Silvopastoral systems and ant diversity conservation in a cattle-dominated landscape of the Colombian Andes

Abstract

Conventional cattle ranching in Latin America has been based mostly on extensive pasture monocultures planted with minimum tree cover. The current trend towards replacing treeless pastures with silvopastoral systems that include tree and shrub species enhances productivity and provides environmental services within these systems. We studied the ant fauna in cattle farms at La Vieja river basin, Colombia, with the aim of analyzing the relations between tree cover and ant species diversity and composition in different land uses in this cattle-dominated landscape. Monitoring was performed between 2004 and 2007 in 21 plots representing seven contrasting land uses characteristic of this Andean landscape. Ants were sampled with baits (arboreal and ground) and pitfall traps. A total of 68,860 individuals belonging to 227 ant species was recorded. Ant diversity was positively related to the presence of woody vegetation. The largest number of ant species was found in secondary forests followed by improved pastures with trees. Pastures without trees had less than half the number of ant species in pastures with trees. Ant species richness in intensive Leucaena leucocephala (Mimosaceae) silvopastoral systems also surpassed that recorded in treeless pastures. This study provides evidence supporting the conservation value of silvopastoral systems at the landscape level in the Colombian Andes. The conservation of forest fragments in this area is vital, as they provide refuge for a unique regional ant fauna