Volumen 20 No. 2 - Especial de Biología, Bosque Seco - diciembre 2016 13 Facultad de Ciencias Naturales y Exactas Universidad del Valle Vegetation Composition and Structure of Tropical Dry Forest Fragments and of Two Sites with Anthropic Activity in La Dorada and Victoria, Caldas Jhon Alexander Vargas Figueroa Ángela María González Colorado Universidad del Valle Universidad del Valle Eliana Barona Cortés Wilmar Bolívar García Universidad del Valle Universidad del Valle Recibido: March 2, 2016 Aceptado: August 22, 2016 Pag. 13-60 Abstract The excessive degradation of the ecosystems from the tropical dry forest formation urges us inmediataly to carry out studies as a strategy for conserving the biodiversity in Colombia. We characterized the vegetation of fragments of these ecosystems in the Magdalena Medio basin. We deined Mining Zones (MZ), Unmanaged Silvopastoral System Zones (SZ) and Forests Zones (FZ). We ramdomly localized 20 transect per zone (50x2m). We sampled trees, shrubs, lianas (DBH≥1cm), and herbs in ive quadrants (1m²) per transect. We completed the loristic inventory with free collections. We recorded 506 species in 90 families. Fabaceae presented the mayor speciied richness in all the zones; Cyperacea and Poaceae were the second and third richest families in MZ; Malvaceae and Euphorbiaceae were the richest species in SZ, and Rubiaceae were the richest in FZ. FZ had more species richness and more individual abundance than sites with anthropic activities. MZ does not have a deined vertical structure. SZ has a composition and vegetation structure similar to sites with early plant succession and FZ has a more complex composition and vegetation structure. FZ records much higher species richness per area unit than dry forests from the south of the Magdalena valley, but a lower one than the rainforests from the north, which makes these fragments a potential and important ecological connection point. Keywords: plant succession, mining, silvopastoral system, Magdalena valley. Composición y estructura vegetal de fragmentos de bosque seco tropical y de dos zonas con actividad antrópica en La Dorada y Victoria, Caldas Resumen La excesiva degradación de los ecosistemas de la formación de bosque seco tropical, obliga a su inmediato estudio como estrategia para conservar la biodiversidad en Colombia. Se caracterizó la composición y estructura vegetal de fragmentos de estos ecosistemas en el Magdalena Medio, para aportar a la evaluación de su estado. Se delimitaron zonas de minería (ZM), sistema silvopastoril sin manejo (ZS) y bosque (ZB). Se ubicaron al azar 20 trayectos lineales (50x2m) por zona. Se censaron árboles, arbustos, lianas (DAP≥1cm) y también hierbas en cinco cuadrantes (1m²) por trayecto; se