Biological invasions in last relicts of Pampas grasslands (Argentina): impact and management

SERGIO ZALBA; YANNINA CUEVAS; ANA ELENA DE VILLALOBOS; CRISTINA SANHUEZA; LEANDRO DISPIGNO; ENRIQUE ZUCCHINO; ALEJANDRO LOYDI

Brasilia

Congreso; 19th Annual Meeting of the Society for Conservation Biology; 2005

Ernesto Tornquist Provincial Park (Buenos Aires, Argentina) is one of the last relicts of Pampas grasslands. Invasion by exotic species, especially feral horses, pines (Pinus spp.) and Spanish broom (Spartium junceum), stands out as one of its main conservation challenges. In 1994 we started research and management activities directed to reduce their impact. We found that pines and broom invasions result in significant reductions in the diversity of native plants and in changes in bird and terrestrial invertebrates communities. Feral horses in turn are responsible for increasing the abundance of woody plants and the proportion of bare soil. In all this cases we observed that these species facilitate the establishment of other aliens. Fire promotes the releasing of seeds from pines cones and their establishment and also produce the depletion of brooms seed banks. Mechanical control (cutting with chain-saws) is highly effective for pines. Spanish brooms showed 50% mortality when treated with fire and with a combination of cutting and herbicides, with significant differences depending on plant size. Lack of public appreciation about the value of native grasslands appears as the critical issue for managing these invasions and we started an education strategy directed to the local community.