Synergistic effects of organic amendments on soil properties and microbial communities in alpine mining soils

Mining activities on the Qinghai-Tibet Plateau have severely degraded soil structure, reduced nutrient availability, and disrupted soil biota, posing major challenges for ecological restoration in alpine environments. While organic amendments are widely recognized as effective strategies for soil improvement, their synergistic effects on soil physicochemical properties, heavy metal dynamics, and microbially mediated ecological processes remain insufficiently understood. In this study, we conducted a field experiment using reconstructed serpentine-loess substrates to evaluate the effects of humic acid, sheep manure, and structural organic materials (grass fiber) on soil properties and microbial functioning. Our results show that humic acid primarily improved soil aggregation and water retention, while sheep manure enhanced nutrient availability and copiotrophic microbial taxa. Structural organic materials promoted macropore formation and root development. Combined amendment treatments significantly improved vegetation establishment and reduced Cu and Hg concentrations while stabilizing Cr and Zn in soil.