Adaptation strategies of Heracleum sosnowskyi in Ukrainian Polissia

Abstract

Heracleum sosnowskyi is an invasive transformer species dangerous for biodiversity and human health. The materials for this study were the standard geobotanical descriptions made on the territory of Ukrainian Polissia in the period from 2004 to 2022. The relevés were classified using the Braun-Blanquet methods and used for synphytoindication evaluation of the environmental factors, rating ecofactors, estimated based on the ecological scales of the species that form a phytocoenosis. Heracleum sosnowskyi was observed to occur in plant communities belonging to 13 classes, 16 orders, 21 alliances, and 29 associations. According to the synphytoindication, it most often grew in mesophyte, hemihydrocontrasthophobic (moderately moistened habitats that are sporadically moistened), subacidophilic, semieutrophic, acarbonataphilic, nitrophilic, hemiaerophobic (moderately aerated habitats), submicrothermal (habitats that receives 20–30 kc/sm2), subombrophytic, hemioceanic, subcryophytic (habitats with the average temperature of the coldest month of the year is approximately –8), semi-illuminated, euhemerobic (habitats that have been altered or created by humans and are under anthropogenic influence) habitats. The competitive advantages of Sosnowsky's hogweed over the native species are the combination of the ability to change r and K strategies, depending on the environmental conditions, with the production of a large number of seeds that are dispersed from a tall peduncle, maintaining a significant germination rate for several years, and allelopathy and efficient assimilation of nitrogen compounds, which helps it to increase the size of the shoot. Ruderal and natural grass ecosystems are the most vulnerable to the penetration of H. sosnowskyi in the early stages of autogenic succession (value of natural dynamic was 3.0–4.0 points). The highest projective cover and the density of its population were observed in the nitrified forest edges of associations Elytrigio repentis-Aegopodietum podagrariae var. Heracleum sosnowskyi (value of natural dynamic was 4.0–7.0 points). Forest ecosystems with multi-tiered vegetation (value of natural dynamic was above 9.5 points) and meadows with thorough sod (value of natural dynamic was above 4.8 points) were less vulnerable to invasions. At the same time, disruptions of the completeness of the tree stand or the integrity of sod created additional opportunities for the species to invade the territory. Once penetrating into natural or ruderal ecosystems, H. sosnowskyi most often transforms their autotrophic blocks into a variant of association Agropyretum repentis var. Heracleum sosnowskyi of class Artemisietea vulgaris, which is a more favorable phytocenosis for its intensive reproduction and spread. The results of the study can be used to prevent the spread of H. sosnowskyi.