Privet invasion in the understory of an araucaria forest remnant: a demographic approach

The replacement of native species by invasive species has caused a worldwide loss of biodiversity. This study aimed to evaluate the natural regeneration over time in a forest fragment invaded by Ligustrum lucidum W.T. Aiton and Ligustrum sinense Lour. in southern Brazil, in order to quantify this invasion. To do so, five transects were allocated in a fragment of Araucaria Forest in Lages, Santa Catarina state, with each transect divided into plots in different categories of distance from the edge and into sub-plots for the evaluation of the regenerative component. In 2012, the regenerating tree species identified in the sub-plots were tagged and classified according to height classes: Class 1, plants with height between 10 cm and 1 m; class 2, plants with height between 1 and 3 m; and Class 3, plants with a height greater than 3 m and DBH (diameter measured at breast height) less than 5 cm. In 2014, these individuals were re-evaluated, counting the dead and recruited individuals and classifying the survivors and recruits into the existing height classes. Rates of mortality, recruitment, net change, and height class changes were calculated. The data were analyzed by a Principal Component Analysis (PCA) and contingency table. It was concluded that the species overcame the early stage of the invasion process, demonstrating great population growth in the study area. Also, a spatial partitioning between native and exotic species was observed, suggesting the existence of interspecific competition, the result of which may be the local extinction of species from the autochthonous group.

Keywords:
Forest dynamics; Invasive exotic species; Privet tree