Landslide and aspect effects on artificial soil organic carbon fractions and the carbon pool management index on road-cut slopes in an alpine region

Roadway rock-cut slopes have a strong effect on soil organic carbon (SOC), its fractions and overall soil health. However, it is still unknown how SOC fraction properties are influenced under different aspect conditions. We quantified differences in artificial SOC fractions, soil nutrients, and enzyme activities across eight types of roadway rock-cut slopes in Songpan, China. On slopes in landslide areas, four aspects (S, W, N, E) were selected for study, and four equivalent aspects on slopes not affected by a landslide were selected as a reference. SOC, easily oxidizable organic carbon (EOC), particulate organic carbon (POC), urease, sucrase, total nitrogen (TN), and carbon pool management index (CPMI) significantly differed among non-landslide aspects, however, except for POC and urease, did not differ with aspect on landslide-affected slopes. In contrast, dissolved organic carbon (DOC), nitrate nitrogen (NO3–-N), and ammonia nitrogen (NH4+-N) significantly differed among aspects on landslide-affected slopes, while they did not significantly differ on aspects of non-landslide slopes. However, higher SOC, EOC, POC, TN, urease, sucrase, and CPMI occurred on non-landslide slopes than landslide-affected slopes of the same aspect, suggesting that landslide slopes may face serious degradation. Our findings indicate that slope aspect and the occurrence of landslides have an influence on SOC pools, and consequently on CPMI.