Evaluación del banco de semillas y reclutamiento de la especie exótica invasora tojo (Ulex europaeus L.) en un predio ganadero de la región este del país

Ulex europaeus, also known as “gorse”, “common gorse” or “prickly broom”, is listed as one of the four invasive exotic plants of greatest risk for Uruguay. Its distribution in the country is mainly concentrated in the east and northeast of the country. This invasive exotic species (IAS) decreases the productivity of natural fields and interferes with the use and exploitation of the soil. Given the invasiveness of the species, we seek to provide knowledge about the long-distance sexual dispersal strategy. The objective of the work was to analyze the seed bank and recruitment of seedlings of the U. europaeus species based on a spatial gradient, from an area with gorse patches to 35 m away from the patches. The specific objectives were: i) to quantify the size of the seed bank and the density of seedlings in a non-invaded area adjacent to U. europaeus patches, and ii) to estimate the density of seedlings on the outer edge of the U. europaeus patches. For this purpose, two surveys were carried out on a livestock farm in the Lavalleja department (34°08'03.1"S, 55°13'01.5"W). In the first, the number of seedlings was counted and for the seed bank, soil samples were taken from 3 m from the outer edge of gorse patches up to 35 m. Ten 30-m-long transects were made across a slope and measurements were taken every 10 m. In the second sampling, an area on the edge of gorse patches was evaluated by making a 30-m border with 15 points, located 2 m apart, where seedlings were counted. In the first sampling, no seeds or seedlings were found at 0, 10, 20, 30 m from an area of ​​U. europaeus patches. However, the presence of seedlings was observed in a patch border area at a density of 21 seedlings/m2). We can confirm that at this site and according to the literature, seed dispersal would occur in the surroundings of the mother plant, and that dispersal over a distance greater than 3 m would be an unlikely event. Dispersal over greater distances would be rare events and the agents of which are still unclear. The present study seeks to make visible the importance of controlling and preventing IAS and provides knowledge to understand the sexual dispersal of U. europaeus.