Investigation of regeneration and spreading of black locust (<i>Robinia pseudoacacia</i> L.) in Lithuania

Abstract Black locust ( Robinia pseudoacacia L.), a North American species, naturalized in Europe many years ago, falls into the category of alien species with insufficient and controversial information. In Lithuania this species is mostly found in farmsteads. It is frequently cultivated along roadsides. However, it is relatively rare in forests. Robinia pseudoacacia found new habitats during the rapid globalization period due to intentional human activity or random factors. In Lithuania, black locust, as an invasive species spreads in certain ecotops relatively such as Curonian Spit. The black locust does not behave uniformly across different ecotopes and climate zones. Thus, to successfully manage the species abundance, scientific investigations are essential. The aim of these studies was to evaluate the black locust ( Robinia pseudoacacia L.) spreading in open areas and adjacent stands. Investigations were carried out in the Jonava and Kretinga Regional Divisions of State Forest Enterprises (SFE) allocated temporary sample plots, where species composition contained black locust. The recovery of black locust under tree crowns was small and exceed only about 122 units / ha. The black locust spread into open spaces from the maternal plant at the distance of 8-32 meters in average. Prevailed the saplings in 1 and 2 hight groups and their relative share increase moving away from biogroups (coppice). Of all the records on the saplings 96.6% was formed from the root suckers and only 3.4% – regenerated from seeds. After conducting a seed germination study under natural conditions, it was determined that the germination rate was low, at about 2.5%. The seeds germinated only in the mineral firebreak when sown on the surface and in mineral soil on the surface.