Ant-mediated effects on soil nitrogen mineralization vary with species in a tropical forest

Ants as ecosystem engineers can modify soil heterogeneity and biochemical process, which regulates nitrogen mineralization dynamics. However, ant-mediated effects of different feeding-habits on nitrogen mineralization are not well documented, especially for underground-nesting ants in tropical forest soils. For this study, three dominant underground-nesting ant species with different feeding habits (i.e., honeydew-harvester Pheidole capellinii, predatory Odontoponera transversa, and saprophagous Pheidologeton affinis) were selected to identify their effects on nitrogen mineralization in a Xishuangbanna tropical forest. The results showed a higher average mineralization rate in nests of three ant species (0.88 mg kg(-1) d(-1)) compared with reference soils (0.36 mg kg(-1) d(-1)). The average nitrogen mineralization rates were 3.3 folds higher in P. capellinii nests than in reference soils, while those in nests of O. transversa and P. affinis were 2.3 and 1.8 folds, respectively. The change in nitrogen mineralization along soil profile varied with ant species. The greatest rates of nitrogen mineralization were observed in 10-15 cm layer of O. transversa and P. affinis nests, while those in P. capellinii nests were in 5-10 cm layer. The concentrations (87.4-269.6%) of carbon pools (i.e., microbial, readily oxidizable, and total organic carbon) and NH4+-N increased the greatest in nests of P. capellinii, whereas those (40.8-119.5%) of total, dissolved, and nitrate nitrogen were in nests of P. affinis. The shift in carbon pools was the most important factor that accelerated the nitrogen mineralization, followed by NH4+-N and total nitrogen. Our data indicated that nitrogen mineralization varied with ant species due to different modifications of feeding habits on soil variables in Xishuangbanna tropical forest.