Objective The adaptive mechanisms underlying plant root nutrient acquisition strategies in fragile ecosystems represent a central topic in ecological research. The synergistic regulation of planting patterns and arbuscular mycorrhizal fungi (AMF) is widely recognized as a key pathway to enhance plant stress resistance and ecosystem function. However, the coupled mechanisms by which these two factors drive rhizosphere microenvironments and root morphology remain insufficiently understood. To elucidate how planting patterns and AMF synergistically shape the coupling between rhizosphere processes and root architecture, this study aims to reveal the coordinated regulatory effects of different planting patterns and AMF inoculation on rhizosphere dynamics and root system configuration.

Method This study was conducted from 2022 to 2023 in the typical Pisha sandstone area of Jungar Banner, Ordos City, Inner Mongolia of northern China, focusing on stress-tolerant shrub species native to the region. The experiment included three planting patterns: monoculture of Clematis fruticosa and Spiraea pubescens, respectively, and a mixed-culture treatment of both shrubs combined with AMF inoculation and non-inoculation treatments. We systematically analyzed variations in rhizosphere soil microhabitats and fine root morphological traits. Two-way analysis of variance (ANOVA) was employed to test treatment effects, while partial least squares path modeling (PLS-PM) was used to dissect the driving effects of rhizosphere microenvironment on root morphology.

Result The results demonstrated that significant interactive effects existed between planting patterns and AMF inoculation on the rhizosphere microenvironment and root morphology. Under monoculture combined with AMF inoculation, the contents of microbial biomass carbon and nitrogen in the rhizosphere of Clematis fruticosa increased significantly by 120.7% and 337.2%, respectively compared with the mixed-culture inoculation treatment (P < 0.05). Meanwhile, AMF inoculation reduced nitrogen hydrolase activity under monoculture and mixed-culture treatments by 31.7% and 41.6%, respectively compared with non-inoculation controls (P < 0.05). In contrast, mixed-culture enhanced soil available nitrogen content for both C. fruticosa and S. pubescens through interspecific nutrient complementarity, and synergized with AMF to decrease rhizosphere pH of the two shrubs by 0.3 and 0.1 units, respectively. Under monoculture, AMF inoculation significantly increased average root diameter of C. fruticosa and S. pubescens by 16.7% and 20.0%, respectively compared with non-inoculated controls. Without AMF inoculation, the number of root tips for both shrubs under monoculture increased significantly by 95.1% and 59.2%, respectively compared with mixed-culture treatments. Partial least squares path modeling (PLS-PM) analysis revealed that soil enzyme activity (total effect + 0.894) and pH (total effect + 0.548) were the core drivers of changes in root morphology.

Conclusion By integrating multi-parameter datasets, this study demonstrates that shrub root architectural formation in the Pisha sandstone region is predicated on mycorrhizal symbiosis and mediated by remodeling of rhizosphere enzyme activity and pH. This plasticity reflects a differentiated adaptive strategy to planting patterns and inoculation treatments, offering a scientific foundation for optimizing plant-microbe resource allocation in vegetation restoration.