Alien woody plants in the Ulytau region: invasive potential and naturalization pathways

This study is devoted to the distribution and ecological assessment of alien tree and shrub species in the Zhanaarka and Ulytau districts of the Ulytau region in Central Kazakhstan. The relevance of the topic is due to the need for early detection and assessment of the potential invasive threat of introduced species in steppe and forest-steppe ecosystems that are vulnerable to external influences. The study aimed to identify alien woody plants in the natural biocenoses of the region. The research tasks included determining the naturalization status of invasive species, establishing the possible source of their spread, assessing the aggressiveness and scale of their spread, assessing the threat to native flora, and ways to reduce the risk of invasive plants entering natural plant communities. Research shows that the assessment of alien dendroflora in this region has not been studied before, especially with regard to the degree of naturalization, the nature of distribution, and the impact on native vegetation. The work uses field route surveys, taxonomic analysis, an invasiveness assessment scale based on a modified classification from the “Code for the Management of Invasive Alien Plant Species in Botanical Gardens of the CIS Countries,” as well as methods of comparative floristic analysis. As a result of research in the Ulytau region, 21 alien tree taxa were identified, mainly cultivated as part of forest reclamation measures or greening of settlements. It was found that alien woody plants such as Acer negundo, Populus balsamifera, and Fraxinus americana mainly show sporadic distribution without displaying a high degree of aggressiveness (rank 0–3). However, the presence of isolated seedlings outside the parent crowns and signs of generative activity in some taxa indicate a potential invasive threat. The data obtained are of practical importance for planning reforestation and nature conservation measures in arid areas of Kazakhstan.