Molecular Soil Biology 2026, Vol.17, No.1, 38-50 http://bioscipublisher.com/index.php/msb 43 management practices (Zhang et al., 2025). Co-occurrence network analyses reveal that bacterial network complexity decreases over time whereas fungal networks may partially recover or become more modular, suggesting differential adaptability among microbial groups to continuous cropping stress (Chen et al., 2025; Wang et al., 2025). These variations underscore the importance of monitoring specific microbial taxa to understand soil health trajectories under intensive greenhouse cucumber production. 5 Driving Factors of Changes in Soil Microbial Communities 5.1 Regulatory effects of root exudates on microbial communities Root exudates play a crucial role in shaping soil microbial communities by providing carbon sources and signaling molecules that selectively stimulate or inhibit specific microbial taxa. These exudates include sugars, amino acids, organic acids, and secondary metabolites that influence microbial growth and activity in the rhizosphere, thereby affecting community composition and function. The diversity and quantity of root exudates can vary with plant species, developmental stage, and environmental conditions, leading to dynamic shifts in microbial populations around cucumber roots under continuous cropping (Philippot et al., 2023). Such selective pressures can promote beneficial microbes involved in nutrient cycling or suppress pathogens, but continuous monoculture may alter exudate profiles unfavorably, reducing microbial diversity and increasing pathogen prevalence. Moreover, root exudates contribute to feedback loops that modify soil properties and microbial habitats. Microbial metabolism of exudates can change soil pH, nutrient availability, and organic matter content locally, which further influences microbial community assembly and interactions (Philippot et al., 2023). These microbially mediated modifications create heterogeneous niches that support diverse microbial functions essential for plant health. However, under continuous cucumber cropping, altered exudation patterns combined with soil degradation may disrupt these feedbacks, leading to simplified microbial networks and impaired ecosystem services. 5.2 Effects of fertilization and agronomic management practices Fertilization regimes and agronomic practices significantly impact soil microbial community structure by altering nutrient availability and soil physicochemical conditions. Organic amendments generally enhance microbial diversity and functional gene abundance by supplying complex carbon substrates that support diverse heterotrophic microbes (Zheng et al., 2019). In contrast, excessive use of chemical fertilizers can reduce microbial richness by favoring fast-growing copiotrophic bacteria while suppressing oligotrophic taxa adapted to low-nutrient environments. The balance between these inputs influences the abundance of key functional groups involved in nitrogen cycling, carbon turnover, and disease suppression. Agronomic practices such as crop rotation, tillage intensity, and irrigation also modulate microbial communities by affecting soil moisture regimes, aeration, and root-soil interactions. For example, crop rotation introduces varied root exudates and residues that maintain higher microbial diversity compared to continuous monocropping (Figure 3) (Li et al., 2022; Bai et al., 2023). Reduced tillage preserves soil structure and fungal hyphal networks critical for nutrient transport. Together, these management factors interact with fertilization to shape the resilience and multifunctionality of soil microbiomes under greenhouse cucumber cultivation. 5.3 Influence of soil environmental factors Soil environmental factors including pH, organic matter content (SOM), moisture levels, and nutrient status are primary drivers of soil microbial community composition and diversity. Soil pH strongly influences bacterial diversity by affecting enzyme activities and nutrient solubility; many bacterial taxa have narrow pH optima leading to shifts in dominant phyla as pH changes (Zhou et al., 2020). Fungal communities tend to be less sensitive to pH but respond more to organic matter quality and moisture availability. High SOM supports greater microbial biomass and functional potential by providing energy sources for heterotrophs (Zheng et al., 2019; Huang et al., 2024).
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