Abstract

Background: Grassland restoration has gained significant attention as a climate change mitigation strategy through enhanced soil organic carbon (SOC) sequestration. Microbial residues, particularly necromass from bacterial and fungal communities, represent a crucial but understudied component of SOC formation in restored grasslands.
Objective: This study examines the mechanisms, temporal dynamics, and management implications of microbial residue contributions to SOC accumulation in restored grassland ecosystems over a 15-year chronosequence.
Methods: We analyzed microbial biomass, necromass, and SOC dynamics across 45 restored grassland sites in the Great Plains region, using biomarker analysis, stable isotope techniques, and advanced spectroscopic methods. Sites ranged from 1 to 15 years post-restoration, with native prairie and agricultural controls.
Results: Microbial residues contributed 35-65% of total SOC in restored grasslands, with fungal necromass accounting for 40-55% of microbial-derived carbon. SOC accumulation rates averaged 0.8 ± 0.2 Mg C ha⁻¹ yr⁻¹, with microbial contributions increasing from 35% in year 1 to 65% by year 15. Bacterial residues dominated early succession (years 1-5), while fungal contributions increased substantially after year 7. Management practices significantly influenced microbial residue accumulation, with diverse seed mixtures and reduced disturbance enhancing fungal necromass deposition.
Conclusions: Microbial residues represent the dominant pathway for SOC accumulation in restored grasslands, with temporal shifts from bacterial to fungal dominance reflecting ecosystem maturation. These findings have important implications for restoration management strategies aimed at maximizing carbon sequestration potential.