Shrub planting in the desert steppes of arid northwest China is a common ecological management strategy to combat desertification. However, the mechanisms by which planted shrubs influence plant-soil-microbe interactions and regulate soil respiration remain poorly understood. Therefore, the study focused on the issues in the planted shrub ecosystem in Yanchi county, Ningxia province, and the experiments were conducted along the horizontal gradient of the shrub root zone (shrub zone, transition zone from shrub to grass, and grassland zone) based on the theory of shrub fertile island effects. Meanwhile, variance analysis, redundancy analysis, and correlation analysis were used to investigate the impacts of planted shrubs on plant-soil-microbe interactions and to analyze the microbial-driven mechanisms of soil respiration. The results showed that: (1) Both soil nutrients and microbial biomass decreased with increasing soil depth. The average total microbial biomass in the 0-50 cm soil layer ranged from 13.8 to 29.2 nmol/g. Bacteria dominated the microbial community, with Gram-positive bacteria accounting for 38.5%-39.6% and Gram-negative bacteria accounting for 26.5%-34.3%. This demonstrates that shrubs maintain microbial stability in surface soils, where nutrient cycling and organic matter turnover are most intense. (2) Planted shrubs significantly increased the ratio of Gram-positive to Gram-negative bacteria, facilitating the transformation of soil bacterial nutritional strategies from an "oligotrophic type" in the grassland zone to an "eutrophic type" in the shrub zone, thereby enhancing the availability of organic carbon. Such transitions indicate that shrubs create a nutrient-enriched microenvironment that accelerates decomposition and improves soil fertility. (3) Soil respiration, soil temperature, and soil water content exhibited a "single-peak" curve during both the growing season and at daily dynamics. Soil respiration was significantly positively correlated with soil water content but not significantly correlated with soil temperature. This suggests that in arid desert steppe ecosystems, soil moisture rather than thermal conditions is the major driver of soil carbon release, underscoring the sensitivity of these systems to precipitation events. (4) Shrub planting significantly improved the soil microenvironment, while soil organic carbon, soil water content, and β-D-Glucosidase activity contributed most significantly to microbial community composition. The increase in microbial biomass effectively promoted soil respiration. Overall, planted shrub establishment enhances soil quality, strengthens plant-soil-microbe feedbacks, and builds resilience of ecosystems against land degradation. These findings not only provide a theoretical basis and empirical data for understanding the functioning of shrub ecosystems, but also offer practical implications for carbon management and ecological restoration in arid and semiarid regions worldwide.