In arid sandy plantations, stand density critically regulates belowground ecosystems, yet its effects on microbial network complexity, stability, and function are not fully understood. This study examined Pinus sylvestris var. mongholica plantations along a density gradient (Very high density (VHD): 2,450 trees ha ⁻¹ , High density (HD): 1,633 trees ha ⁻¹ , Moderate density (MD): 1,067 trees ha ⁻¹ , Low density (LD): 583 trees ha ⁻¹ ) at two soil depths (0–20, 20–40 cm) in the Otingdag Sandy Land, integrating soil physicochemical, enzymatic, and microbial network analyses. Key findings were: (1) Soil organic carbon, total nitrogen, key enzyme activities [urease (URE), acid phosphatase (PHO), and nitrate reductase (NR)], and ecosystem multifunctionality showed a unimodal response, peaking at medium densities. (2) Microbial responses diverged: bacterial α-diversity changed but composition remained stable, whereas fungal composition was highly density-sensitive. Mid- to low densities promoted more complex, modular, and stable microbial networks. Mantel tests identified pH, URE, and Ammonium nitrogen (NH₄ ⁺ -N, AN) as key drivers for bacterial phyla, and pH, Soil organic carbon (SOC), Total nitrogen (TN), PHO, and Polyphenol oxidase (PPO) for differentiating Ascomycota and Basidiomycota. (3) Random Forest regression identified microbial network stability as the top predictor of multifunctionality, surpassing diversity. Partial Least Squares Path Modeling (PLS-PM) analysis revealed that stand density enhances multifunctionality primarily by improving the soil environment, with microbial networks acting as environment-dependent regulators. This study demonstrates that moderate stand densities optimize microbial network resilience and ecosystem multifunctionality in sandy plantations, providing a novel perspective from microbial network stability.

Desertification is an ever-growing global ecological and environmental problem. With the implementation of various ecological restoration initiatives, vegetation cover in many desert regions has increased substantially. Consequently, it is essential to understand the dynamics of ecosystem services (ESs) in desert ecosystems to better inform environmental management. This study integrates the InVEST model, RWEQ model, Spearman correlation analysis, trade-off and synergy coefficient method, and the Partial Least Squares Path Model (PLS-PM) to systematically assess the spatio-temporal dynamics and underlying driving mechanisms of five key ESs in the Kubuqi (KBQ) Desert, northern China. Specifically, the application of PLS-PM enables the identification of latent pathways, indirect effects, and multi-step causal relationships, which traditional correlation-based methods fail to capture. The results show that the KBQ Desert underwent substantial land use changes from 2000 to 2020: sandy land decreased by 2697.83 km², grassland increased by 1864.15 km², and cropland and urban land expanded by 519.15 km² and 257.74 km², respectively. ESs exhibited divergent trajectories. habitat quality (HQ), carbon sequestration (CS), soil conservation (SC), and water yield (WY) all showed overall increases, with WY and SC increasing particularly strongly, whereas Sand-fixation service (G) displayed a fluctuating trend. Over the past two decades, HQ–CS, HQ–G, and CS–G have shown moderately strong synergies, while CS–WY has exhibited a pronounced trade-off, and SC–G and SC–CS have displayed relatively weaker trade-offs. The spatial distribution results of trade-off and synergy relationships show that the KBQ Desert is dominated by a synergy relationship, and the main synergy relationship combinations are CS–HQ, CS–SC, and HQ–SC. The correlation coefficients between other ES pairs are generally low. Additionally, this study identifies key pathways through the PLS-PM method, such as PRE → NDVI → ES and LU → NDVI → ES, revealing the complex interactions between precipitation (PRE), land use (LU), and vegetation dynamics. The findings show that land use (LU) consistently exerts a strong negative impact on CS, while PRE and NDVI have a significant positive effect on WY. These pathways deepen our understanding of how climate and anthropogenic factors affect ESs, particularly the influence of temperature (TEMP) on evapotranspiration (ETP), which in turn affects WY. Additionally, the impact of NDVI on wind–sand fixation (G) and SC varies over time, with vegetation dynamics playing a particularly enhanced role in 2010 and 2015. These findings highlight the impact of ecological restoration and land management on regional ESs changes. A comprehensive understanding of the interactions between climate factors, LU, and vegetation dynamics will help in developing more effective intervention strategies.

Wetlands act as essential global carbon sinks. In high-latitude cold-arid regions, soil carbon sequestration and SOC fraction stabilization may be uniquely regulated by regional conditions; however, carbon sequestration characteristics can vary substantially among wetland types. This study assessed the distribution of soil organic carbon (SOC) fractions and their controlling factors in four representative wetland types: riverine (RW), lacustrine (LW), artificial (AW), and marsh (MW). Topsoil (0–20 cm) and subsoil (40–60 cm) samples were analyzed for SOC and its fractions (particulate organic carbon, POC; mineral-associated organic carbon, MAOC), along with their associations with biotic and abiotic drivers. A significant interaction between wetland type and soil depth was observed,. In topsoil, MW had the highest POC and SOC contents (13.9 and 15.5 mg g ^- ¹), whereas RW and LW subsoils showed the highest soil carbon accumulation, with POC and SOC contents of 22.9.5-24.7 and 18.5-19.5 mg g ^- ¹, respectively. Furthermore, linear mixed-effects models (LMM) revealed divergent stabilization pathways: POC accumulation was primarily predicted by biogeochemical factors, with total nitrogen (TN) as the dominant positive driver (R ^2m = 0.75). In contrast, MAOC accumulation was controlled by soil hydrology and the redox state, showing a strong negative correlation with saturated hydraulic conductivity (Ks, R ^2m = 0.36). These findings elucidate type- and depth-specific SOC partitioning mechanisms, contributing to the knowledge for enhanced soil carbon management and ecological conservation in Yellow River wetlands.

Mixed plantations of Pinus sylvestris var. mongolica with native shrubs are widely established in semiarid sandy landscapes, yet soil microbial responses may differ among mixed-planting modes depending on the companion shrub species. We compared soil bacterial and fungal communities across three approximately 9-year-old mixed-planting modes in the Mu Us Sandy Land, where P. sylvestris var. mongolica was combined with Juniperus sabina (Ps–Js), Salix psammophila (Ps–Sp), or Corethrodendron fruticosum (Ps–Cf). Planting configuration was associated with shifts in soil physicochemical conditions. Bacterial α-diversity did not differ among modes, whereas fungal α-diversity was higher in Ps–Sp. Community composition diverged across modes for both domains, and LEfSe identified configuration-specific taxa. Null-model analyses showed that bacterial assembly was consistently dominated by stochastic components, whereas the relative contributions of fungal assembly processes varied among mixed-planting modes. Functional inference further suggested mode-associated differences in fungal trophic guild composition, with Ps–Cf showing significantly higher ectomycorrhizal abundance and Ps–Sp showing higher representation of saprotroph-associated guilds; by contrast, predicted bacterial functional profiles were broadly comparable among modes. Together, these results indicate that bacterial and fungal communities showed different response patterns among mixed-planting modes: bacterial communities showed compositional differentiation but little variation in α-diversity and consistently stochastic assembly, whereas fungal communities showed mode-related changes in α-diversity, the relative contributions of assembly processes, and trophic guild composition. These findings provide a microbial basis for considering shrub-species selection when designing P. sylvestris var. mongolica mixed plantations in semiarid sandy ecosystems.