Dynamics of Microbial Carbon Metabolism During Vegetation Restoration in Sandy Ecosystems

Understanding the succession of soil microbial carbon metabolism functions is crucial for elucidating carbon cycling mechanisms during ecosystem restoration in sandy lands. Soils were collected from Caragana korshinskii shrubland sites across a restoration chronosequence (0, 10, 30, 50, and 70 years) in the Mu Us Sandy Land. Biolog carbon source utilization analysis and metagenomic sequencing were employed to characterize the successional patterns of microbial carbon metabolism functions—a shift in carbon metabolism strategies from acquisition to conservation, and a transition in functional diversity from generalism to specialization. The results indicated that microbial communities exhibited two associated successional shifts in functional characteristics: carbon source utilization tended to transition from simple to complex substrates, while functional gene expression showed a progressive shift from broad multi-pathway patterns toward pathway-specific specialization. AWCD values increased continuously with restoration duration, and carbon source utilization patterns diverged significantly around 30 years. Early-stage sites (0–30 years) primarily utilized simple carbon sources, whereas late-stage sites (50–70 years) shifted toward more complex and diverse substrates. Principal component analysis revealed that 27 carbon sources contributed 91.3% of the variance to PC1. Microbial community structure succession revealed that Actinobacteria peaked at 10 years (43.63%), Proteobacteria peaked at 30 years (45.66%), and taxa such as Bacilli and Solirubrobacter dominated at 50–70 years. Carbon metabolism pathways exhibited stage-specific succession: glycolysis and the ED pathway were active in early stages, acetate metabolism dominated with the 3HB cycle peaking in intermediate stages, and the CBB cycle increased in later stages while methane metabolism shifted from high to low contribution. These two associated successional shifts occurred along the same restoration chronosequence, with the progressive transition in substrate utilization accompanying the development of specialist functional characteristics. These findings provide insights into the successional dynamics of microbial carbon metabolism during vegetation restoration, offering a microbiological basis for optimizing ecological restoration practices and enhancing soil carbon sequestration in sandy lands.