Document: FER-3-82-29

Monitoring the invasion of woody exotic species in the "El Palmar" National Park (Argentina) using remote sensing.

SELMO, F.E.R.* ¹, M.FERNANDA MENVIELLE ², A.L.SCOPEL ¹ and P.MINOTTI ³

Universidad de Buenos Aires, Buenos Aires, Argentina ¹
Administración de Parques Nacionales, Buenos Aires, Argentina ²
CAECE, Buenos Aires, Argentina ³

Abstract:
"El Palmar" National Park (31 55' S, 58 16' W) is an 8,500 ha relict of a temperate savanna ecosystem dominated by the palm tree Syagrus yatay, embedded in a matrix that has been drastically modified by human activities. The exogenous disturbances together with the changes in management practices since the park was created (e.g., exclusion of grazing, fire suppression) have contributed to the invasion by exotic woody species. In this study we analyzed the spatial and temporal changes in the invasion of the woody exotics: Melia azedarach, Gleditsia triacanthos and Piracantha atalantoides by using Landsat TM imagery for 1984, 1994 and 1999. A supervised classification of the images was done on the basis of the spectral signature of each species. In a period of 15 years, the area that is severely invaded has undergone a 5-fold increase, currently expanding to more than 5 % of the park's surface. This increase is mainly derived from the expansion of previously existing foci, some of which had been planted long before the park was created. Gallery forests, shrubby savannas and palm forests have been the environments most affected by these invasions, while grasslands have remained almost unperturbed. Melia azedarach is by far, the species showing the greatest invaded area, with multiple expanding foci scattered throughout the park. Although the resolution of Landsat TM images does not allow to detect the presence of the smallest foci, ground measurements are revealing that the species is present in at least 70 % of the park's surface. Gleditsia triacanthos and Piracantha atalantoides exhibit a more limited range of distribution, with fewer but bigger foci. The study of the distribution and spatial pattern of these exotic species, together with basic knowledge of the population demography and history of management, are key to unravel the mechanisms and causes of the invasive process when aimed at planning the management of protected areas.

Keywords: plant invasions - palm savannas - remote sensing - protected areas

This abstract is being presented at: 10:30 AM in session:
RESTORATION ECOLOGY AND INVASIONS