Evaluation of composition of herbaceous plant species in the sites with Impatiens parviflora DC

Abstract

Nowadays invasion of alien species may threaten the most remote habitats altering unique composition of native species. Invasive plants have a tendency to adapt swiftly to different conditions of environment and settle in versatile habitats. Small balsam (Impatiens parviflora DC.) is a widespread invasive plant which managed to pervade the majority of European countries through the last century. The aim of this study was to evaluate the structure of various Lithuanian sites with small balsam populations using set of phytocenological parameters. Scattered across Lithuania 21 population of small balsam were selected for our research. At each site composition and coverage by herbaceous plant species was assessed in 100 m2 plots. Abiotic environment (light, temperature, continentality, soil moisture, pH and nitrogen) was evaluated using weighed Ellenbergind icatory values. In our study sites depending on habitat type coverage by small balsam ranged from 5% (Žagarė) to 70% (Kaunas-Aukštieji Šančiai, Juodkrantė), mean being 35%. By two-way cluster analysis all herbaceous plant species and populations were grouped into several clusters. The most distinct was plant community in Žagarė (32 herbaceous plant species) with the lowest small balsam coverage (5 %). Urtica dioica L.was the only species found in all study sites. Principal coordinate analysis, based on Ellenberg weighed indicatory values, has grouped small balsam populations into four clusters. Žagarė population formed a separate cluster because of unique geographical and habitat features. The next level clusters (from the second down to the 4th degree cluster) have encompassed populations with increasing coverage by small balsam whereas decreasing values of Ellenberg light and moisture estimates. It might be concluded, that for growth of small balsam preferable sites are shaded areas with moderate soil moisture.