Microbial inoculation drives alpine compost maturity by overcoming thermodynamic barriers and reshaping fungal networks

The cold environment of the Qinghai-Tibet Plateau imposes a severe "thermodynamic startup barrier" on organic waste composting. To elucidate the bioaugmentation mechanisms overcoming this constraint, this study evaluated a control (CK), two single inoculants (DY, MM), and two composite inoculants (EM, FH) during cattle and sheep manure composting. Results demonstrated that the specialized composite inoculant (FH) generated an initial net heat surplus (98.80 kJ/kg) and rapidly elevated the effective cumulative temperature to >1050 C-day. This thermodynamic remodeling accelerated organic matter mineralization and eliminated phytotoxicity, achieving a Seed Germination Index (GI) of 111.87% and significantly reducing the E4/E6 ratio (2.31) for enhanced humification. High-throughput sequencing revealed that this inoculation-induced thermal dynamic exerted strong environmental filtering. Specifically, it directionally enriched heat-tolerant, lignocellulose-degrading fungi, increasing the relative abundance of the phylum Ascomycota to 74.43% (particularly the genera Phialophora and Schizothecium). Topological analysis showed that FH transformed loose microbial assemblies into robust, positively synergistic networks, increasing the fungal network average degree from 4.42 (CK) to 13.42. Crucially, Structural Equation Modeling (SEM) and functional predictions clarified the underlying biological pathways. Rather than merely altering general diversity, FH intervention triggered a specific cascade: initial thermal accumulation selected for saprophytic fungi that subsequently dominated carbon transformation and humification processes. This fungi-driven pathway exhibited the highest total effect (0.59) on compost maturity. Overall, securing an initial thermal surplus via composite inoculants triggers environmental filtering, which reshapes a resilient, fungi-centric ecological network capable of deep organic matter bioconversion under alpine constraints.