers. The tree layer is dominated by Acer negundo with 7–20 m heigh and 50–90 % canopy density. The shrub layer (1–3 m, 1–50 %) is dominated by Acer negundo undergrowth, sometimes there are Padus avium, Populus alba, Prunus domestica, Sambucus nigra, S. racemosa, Ulmus glabra. The herb-d­warf shrub layer (height – 70–150 cm, plant cover – 50–100 %) is dominated by Heracleum sosnowskyi, mainly by its vegetative shoots. Generative shoots are found mainly in the most sunlit sites. There are 68 species in the association with 7–21 species per sample plot. The communities formed as a result of H. sosnowskyi penetration into phytocenoses of the var. typica ass. Chelidonio–Aceretum negundi are common in wastelands, along roads and banks of reservoirs, near abandoned houses in villages. There are slight differences in habitats of variants Heracleum sosnowskyi and typica (Fig. 3, Table 4): communities of the first one inhabit wetter soils, while these of the var. typica have the higher levels of temperature, continentality and hemerobiality, that is why there is a lot annuals and biennials, many of which are continental thermophilic species and belong to eu- and polyhemerobes (Lactuca serriola, Atriplex tatarica, Arctium tomentosumи др.). H. sosnowskyi exists even in heavily shaded areas. The species composition of communities of the var. Heracleum sosnowskyi is quite stable which is facilitated by the flow of seeds from surroundings and the capacity of germination of those seeds that did not germinate in the first year, as well as the ability of specimens to exist in a vegetative state for a long time under unfavorable conditions (Vinogradova et al., 2010; Panasenko, 2017). Ass. Urtico dioicae–Heracleetum sosnowskyi Panasenko et al. 2014 (Table. 5, rel. 1–17, Fig. 4). The association belongs to alliance Aegopodion podagrariae Tx. 1967 nom. conserv. propos., order Circaeo lutetianae–Stachyetalia sylvaticae Passarge 1967 nom. conserv. propos., class Epilobietea angustifolii Tx. et Preising ex von Rochow 1951. DS: Heracleum sosnowskyi, Urtica dioica. The total plant cover is 80–100 %. Communities have three sub-levels: the upper one (1.0–1.5 m) is of Heracleum sosnowskyi generative shoots; the mid one (1–1.5 m) is of its leaves; the lower one is of herbs Anthriscus sylvestris, Arctium tomentosum, Artemisia vulgaris, Ballota nigra, Cirsium arvense, Dactylis glomerata, Elytrigia repens, Galium aparine and Urtica dioica. There are 83 species in the association, with 9–29 species per sample plot. Such communities, formed as a result of Heracleum sosnowskyi invasion into phytocenoses of the class Epilobietea angustifolii, often occur in anthropogenic habitats. Derivative community Heracleum sosnowskyi [Agropyretalia intermedio–repentis] (Table. 5, rel. 18–25, Fig. 5). DS: Heracleum sosnowskyi. The total plant cover is 85–100 %. Communities have three sub-levels, just like in the previous syntaxon. However, in contrast to it, species of Artemisietea vulgaris Lohmeyer et al. in Tx. ex von Rochow 1951 prevail in the derivative community (Table. 6). Species of order Agropyretalia intermedio–repentis T. Müller et Görs 1969 are represented with high constancy. Such communities, formed as a result of Heracleum sosnowskyi invasion into phytocenoses of this order, occur along roads, in wastelands, on dry meadows. There are 68 species in the community coenoflora, with 7–30 species per sample plot. There are differences in habitats of this derivative community and the ass. Urtico dioicae–Heracleetum sosnowskyi (Fig. 6, Table 7). Communities of the association often inhabit wetter and eutrophic soils, while derivative ones are common in more sunlit and heated sites. Ass. Rudbeckio laciniatae–Solidaginetum canadensis Tüxen et Raabe ex Anioł-Kwiatkowska 1974, var. Heracleum sosnowskyi (Table. 5, rel. 26–31, Fig. 7). The association belongs to alliance ­Dauco-Melilotion Görs ex Rostański et Gutte 1971, order Onopordetalia acanthii Br.-Bl. et Tx. ex Klika et Hadač 1944, class Artemisietea vulgaris. DS of the association is Solidago сanadensis, this of the variant is Heracleum sosnowskyi. Both are dominating species. The total plant cover is 100 %. Phytocenoses have three sub-levels: the upper one (up to 3 m high) is of H. sosnowskyi generative shoots; the mid one (1.0–1.5 m) is of its leaves (sometimes quite numerous) and of Solidago сanadensis; the lower one (up to 0.5 m high) is of Heracleum sosnowskyi seedlings, as well as of Achillea millefolium, Carex hirta, Equisetum arvense and Poa angustifolia with lower cover. There are 48 species in the association, with 12–18 species per sample plot. Such communities common in the northwestern part of the Kursk region occur in wastelands, along roads and banks of reservoirs. They appeared as a result of Heracleum sosnowskyi penetration into phytocenoses of the ass. Rudbeckio laciniatae–Solidaginetum canadensis (Fig. 8), as well as with concurrent spread of both Heracleum sosnowskyi and Solidago сanadensis on the territory (Fig. 9). In spite of significant differences in soil moisture and temperature, in general, habitats of variants Solidago сanadensis and Heracleum sosnowskyi of the ass. Rudbeckio laciniatae–Solidaginetum canadensis are rather similar (Fig. 10, Table 8). There are fewer xeromesophytes of the order Onopordetalia acanthii and more species of the class Epilobietea angustifolii in the species composition of the var. Heracleum sosnowskyi (Table 9).