Invasion determinants of honey locust in agroecosystems of the Rolling Pampa, Argentina

Abstract

The honey locust (Gleditsia triacanthos) is one of the most aggressive tree invaders of savannas and grasslands worldwide. The objective of the study was to determine whether landscape elements could act as potential determinants on honey locust invasion of woodlots of an agricultural matrix of the Pampean ecoregion. Specifically, we assessed the effect of distance to the previously established woodlots, to corridors such as riparian habitats, railway terraces and roads, and the presence of livestock and land use through generalized linear models. The study was carried out in a rural area of the Exaltación de la Cruz Department of the Buenos Aires Province (34°19’ S and 59°14’ W), located in the Pampean ecoregion, in the Rolling Pampa complex, Argentina. In each woodlot, the presence or absence of honey locust and the number of individuals intercepted along line transects were recorded. Furthermore, the presence of cattle and the land use around the woodlot were registered. All woodlots were geo-positioned to calculate distances to landscape elements of interest. According to our results, the colonization capacity and the abundance of honey locust increases as distance to the nearest woodlot with the presence of the species decreases, suggesting that propagule pressure is a key factor for honey locust invasion. Also, cattle promote the increase in the abundance of the species in woodlots of the agricultural system studied. The probability of presence was also increased with the proximity to main roads and decreased with the proximity to the nearest human settlement. Our results highlight the importance of reducing the abundance of the species in invaded woodlots and cattle pathways and in case of moving animals from an invaded to a non-invaded area. It is also recommended to maintain animals in quarantine before transporting them in order to allow animals to eliminate honey locust seeds.