Abstract

Pheidole fallax is one the most abundant ants in sites where coal mines have undergone rehabilitation and in forests without mine intervention. The impact that this species may have as an ecosystem engineer needs to be assessed. We aimed to test whether P. fallax nests have an effect on soil chemical properties, to characterize the organic debris found in the refuse piles, and to describe nest architecture as proxy of the bioturbation effect. The study was carried out in a coal mine in Colombia, in sites with 16 and 20 years of rehabilitation. Samples were taken from inside the nests, from the external refuse pile, and from a control treatment one meter away from the nest. The three sample types were subjected to chemical analysis and near-infrared spectra (NIRS). The biomass of items from the 20-year site was significantly greater, and P. fallax use food resources of different trophic levels, with arthropods and seeds being the main items in their diet. The NIRS analysis enabled us to distinguish the origin of the sample: refuse pile, interior of nest, or control soil. No statistical differences were found between the soil of the nests and control soil. High contents of organic matter and other parameters contributed to the soil nutrient pool through accumulation of organic debris in the refuse piles. Nest molds presented an asymmetric architecture, with mean volume ranging from 30 to 105.7 cm3 and an average of 11.8 chambers per nest. The construction and maintenance of nests may play an important role in the reestablishment of ecological and hydrological processes, such as bioturbation and water infiltration, respectively.