Ants As Indicators of Land Use and Soil-Based Ecosystem Services in Agroecosystems of the Colombian Llanos.

Ants represent a widespread and functionally diverse taxonomic group that are both sensitive to land management and serve as important regulators of key soil processes.  Based on this knowledge, we sought to understand the impacts of recent changes in agricultural management on ant communities in the Orinoco River Basin of eastern Colombia and to develop bioindicators of soil-based ecosystem services in the region.  Ants were collected and identified (along with other soil macrofauna) from the soil and litter layer within 75 fields divided among five common agricultural land uses in the region: 1) annual crops (maize, soy and rice), 2) rubber plantations, 3) oil palm, 4) improved pastures (based on Brachiaria spp.), and 5) semi-natural savannas.  Within each of these fields a suite of soil and agroecosystem properties were measured and combined into synthetic indicators of five soil-based ecosystem services: 1) nutrient provision, 2) water storage and regulation, 3) maintenance of soil structure, 4) biodiversity conservation and 5) climate regulation services.  In total, 5154 individuals, comprised of 91 ant species, were collected.  Thirteen species were found to be significantly (P <0.05) associated with the five land uses, according to the IndVal method.  Meanwhile, fifteen species were identified as significant bioindicators for the provision of soil-based ecosystem services.  Our findings suggest that tree-based systems and less-disturbed pastures could contribute to biodiversity conservation and key ecosystem functions at the regional scale.  Additionally, the bioindicators developed here offer a valuable tool to help guide landscape transformations to better meet biological conservation objectives and enhance productivity and other key soil-based ecosystem services in this ecologically important and rapidly changing region of Colombia.