Spatial Patterns and Composition Traits of Soil Microbial Nitrogen-Metabolism Genes in the Robinia pseudoacacia Forests at a Regional Scale

Abstract

Microbial-driven processes related to the nitrogen-metabolism (N-metabolism) in soil are critical for ecosystem functioning and stability. There are spatial patterns of microbial-mediated nitrogen processes, but we still lack an overview of the soil N-metabolism genes of single nitrogen-fixing tree species pure forests at a regional scale. Here, we investigated the spatial variation and drivers of microbial N-metabolism genes in the rhizosphere soil of Robinia pseudoacacia on the Loess Plateau by metagenomic technology. We found that the distance-decay of soil N functional gene similarities in Robinia pseudoacacia forests on the Loess Plateau spanning a geographic distance of 230 km was significant (p < 0.001). The gene composition and co-occurrence patterns in the process of soil microbial N-metabolism were very different, and they were mainly driven by soil pH and MAP (mean annual precipitation). The proportion of positive links and edges co-occurrence networks between N functional genes increased with increasing pH, suggesting that increasing pH promoted connections between functional genes. The relative frequencies of N-metabolism pathways were consistent on the Loess Plateau, the abundance of ammonia assimilation pathway was highest, and the abundance of the nitrogen fixation pathway was the lowest; only the abundance of the nitrogen fixation pathway was not significantly different. The bacterial and archaeal communities involved in soil nitrogen metabolism were significantly different. Structural equation modeling showed that decreases in soil pH and MAP mainly affected the increase in nitrogen functional gene abundance through an increase in the diversity of N-metabolism microorganisms. In conclusion, this study provides a baseline for biogeographic studies of soil microbe functional genes.

Mixed plantation forest litter improves microbial nitrogen transformation by increasing nitrogen metabolism related genes and key bacterial taxa in northern China

“…Microbial‐driven N metabolism in the soil is vital for sustaining forest ecosystem functioning and stability (Ku et al, 2022). The TN content in MCBP litter was higher than that in both BP and CP litters (Figure 1a), which was because of the highly diverse substrate and nutritional composition (Jia et al, 2021; Liu et al, 2023).…”

“…This enhancement was attributable to the similarity in microbial community composition and the role of functional microbes (Wang et al, 2021). Due to the similar litter substrate of BP and CP forests, resulting in the microbial community composition and a stronger association between N metabolism‐related enzymes and genes (Ku et al, 2022). The results showed that the substrate composition of pure litter (CP forest or BP forest) was a little different, and the microbial community structure was similar, reducing the consistency between functional enzymes and genes (Ding et al, 2023).…”