Effects of Elevation on Functional Genes of Soil Nitrogen Cycling in Beijing Platycladus orientalis Plantation

Objective Soil microbial mediated nitrogen cycling processes are the key biological factors that determine the emissions of greenhouse gases of N₂O in forest ecosystems. The aim was to reveal microbial nitrogen cycling processes and their driving factors for the reduction of greenhouse gas emissions in the forest.

Method By focusing on Platycladus orientalis plantation in the Ming Dynasty Tombs Forest Farm of Changping District in Beijing, this study applied the metagenomic method to investigate the microbial nitrogen cycling functional genes at different elevations (100 m, 300 m, and 500 m).

Result Elevation significantly influenced the β-diversity of the soil nitrogen cycling genes in the Platycladus orientalis plantation, which was mainly driven by the soil pH. The abundance of the gene encoding for the pathways of microbial nitrification, denitrification, ANRN, and DNRA were significantly enriched at the elevation of 100 m, and showed a significant positive correlation with the soil pH. The abundances of the genes nosZ, nirK, norB (denitrification), nrfA and nrfH (DNRA) were the highest at the elevation of 100 m, among which the pH significantly affected the relative abundances of the nirK, norB, nrfA and nrfH.

Conclusion This results reveal that pH is a key environmental factor driving the soil microbial-mediated nitrogen cycle in the Platycladus orientalis plantation, and the soil at low elevations has a higher abundance of functional genes related to the DNRA process, which is a key nitrogen cycling process of determining the production of N₂O.