Soil C:N:P stoichiometry and microbial community dynamics across six vegetation restoration patterns in the upper...

The upper Yellow River is a crucial ecological barrier and water conservation zone in the Yellow River Basin. Since 2000, extensive afforestation in this region has markedly improved the carbon sequestration capacity. Nevertheless, the responses of soil C:N:P stoichiometry and microbial diversity to different vegetation restoration patterns remain insufficiently understood. This study was conducted at a representative restoration site (Erlang Mountain) in the upper Yellow River. Abandoned farmland (Af, abandoned for more than three years) was used as the background, and six types of plantations with a uniform recovery period of 20 years were selected: mixed forest (Mf), Hippophae rhamnoides (Hr), Picea crassifolia (Pc), Prunus sibirica (Ps), Larix gmelinii (Lg), and Pinus tabuliformis (Pt). These tree species are widely used for afforestation in the upper Yellow River region and represent the dominant vegetation restoration strategies. Using 16S rRNA and ITS amplicon sequencing, this study clarified the mechanisms underlying soil microbial diversity and C:N:P stoichiometry across these restoration types. The results revealed the following. (1) Soil C (SOC) and N (TN) contents and stocks were the highest in Mf but the lowest in Hr (P < 0.05). Except for Mf, the soil C and N contents and stocks in the Lg forests exceeded those in the other stands (P < 0.05), whereasthe soil P (TP) in Pt was the lowest (P < 0.05). (2) The soil bacterial α-diversity in Mf and Lg was greater than that in other afforestation lands (P < 0.05), with Mf exhibiting the highest α-diversity, dominated by Acidobacteriota and Pyrinomonadaceae. The soil fungal α-diversity in Cl exceeded that of the other land use types (P < 0.05). The abundance of Acidobacteriota in Hr soils was lower than that in other forests, whereas the abundances of Ascomycota and Mortierellaceae were higher. (3) Precipitation exerted a negative effect on soil C:N:P stoichiometry but a positive effect on bacterial α-diversity (P < 0.05). pRDA analysis indicated that the vegetation restoration type significantly influenced soil C:N:P stoichiometry and microbial diversity (P < 0.05). This study demonstrated that vegetation restoration reshaping microbial community composition and improving soil C and N contents, with Mf and Lg exerting a stronger effect than other vegetation restoration types, thereby providing insights into rational afforestation in these regions.