Integrative analysis of soil-microbe-metabolite interactions in urban forests

Urban forests, are essential components of urban ecological infrastructure and play a vital role in providing various ecosystem services. However, the long-term stability of these services is threatened by a limited understanding of the complex interactions among soil properties, microbial communities, and rhizosphere metabolites. This study aimed to elucidate the variations in soil factors, microbial communities, and rhizosphere metabolites across different forest stands and seasons within urban ecosystems and to identify the key regulators of metabolite accumulation. This study was conducted in the Zhuyu Bay Scenic Area in Yangzhou, Jiangsu, China and involved six distinct forest stands: mixed pine and cypress forest, Metasequoia glyptostroboides, Cornus officinalis, mixed broad-leaved shrub forest, mixed broad-leaved tree forest, and bamboo forest. Seasonal and stand-specific differences were observed in the soil properties, microbial communities, and rhizosphere metabolites. Actinobacteria (bacteria) and Ascomycota (fungi) exhibited significant differences among the forest stands, with lipids and lipid-like molecules, organic oxygen compounds, and organic acids and their derivatives being the most abundant metabolites. Partial least squares path model analysis indicated that among the various factors, soil physicochemical properties had the most significant impact on metabolite composition (0.617). In terms of microbial communities, bacterial diversity positively influenced metabolite composition (0.037), whereas fungal composition had the most substantial negative impact (−0.090). Correlation analysis further revealed that naringenin 1, a crucial intermediate in flavonoid synthesis, was positively correlated with Poribacteria, suggesting that Poribacteria play a key driver in flavonoid accumulation. These findings have significant practical implications. This study provides scientific support for optimizing urban forest management by highlighting the importance of maintaining healthy soil. Identifying key microbial groups and metabolites offers targets for enhancing the ecological functions of urban forests, including carbon sequestration and pollutant degradation. Moreover, this study addresses a research gap regarding the dynamics of bulk soil and rhizosphere metabolites in urban forests, paving the way for future research into ecosystem stability and sustainable urban development.