Abstract

Soil degradation disrupts microbial communities and their essential nutrient cycling functions, creating feedback loops that accelerate ecosystem decline. This study investigated microbiome-mediated nutrient cycling processes in degraded soils across a gradient of degradation severity, examining restoration potential through microbial inoculation strategies. We analyzed 180 soil samples from severely degraded (SD), moderately degraded (MD), slightly degraded (LD), and reference undisturbed (REF) sites using metagenomic sequencing, enzyme assays, and nutrient flux measurements. Results revealed that severe degradation reduced microbial diversity by 52% and functional gene abundance by 41%, with disproportionate losses in nitrogen fixation (68% reduction) and phosphorus solubilization (59% reduction) capacities. Network analysis identified critical breakdown in syntrophic interactions, particularly between nitrogen-fixing bacteria and mycorrhizal fungi. Microbial inoculation experiments restored 73% of nitrogen cycling capacity and 81% of phosphorus availability within 6 months, with consortia outperforming single-strain inoculants. Structural equation modeling demonstrated that microbial functional diversity explained 71% of nutrient cycling recovery. Key taxa including Azospirillum, Bacillus, and Penicillium emerged as restoration catalysts. These findings reveal that targeted microbiome manipulation can break degradation-poverty cycles, offering scalable solutions for degraded land restoration and sustainable agriculture in resource-limited environments.