A spontaneous spread of black locust (Robinia pseudoacacia L.): the importance of seed and vegetative reproduction

The importance of seed and vegetative propagation for the spontaneous expansion of black locust on abandoned agricultural land was evaluated in the present study. The dynamics of expansion was reconstructed on the basis of spatial distribution data on the age of individuals of this species. A non-homogeneous Poisson process with a linear trend and a Widom-Rowlinson model were the most appropriate in explaining the spatial distribution of R. pseudoacacia individuals. The negative linear trend was statistically significant for the vast majority of polygons in the area of spontaneous expansion of R. pseudoacacia, but insignificant in the artificial plantation. The model parameter η indicates the aggregated spatial distribution of R. pseudoacacia in the zone of spontaneous spread due to the vegetative mechanism of spread. The distribution of R. pseudoacacia in the artificial tree plantation was close to regular, or either random or aggregated. In the early stages, the seed reproduction is the most likely process of R. pseudoacacia spreading. The seed mechanism of spreading follows a spatial pattern, which is explained by a linear trend. The next stage is a combination of both seed and vegetative mechanisms of spread, which also lasts about 4–5 years. At the last stage, the spread occurs mainly through the vegetative mechanism, and the rate of spread of the community slows down significantly. The trigger for the spread is anthropogenic impact.