SUCCESSIONAL DYNAMICS OF SECONDARY PHYTOCENOSES OF COASTAL AJARA UNDER ANTHROPOGENIC TRANSFORMATION AND BIOLOGICAL INVASIONS

Abstract

Coastal Adjara is one of the most dynamic subtropical regions of Georgia, where intensive urbanization, recreational pressure, expansion of transport and construction infrastructure, land-use change, and the long historical introduction of plants have a significant influence on the structure and developmental dynamics of natural and secondary vegetation. The warm and humid climate of the region, the long growing season, and the extensive network of anthropogenically transformed habitats create favorable conditions for the establishment and naturalization of alien plants and for the invasive spread of individual species.

The aim of the study was to assess the structure and successional dynamics of secondary phytocenoses of Coastal Adjara, determine the role of anthropogenic factors and biological invasions in their transformation, as well as characterize the agrochemical and multi-element status of the Red Soils of the Gonio–Sarpi transboundary section. The study included urban and suburban territories, roadside and recreational habitats, abandoned agricultural lands, secondary vegetation of the Batumi Botanical Garden and its surrounding territories, as well as the Gonio–Sarpi coastal zone.

Route-reconnaissance, phytocenological, agrochemical, and multi-element research methods were used. The structural characteristics of secondary plant communities, the participation of alien species, and the main directions of secondary succession were assessed. Analysis of the Red Soils of the Gonio–Sarpi transboundary section revealed a strongly acidic reaction (pH 3.2–3.5), low contents of humus (1.2–1.9%) and total nitrogen (0.032–0.041%). The contents of the main plant nutrient elements were: K – 9.7–13.4, Mg – 12.3–15.6, Ca – 28.4–38.5, and P – 10.72–17.28 mg/kg. Multi-element analysis revealed relatively high contents of Al (51.2–113.28 mg/kg), Fe (42.6–65.32 mg/kg), and Si (23.8–46.7 mg/kg), while concentrations of Cu, Cd, and Mo exceeding the corresponding threshold values indicate a possible anthropogenic chemical load.

The results of the study showed that the nature and intensity of anthropogenic pressure influence both the chemical status of the soil and the structural and successional dynamics of secondary phytocenoses. Urban-suburban ecotones, roadside, abandoned, and coastal habitats are particularly vulnerable to biological invasions and represent important centers for the establishment and subsequent spread of alien species. The increasing participation of alien species changes the floristic composition and successional trajectories of communities and may hinder the natural recovery of native vegetation. The obtained results provide a basis for integrated monitoring of soil and vegetation, identification of habitats with high ecological risk, and sustainable management of transformed ecosystems of Coastal Adjara.