Lowland deciduous thorn woodland & shrubland geocomplex. 1. Deciduous thorn-woodland and shrubland: Senegalia emilioana-Schinopsis quebracho-colorado community. Zonal medium drained clay-silty soils (regosols and luvisols). 2. Deciduous woodland on deep sandy soils: Senegalia emilioana-Schinopsis cornuta community. Sand dunes and eolic surfaces (arenosols). 3. Flooded palm-woodland: Prosopis ruscifolia-Copernicia alba community. Interdune temporarily ponded depressions (clay solonchaks). 4. Xeromorphic shrubland: Aspidosperma triternatum-Bulnesia sarmientoi community. Poorly drained clay soils with strong gilgai microrelief (eutric vertisols). 5. Phreatophyllous thorn-woodland: Vallesia glabra-Prosopis chilensis community. Alluvial clay silty soils with shallow water table (gleyic luvisols). 6. Seasonally flooded thorn-woodland: Coccoloba guaranitica-Geoffroea spinosa community. Seasonally ponded with stagnant waters (gilgai vertisols and stagnosols). 7. Palm-woodland: Triplaris gardneriana-Copernicia alba community. Seasonally flooded with mesotrophic flowing waters (sodic humic eutric vertisols and fluvisols). 8. Riverine forest: Crataeva tapia-Albizia inundata community. Seasonally flooded with mesotrophic flowing waters (gleyic humic eutric fluvisols). Graphic geobotanical interpretation based on cited references, our own numerous field data (1993 to 1998), and Google Earth images.