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).