The black locust (Robinia pseudoacacia) population vital state in the urban ecosystem

Many European countries have extensively practiced the cultivation of black locust. This species is characterised by rapid growth, the application possibility for degraded land reclamation and other useful properties, but its adventiveness and invasive status require more thorough research. The aim of the research was to assess the viability of a population of black locust (Robinia pseudoacacia) in urban environment by determining its vital status and measuring height of the plants and diameter of their trunks as the main morphometric indicators. The research was conducted in the recreational area of the Oles Honchar Dnipro National University Botanical Garden. There were recorded 178 plants of R. pseudoacacia. Tree heights were measured by a Suunto PM-5 mechanical height meter in three-time repetition for each plant, and the average value was calculated based on these data. The trunk diameter was measured at the small fork as a distance between two parallel tangents. The vital status of the trees was determined by the 5-point scale of V. A. Alekseev. The height of the vast majority of the studied trees varied 25 to 30 m. The height of one species representative reached 32 m. The trunk diameter of the most trees in the territory ranged 30 to 40 cm. Plants with a trunk diameter of between 40 cm and 50 cm were the next largest group. A 101 cm trunk diameter was found in just one tree. Most plants in the research area had a vitality score of 2 – good state. Accordingly, these were the plants that had the largest trunks of examined trees. The fewest number of plants was in a very bad state and had a score of 5. The good and satisfactory vital conditions were observed in plants whose trunks were the tallest and had the largest diameter, and whose morphometric indices slightly varied (the height-diameter trunk correlation was reliable). Plants in depressed and poor vital state were characterised by significant variability in the morphometric parameters (the correlation between height and trunk diameter was not reliable). The ecological condition of the black locust population in the area was assessed, and it was concluded that its morphometric parameters cannot be used as indicators of plant vitality.