Urban forest condition and succession in the abandoned city of Pripyat, near Chernobyl, Ukraine

Following the April 26, 1986, accident at the Chernobyl nuclear power plant (Ukraine), the nearby city of Pripyat was contaminated and then quickly abandoned with its urban trees largely intact, resulting in a unique “city forest” that has remained un-maintained for over one-quarter of a century. We assessed the composition and condition of city trees in Pripyat, and documented the process of ecological succession in an attempt to predict the future urban forest, by surveying trees on 40 plots distributed across 4 urban tree habitats (street-side, tree grove, lawn, and pavement). The plots contained 20 species of trees, and were dominated by the seedling age-class, with as many as 8980 Acer platanoides seedlings/ha. Among the urban habitats, street-side and tree grove plots had the highest density of regenerating trees. Regeneration varied by species, with some (e.g., Populus nigra 'Italica') regenerating in every plot where mature trees were present, while others (e.g., Aesculus hipocastaneum) not regenerating at all. Based on the regeneration patterns and tree species characteristics, we expect the future urban forest of Pripyat to contain a mosaic of oak/maple areas (street-side, grove, and lawn habitats) with poplar/aspen areas on the pavement habitat. Condition of mature trees was good in over 50% of surveyed trees, while the rest exhibited the defects common to other urban trees (e.g., co-dominant stems), but also displayed characteristics generally absent from trees in other cities (e.g., very high live crown ratios). In its current age-distribution, species composition, and condition of its urban trees, Pripyat demonstrates the ongoing change from the primacy of anthropogenic factors (e.g., trees selected for ornamental characteristics) to ecological ones (e.g., shade tolerance) in shaping the composition and condition of an abandoned urban forest.