Background The construction of transmission towers in arid ecosystems has significantly disrupted ecological balance, triggering soil fertility degradation through altered microbial-mediated nutrient cycling. While vegetation restoration serves as a critical intervention for combating desertification and modulating soil microbial communities, its long-term impacts on microbial necromass carbon, a key determinant of soil organic carbon (SOC) persistence and ecosystem stability, remain poorly quantified.

Methods This study was carried out in the anthropogenic disturbance zone of the power transmission infrastructure within the Mu Us Sandy Land ecosystem. Standardized field sampling protocols coupled with gas chromatography-mass spectrometry (GC-MS) analytical techniques were implemented to evaluate the effects of engineered vegetation restoration on soil carbon. We employed amino sugar biomarkers to analyze microbial necromass dynamics in revegetated soils. By quantitative assessment of microbial residue carbon contributions to SOC, we established relationships between necromass carbon, soil properties, and microbial biomass using variance partitioning and Mantel tests.

Results 1) The results indicated that the microbial necromass carbon content (11.2 ± 0.1 mg/g) in vegetation restoration soil was significantly higher than that in disturbed soil (3.9 ± 0.6 mg/g), and restored to the level of undisturbed soil (8.84 ± 1.3 mg/g). 2) The contribution of microbial necromass carbon to soil organic carbon recovered from (21.9%± 3.1%) to (50.8% ± 4.0%), even higher than the undisturbed soil level of (30.0% ± 5.2%). 3) Soil microbial necromass carbon was mainly contributed by fungi, and the contribution of fungal residue carbon to soil organic carbon ranged from 18.3% to 29.8%, and that of bacterial residue carbon ranged from 13.6% to 20.9%. 4) The variance decomposition results showed that soil properties and microbial biomass jointly explained 48.3% of the variation in microbial necromass carbon content, in which soil properties explained 35.5% of the variation and microbial biomass explained 27.4% of the variation. Mantel analysis further showed that soil carbon and nitrogen content and microbial biomass carbon were significantly positively correlated with microbial necromass carbon content.

Conclusions Our findings demonstrate that vegetation restoration not only rehabilitates SOC pools but critically enhances their stability through fungal-dominated microbial necromass accumulation. This mechanistic understanding advances restoration strategies for arid land recovery by highlighting microbial-derived carbon as a fundamental indicator of soil health resilience.