Fig. 3.

Effect of the different treatments (CK, 0.5% NPs, and 5% NPs) in black and red soils on the metagenomic abundance and phylum-level composition of genes encoding the decomposition of aromatics and complex carbohydrates. a Changes in the relative abundance of genes involved in the degradation of aromatics and complex carbohydrates between control (CK), 0.5% NPs, and 5% NPs treatments after 30-day and 160-day incubations. The metagenomic abundance changes are indicated for both black and red soils in counts per million reads. Error bars denote standard deviation (n = 3). Different letters (a, b, c) indicate significant differences between the treatments (P < 0.05). b The treatment-specific relationships between CH₄ production and the abundance of genes encoding the degradation of aromatics (red lines) and complex carbohydrates (blue lines) after 160-day incubation. The metagenomic abundances are indicated as counts per million reads