Abstract

Introduction.The class group of Robinietea Jurko ex Hadac et Sofron 1980 of low Sula basin is artificial planting and spontaneous forest stands of introduced tree species (Robinia pseudoacacia and Acer negundo) with nitrophilic grass stands mostly on the place of natural forests. The works related to the class according to the geography and syntaxonomical composition are monographs concerning vegetation cover of Kaniv Nature Reserve, the Valley of Horol River and “Kremenchuk Plavni” Regional Landscape Park. Despite this, the number of published descriptions are still insufficient for the definitive conclusions concerning the syntaxonomical structure of the class. Its syntaxonomy is insufficiently developed not only in the Forest Steppe of Ukraine, but even in the states of Central Europe, including some associations being provisional and still invalidated. Purpose. The goal of our research is to show the coenotic variety of planting and spontaneous conenoses of Robinietea class in the region and to create its primary classification scheme. Methods.We used 20 geobotanical descriptions which were performed and processed according to the methods of Braun-Blanquet school. Results.Plantings Robinia pseudoacacia are divided into two units and five associations according to edaphic and micro-climatic conditions. Drier ecotopes occupied the union grouping Balloto nigrae-Robinion Hadac et Sofron 1980. The most ruderalized grouping of Robinia on the warm slopes of clay fields is attributed to the association of Elytrigio repentis-Robinietum Smetana 2002; grouping on the sandy loam of upland terraces and high floodplain are attributed to the provisional association of Calamagrostio epigeioris-Robinietum ass. nova prov. Robinia groups in mesophilic conditions at the site of deciduous forests belong to the union of Chelidonio-Robinion Hadac et Sofron 1980 and towards improving wetting habitats are distributed, respectively, into three associations: Galio aparines-Robinietum Scepka 1982 prov., Chelidonio-Robinietum Jurko 1963 and Sambuco nigrae-Robinietum Scepka 1982 prov. Spontaneous stands of Acer negundo mixed with other deciduous trees in hygro-mesophilic conditions – floodplains, thalweg ravines, slopes of river valleys are attributed to the Union of Chelidonio-Acerion negundi L. Jshbirdina et A. Jshbirdin 1989 and associations of Chelidonio-Aceretum negundi L. Jshbirdina et A. Jshbirdin 1989. Conclusion.The groups of the class has field-protective, water- and snow-detaining, microclimate functions and is an important source of honey harvesting. Therefore, their existence is justified in the arable land and settlements. Regarding forest stands of Robinia pseudoacacia and Acer negundo in the forests, they must be subject to clear-cutting with the destruction of undergrowth to change species to native species of trees.

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