Long-term Miscanthus cultivation enhances soil quality in degraded acidic red soils: A multi-indicator assessment

Miscanthus has been widely recognized for marginal land restoration due to its high biomass productivity, strong environmental adaptability, versatile utilization pathways, and eco-friendly properties. However, a systematic and quantitative assessment of its long-term effects on soil quality under field conditions remains limited. This study quantitatively evaluated the 12 years remediation effects of two Miscanthus species (a hybrid named Xiangzamang and a Miscanthus floridulus germplasm) on degraded acidic red soils in southern China. Using 21 soil physicochemical and biological indicators, two minimum data sets (MDS1 and MDS2) were constructed, and linear (SL), non-linear (SNL) and membership function (MF) scoring models were applied to calculate the soil quality index (SQI). MDS2 proved the most robust selection method, though the choice of scoring model had a minimal effect on the final SQI results. Both Miscanthus species significantly enhance soil quality, with Xiangzamang exhibiting more comprehensive benefits, particularly in bulk soil improvement, achieving a 70% increase compared with C3 native grass mixture. Xiangzamang increased bulk soil SQI 1.7-fold (0–20 cm) and 1.5-fold (20–40 cm) compared with C3 native grass mixture, while M . floridulus achieved 1.4-fold and 1.1-fold enhancements, respectively. Soil organic carbon, mineral nitrogen, bulk density, and microbial biomass carbon were identified as the key indicators affecting SQI. Thus, future acidic red soil remediation strategies should prioritize these indicators. Moreover, these findings highlight the potential of Miscanthus , especially Xiangzamang, in marginal land improvement, and provide a scientific basis for sustainable ecological restoration in acidic red soil regions. • A soil quality index integrating phy-chemical and biological indicators was built. • SOC, MBC, N min and bulk density are key indicators for evaluating soil quality. • Long-term Miscanthus cultivation improves degraded acidic red soil quality. • The hybrid beat M. floridulus in enhancing soil quality, especially in bulk soil.