The spatial distribution of vegetation patches influences physical, demographic and community use processes. Understanding these processes allows the optimization of conservation efforts. The Celtis tala forests (locally Talares) area, Northeast Buenos Aires Province, is an environmental mosaic where thorny forests and woodlands patches combine with humid grasslands and coastal communities of La Plata river. The efficient selection of areas for biodiversity conservation helps to increase the aimed conservation targets and reduces the cost of involved activities. The landscape structure of the Talares was analyzed to identify high-priority conservation areas on the base of forest fragmentation, diversity of vegetation categories and its contrast degree. We did a digital map of the study area with five cartographic unit types named according to dominant vegetation. These types, defined by tree cover range and the native or planted character, were native closed forest, woodland, tree-grassland (a tree savanna-like grassland), grassland and tree plantations. Indexes of landscape diversity (Shannon & Wiener), continuity or inverse of fragmentation (area of dense forest / border length) and contrast were calculated. High-priority conservation areas were identified as those with low fragmentation, high diversity and high contrast; they correspond to sectors with extensive patches of closed forest and less border, and to sectors with equitative fractions of different vegetation units. In this way, the selected sectors would include appropriate areas for species with different habitat requirements increasing potential biodiversity in protected areas.

Key words: Temperate thorny woodlands, conservation, fragmentation, contrast, landscape diversity.