Classification and ecological assessment of vegetation in the afforestation belts of the Left−Bank Forest−Steppe of Ukraine

Afforestation belts are key components of transformed agricultural landscapes in the Ukrainian Forest−Steppe. Established during the 19th and 20th centuries, these 60−100−year−old linear plantations are undergoing advanced natural aging, canopy degradation, and spontaneous sylvan succession. Despite their artificial origin, they have developed into unique forest−like biotopes with distinct phytocoenotic structures, exhibiting an ecological duality that balances agroecological protective functions with spontaneous development. This study assesses the syntaxonomic diversity, structural organization, and ecological characteristics of afforestation belts in the Left−Bank Forest−Steppe of Ukraine in relation to macroclimatic and edaphic gradients. The study is based on 95 relevés. Vegetation classification followed the Braun−Blanquet approach and was aligned with the Prodromus of the Vegetation of Ukraine. Habitat ecological status was evaluated via phytoindication using Didukh’s ecological scales, mathematically rescaled to a unified 100−point standardized scale. Environmental differences across syntaxa were verified using one−way ANOVA with Tukey’s HSD post−hoc test (p<0.05). Detrended Correspondence Analysis (DCA) with vector fitting was employed to visualize vegetation distribution and uncover socio−ecological gradients. The shelterbelt vegetation was classified into five associations within the synanthropic class Robinietea (order Chelidonio−Robinietalia pseudoacaciae), split between two alliances: Geo−Acerion platanoidis (Ass. 1: Elytrigio repentis−Aceretum platanoidis; Ass. 2: Poo nemoralis−Tilietum cordatae; Ass. 3: Geo urbano−Fraxinetum) and Sambuco nigrae−Quercion roboris (Ass. 4: Elytrigio repentis−Quercetum roboris; Ass. 5: Sambuco nigrae−Quercetum roboris). Communities exhibit clear vertical stratification with well−developed woody (average cover 0.68/68%) and shrub (0.48/48%) layers, whereas the poorly developed herb layer (0.20/20%) facilitates alien plant invasions. The overstory is dominated by autochthonous Quercus robur, Acer platanoides, Tilia cordata, and Fraxinus excelsior, though invasive species are widely naturalized. Phytoindication identified soil acidity (Rc), nitrogen (Nt), and moisture (Hd) as primary drivers of differentiation. Baseline conditions correspond to moderately moist (Hd 43.6), near−neutral (Rc 60.7), and low−salinity (Sl 34.2) soils. ANOVA confirmed significant ecological differences, particularly along the nitrogen gradient between Geo urbano−Fraxinetum and Elytrigio repentis−Quercetum roboris. DCA ordination demonstrated distinct floristic differentiation driven chiefly by soil acidity and canopy light transmittance. The results indicate that afforestation belts are dynamic ecosystems undergoing successional transformation influenced by canopy architectonics, microclimatic buffering, and intense anthropogenic factors. Severe edge effects and massive nitrogen runoff from adjacent arable fields maintain these communities in a eutrophicated ecotonal state. Acting as vital biodiversity refugia, migration corridors, and zones highly susceptible to biological invasions under macroclimatic warming, these communities require targeted, long−term management and conservation strategies.