Acidobacteria Community Responses to Nitrogen Dose and Form in Chinese Fir Plantations in Southern China.

Acidobacteria is a new bacterial group, identified by molecular research, which is widely distributed and has specific ecological functions in forest soil. In this study, we investigated Acidobacteria response to N input, and the effects were related to N form and dose. The experimental design included two N forms (NH4+-N and NO3--N) and five levels of N deposition (0, 20, 40, 60, 80 kg N ha-1) for 2 years. Research into the Acidobacteria community was conducted using 16Sr RNA gene-based high-throughput pyrosequencing methods. Acidobacteria OTUs and N had a negative relationship in 0-60 kg ha-1 year-1; however, at N doses beyond a certain size, nitrogen might promote an increase in Acidobacteria OTUs. The Acidobacteria relative abundance under NH4+-N treatment was higher than under NO3--N treatment. Acidobacteria relative abundance decreased with increasing of NH4+-N dose, but increased with increasing NO3--N dose. Overall, 13 different Acidobacteria subgroups were identified, with Gp1, Gp2, and Gp3 being dominant. Significant differences in Acidobacteria distribution were primarily caused by N input and pH value. The environmental factors of N were all negatively related to Acidobacteria distribution in low N dose treatments (0-20 kg ha-1 year-1), but were positively related in response to N dose treatments (40-80 kg ha-1 year-1).