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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]

Understanding ecological processes and environmental change in different urban green spaces is an important challenge to secure human well-being. The variety of urban green spaces provides a platform to generate knowledge on how urban environments affect tree leaf decomposition and quality. We measured the leaf litter decomposition of four dominant native deciduous tree species from five different urban green spaces over three time periods in Kaunas, Lithuania. Using the modified litter bag technique, we calculated the decomposition of 60 leaf litter samples for 4, 8, and 12 months respectively. For each leaf litter sample, we determined total N, total P, and organic C. Results indicated that the decomposition of leaf litter amongst tree species, urban green spaces and seasonality (time) were significantly different. The leaf litter of Betula pendula and Acer platanoides from street green spaces decomposed fastest during the spring-summer period. Quercus robur showed small but significant leaf litter loss differences between the green spaces, with the leaf litter from peri-urban forest decomposing the fastest. A decreased C:N ratio for Q. robur leaf litter showed accelerated leaf litter decay. In conclusion, our results show that the ecological processes of leaf litter decomposition, differs between tree species, type of urban green spaces and seasonality and thus must be considered in urban town planning to help maintain urban environments. [ABSTRACT FROM AUTHOR]