Soil Bacterial Community Response to Short-Term Manipulation of the Nitrogen Deposition Form and Dose in a Chinese Fir Plantation in Southern China
2016
Liu, Caixia | Dong, Yuhong | Sun, Qiwu | Jiao, Ruzhen
The changes of soil bacterial biomass and community composition were monitored in a simulated nitrogen (N) deposition experiment during 4 years of Cunninghamia lanceolata growth in a plantation site in southern China. The experimental design included two N forms (NH₄Cl and KNO₃) and five levels of N deposition (0, 20, 40, 60, 80 kg N ha⁻¹) for 2 years. Research into the bacterial population was conducted using plate count, phospholipid fatty acid (PLFA) composition, and 16Sr DNA gene-based high-throughput pyrosequencing methods. The results of plate count and PLFA analysis indicated that ammonium (NH₄⁺) addition increased bacterial number and biomass, whereas nitrate (NO₃⁻) addition decreased these values. The high-throughput sequencing showed that N deposition of the two N forms inhibited the growth of bacteria compared with control plots, and the changing trend was related to the NH₄⁺-N/NO₃⁻-N ratio of soil. When the N deposition dose exceeded 20 kg N ha⁻¹, there was a significant effect on cultured bacteria counts and bacterial biomass. When examining the bacterial community, we observed 22 bacterial phyla of which Proteobacteria, Acidobacteria, and Actinobacteria were dominant. Acidobacteria abundance was higher in NH₄⁺ treatments than NO₃⁻ treatments. When the rates of NH₄⁺ deposition increased, Acidobacteria abundance decreased; however, it showed a positive correlation in NO₃⁻ treatments. The bacterial cluster structures were significantly different between different N addition rates in the NO₃⁻-treated plots. This research will provide data support to addressing the negative influences of nitrogen deposition and provide reference for soil management.
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