Study on the relationship between soil aggregate size, electrical conductivity, organic carbon, and nutrient availability in highway slopes in alpine regions

This study investigated the soil aggregate distribution on highway slopes in the alpine region of western Sichuan, China. The proportion of >5 mm aggregates was significantly higher than that of other size fractions (P < 0.05), whereas the content of 0.25-0.5 mm aggregates was the lowest. Across all aggregate size fractions, the contents of available nitrogen (AN), available phosphorus (AP), and available potassium (AK) were analyzed. Overall, the available nutrient contents in soil aggregates were relatively high at elevations of 3321 m and 3677 m, with AN and AP contents gradually decreasing as aggregate size increased. Further calculations revealed that the nutrient contribution rate of >5 mm aggregates was significantly higher than that of other size fractions (P < 0.05). This study also indicates that soil organic carbon (SOC) has a significant positive correlation with AP, and soil electrical conductivity (SEC) has a significant positive correlation with AN, AP, and AK. These findings provide new insights into the storage of available nutrients in highway slope soils in alpine regions and offer a theoretical basis for improving roadside ecosystems.