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Robinia pseudoacacia is an alien tree species that has wide distribution in green areas of Rīga and Kaunas. In recent years, the spread and invasion of this species was observed. The aim of this study was to determine the relative importance of invasiveness of R. pseudoacacia in Rīga and Kaunas. The degree of species invasion was estimated by applying the Pest Plant Prioritization Process, which is based on the Analytic Hierarchy Process method. The results showed that the invasive degree of R. pseudoacacia was near medium (0.4); the present compared to potential distribution rating was medium (0.57) and the social, environmental and economic impact score was very low (0.17). The Final Pest Plant Score for R. pseudoacacia was near medium (0.426). The obtained estimates indicated that black locust was medium invasive, and that well-lit conditions favour its establishment. [ABSTRACT FROM AUTHOR]

Ashleaf Maple (Acer negundo L.) was first introduced in Latvia and Lithuania at the beginning of the 19th century. It is the most widely distributed alien maple species to be found in the parks and greeneries of Riga and Kaunas. In recent decades, the spread and invasion of this species has been observed. The aim of this research was to determine the extent and effects of the invasiveness A. negundo in Riga and Kaunas. The degree of invasion by this species' was estimated by applying the Pest Plant Prioritization Process, which is based on the Analytic Hierarchy Process method. The results showed that the invasive degree of box elder was very high (0.788); the present compared to potential distribution rating was medium high (0.71) and the social, environmental and economic impact score was low (0.23). The Final Pest Plant Score for A. negundo was medium (0.4506). The obtained estimates indicated that box elder was invasive and was able to spread rapidly into new riparian areas. [ABSTRACT FROM AUTHOR]

This study investigates the effect of climate variability on the phenotype, leaf litter decomposition intensity and seedling spread of alien red oak (Quercus rubra L.). Twenty-eight red oak forest stands located in Lithuania were evaluated. Indirect climate change indicators such as continentality were used in the analysis. Simulation of climate warming was achieved using an agro sheet cover. According to the results, the morphological traits of red oak stems in the maritime regions (warmer winters) do not differ significantly from those of red oaks stems in the continental areas of Lithuania (colder winters, more frequent spring frosts). Red oak leaf litter under an agro sheet cover (warmer conditions) decomposes at almost the same intensity as without the cover (natural conditions). The red oak seedlings spread 100 m or more irrespective of continentality. These results showed indirectly that climate change will not affect red oak stem quality or microorganism activity in the process of leaf litter decomposition. Red oak will thus remain as an invasive species, threatening composition change in native forests. [ABSTRACT FROM AUTHOR]

In the context of global change, the integration of non-native tree (NNT) species into European forestry is increasingly being discussed. The ecological consequences of increasing use or spread of NNTs in European forests are highly uncertain, as the scientific evidence is either constraint to results from case studies with limited spatial extent, or concerns global assessments that lack focus on European NNTs. For either case, generalisations on European NNTs are challenging to draw. Here we compile data on the impacts of seven important NNTs (Acacia dealbata, Ailanthus altissima, Eucalyptus globulus, Prunus serotina, Pseudotsuga menziesii, Quercus rubra, Robinia pseudoacacia) on physical and chemical soil properties and diversity attributes in Europe, and summarise commonalities and differences. From a total of 103 publications considered, studies on diversity attributes were overall more frequent than studies on soil properties. The effects on soil properties varied greatly among tree species and depended on the respective soil property. Overall, increasing (45%) and decreasing (45%) impacts on soil occurred with similar frequency. In contrast, decreasing impacts on biodiversity were much more frequent (66%) than increasing ones (24%). Species phylogenetically distant from European tree species, such as Acacia dealbata, Eucalyptus globulus and Ailanthus altissima, showed the strongest decreasing impacts on biodiversity. Our results suggest that forest managers should be cautious in using NNTs, as a majority of NNT stands host fewer species when compared with native tree species or ecosystems, likely reflected in changes in biotic interactions and ecosystem functions. The high variability of impacts suggests that individual NNTs should be assessed separately, but NNTs that lack European relatives should be used with particular caution. [ABSTRACT FROM AUTHOR]