Resumen

DEMARIA, Manuel R; AGUADO SUAREZ, Inmaculada  y  STEINAKER, Diego F. Semiarid pampa grassland replacement and fragmentation in San Luis, Argentina. Ecol. austral [online]. 2008, vol.18, n.1, pp.55-70. ISSN 1667-782X.

Understanding rates of natural grassland transformation and fragmentation and their relation with soil and climatic characteristics is relevant for identifying potential conservation sites, for sustainable management and for land-use planning. In this study, five Landsat images (1985, 1992, 1997, 1999, 2001), covering 4129.9 km², were used to quantify the amount of natural grassland areas replaced by exotic pastures or crops, and to analyze the pattern and rate of change of these grasslands in a 16-year period. Grassland transformation rates were measured using a mixed classification and post-change detection method. A fuzzy classification was used to analyze changes in proportions of bare soil. Auxiliary data (an agronomic aptitude map, an ecological condition map and paddock subdivisions) were related with the classified images to analyze ecological patterns. Image classification showed that between 1985 and 2001, natural grassland cover was reduced from 84.5 to 37.8% and that the annual transformation rate increased significantly from 1.4 to 10.9%. Furthermore, the proportion of bare soil and incidence of fragmentation increased, especially in the most productive areas (fragmentation rose from 463 to 800 paddocks). This work provides relevant data for land management planning that integrates productive and conservationist criteria. However, the creation of protected areas and the implementation of sustainable management is a decisive challenge for the conservation of the semiarid pampa ecosystem.

Palabras clave : Change detection; Land use; Landsat TM; Remote sensing; Supervised, unsupervised and fuzzy classification.

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