The results of studying introduced species diversity and state under rainfed conditions at the Research station of the Institute of Forest Science of the Russian Academy of Sciences have been presented. The station is located in the clay semi-desert of the Northern Pre-Caspian region between the Volga and Ural rivers. The collections of two arboreta were examined. The first arboretum was established in 1953 on hydromorphic meadow-chestnut soils of large mesodepressions, and the second – in 1974 on solonetzic automorphic soils. The arboreta were originally established with an idea of complete elimination of irrigation. In recent decades, tending and silvicultural treatments were discontinued for a number of reasons. An annotated list of tree and shrub species includes 77 species belonging to 25 families and 44 genus. In the arboretum on the large mesodepression, the number of species surviving for more than half a century is 35% in relation to the number of “core” introduced species. Mostly, the species are represented by the families Rosaceae, Caprifoliaceae, Elaeagnaceae, Fagaceae, Fabacea, Oleaceae, Salicaceae, Sapindaceae, Ulmaceae. Some specimens older than 70 years are in satisfactory condition and produce viable volunteer regrowth. The main stages of their acclimatization, in relation to age, and changes in growing conditions, as affected by plants themselves as well as climate, are distinguished. In arboretum on solonetzic soils, the survival of species is 50%. The composition of tree and shrub vegetation of an unused pond, where spontaneous vegetation formed an intrazonal willow-oleaster-poplar community of quasi-riparian type, and of the overgrowing fallow land, where a specific “savannah-like” landscape was formed, have been studied. This allowed to identify the species whose life strategy contributes to their successful colonization of human-disturbed habitats and, in some cases, manifestation of the features of naturalization and invasiveness. The most promising species for landscaping, parks and other plantings in such harsh natural and climatic conditions were also determined.
