Metagenomics reveals soil nitrogen cycling after vegetation restoration: Influence of different vegetation restoration strategies

Microorganisms play a crucial role in the cycling and transformation of nitrogen (N) within ecosystems. However, there is limited understanding regarding the impact of vegetation restoration on soil N cycling. A field study investigated the effects of different vegetation restoration strategies on soil microbial N cycling in sandy deserts of northern China including the use of metagenomic sequencing technology. The restoration strategies included the planting of Bromus inermis Leyss (SB), Medicago sativa L. (AF), and combined planting of Salix babylonica L. and Bromus inermis Leyss (FG). Compared with the natural restoration (CK), the abundance of genes related to soil N nitrification and denitrification processes was found to be higher in the AF and SB restoration strategies. On the other hand, the SB strategy specifically led to an enrichment of genes linked to dissimilatory nitrate reduction to ammonium (DNRA). Compared with the CK, the abundance of amoC/pmoC, hao and nxrA involved in soil N nitrification were higher in AF. The diversity of the fungal community was more strongly influenced by various vegetation restoration strategies compared to bacteria. Interestingly, FG had no significant effect on bacterial and fungal diversity compared to CK. However, alpha diversity of fungal communities was lower in AF and higher in SB compared to the CK. Soil pH was positively related to functional genes that drive nitrification and denitrification processes (nirK, amoC/pmoC, and hao). N fixation and DNRA exhibited a negative correlation with both microbial biomass carbon and microbial biomass nitrogen. Consequently, the planting of AF and SB hold significant importance in promoting soil N cycling within degraded lands. The study offered valuable insights into the microbial functional potentials associated with long-term vegetation restoration efforts, potentially bearing significant implications for soil N cycling in the degraded lands of northern China.