Regeneration and early tending of black locust (Robinia pseudoacacia L.) stands in the north-west of Romania

Aim: The aim of this study is to highlight the importance of black locust (Robinia pseudoacacia L.) on extreme site condition like sand dunes. Aspects of natural regeneration and early results of tending operation in terms of quality, growth and yield of young black locust stand are presented. Methodology: A Research and Development project was carried out in Carei-Valea lui Mihai Plain (north-west of the country) since 2016. Three management units were selected: pure natural regeneration by root suckers of black locust at different ages (management units 3B and 52A%) and a mixed black locust-black cherry stand (management unit 23D). Biometrical measurements and analyses as well as biomass estimations were performed. Results: (1) Black locust was established naturally by root suckers and the stocking of newly established stands can be as high as 50,000 suckers ha-1; (2) The initial growth of black locust regeneration is quick and the young regeneration can close the canopy in 1-2 years, resulting in an appropriate dune fixation and wind erosion control; (3) The young pure or mixed black locust-dominated stands are left untended until the first cleaning-respacing (mean diameter 5-6 cm), when the stand shows high stocking/density and a wide variation in tree size. This intervention is from below, heavy (intensity over 25% by number of trees or basal area) and of negative selection type, removing mostly low Kraft class, dead or dying, and defective trees. Interpretation: The potential of black locust to establish naturally by root suckers and their fast initial growth, despite the unfavourable conditions in the case study area, resulted in effective dune stabilization and wind erosion control. The effect of cleaning-respacing on the early growth of this species in pure or mixed stands was outlined.