Ants can exert a diverse effect on soil carbon and nitrogen pools in a Xishuangbanna tropical forest

Abstract

Ants are known as important ecosystem engineers for their potentials in modifying the energy flows and nutrient cycles of soil. However, the direction and degree of these modifications vary with ant species and inhabiting environments. In this study, three underground-nesting ants with different feeding-behaviors (Pheidole capellini - predominantly honeydew harvester, Pheidologeton affinis - scavenger, and Odontoponera transversa - predominantly predator) were employed to explore their effects on soil carbon (C) and nitrogen (N) pools in a Xishuangbanna tropical forest in southwestern China. We observed a pronounced effect of ants on components of soil C and N pools, and the effect varied with ant species. Microbial biomass carbon (MBC), total organic C (TOC), total nitrogen (TN) and NH4+ were higher in all ant nests than in the reference soils. However, readily oxidizable organic C (ROC) was only increased in Ph. Capellini and O. transversa nests, dissolved organic nitrogen (DON) in Ph. affinis and O. transversa nests, and NO3− in Ph. affinis nests. Ants significantly increased spatial variability of C and N pools with the higher values in deeper soil layers compared with reference soil. Pheidole capellini nests had the greatest increases of MBC (196.85%), TOC (86.82%) and ROC (68.64%) in 10–15 cm soil depth, whereas there were the highest increase of TN in 10–15 cm soil layer of O. transversa nests, DON in 5–10 cm soil layer of Ph. affinis nests, and NH4+ in 10–15 cm soil layer of Ph. capellini nests. The greatest increase of C pools (101.2 kg ha−1 TOC, 15.49 kg ha−1 MBC, and 4.89 kg ha−1 ROC) was found in Ph. capellini nests, while that of N pools (6380 g ha−1 TN, 110.44 g ha−1 DON, 128.88 g ha−1 NH4+ and 10.17 g ha−1 NO3−) was in Ph. affinis nests. We conclude that different feeding-behavior ants have a diverse contribution to soil carbon and nitrogen pools in the tropical forest.