Soil Particle Size Distribution Characteristics of Mechanical and Water-Stable Aggregates in Alpine Meadows Under Different Grazing Intensities

Summary

This field-based study examined long-term natural grazing effects on soil structural stability in Qilian Mountain alpine meadows, using established grazing regimes rather than artificially controlled experiments. Light and moderate grazing maintained balanced soil structure with robust subsurface stability, whereas no grazing improved mechanical stability but compromised water stability, and heavy or extreme grazing caused severe aggregate degradation with enhanced subsurface fragility. The findings suggest moderate grazing optimises both soil structural resilience and sustainable grassland productivity in these alpine ecosystems.

Regional applicability

While the Qilian Mountains represent a distinct high-altitude ecosystem, the mechanistic findings regarding grazing intensity, soil aggregate dynamics, and the balance between biological cementation and physical disturbance may have limited direct applicability to UK lowland and upland grasslands, which differ substantially in climate, soil type, vegetation composition, and management history. UK pasture researchers might adapt the methodological approach of assessing long-term natural grazing regimes rather than short-term experimental manipulations, though optimal grazing intensity thresholds would likely differ.

Key measures

Particle size distribution of mechanical and water-stable soil aggregates; aggregate stability indices; soil properties; root biomass; nitrogen forms; microbial biomass; soil mineralization rates

Outcomes reported

The study measured particle size distribution and mechanical and water-stable soil aggregate stability across different soil depths under five grazing intensity regimes (no grazing, light, moderate, heavy, and extreme grazing) in alpine meadows of the Qilian Mountains. Environmental factors including elevation, soil properties, root biomass, nitrogen forms, microbial biomass, and mineralization were analysed as co-regulators of aggregate stability.

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