Soil aggregate stability and erodibility are the influential factors governing soil resistance to water erosion. The interactions among aggregate stability, erodibility, and their influencing factors have not been fully explored. We collected soil samples from 0–10 cm and 10–20 cm layers in the Zhifanggou watershed. Then, the major contributors to aggregate stability and erodibility and how soil properties, environmental factors and land use contributed to them were explored by using partial least-squares regression and path analysis, respectively. The results showed that the major contributors included the slope, soil organic carbon (SOC), elevation, the percentage of landscape area of farmland (PLAND_F) and grassland (PLAND_G), the land surface temperature difference between seasons (ΔLST), topographic wetness index (TWI), pH, amorphous iron (poorly ordered forms of iron, Fe_o), and calcium carbonate (CaCO₃). In which, the slope, SOC, and elevation were the most important contributors to the mean weight diameter (MWD) and the percentage of water-stable aggregates greater than 0.25 mm (WSA_>0.25) and had a direct contribution to MWD, WSA_>0.25, and K factors. The PLAND_F and PLAND_G had a significant and indirect contribution to those three indices by affecting slope. Meanwhile, the effects of pH, Fe_o, and CaCO₃ on WSA_>0.25 should also not be underestimated. For MWD and WSA_>0.25, there was a significantly higher effect of the land use types and composition than hydrothermal conditions. For K factors, PLAND’s contribution was still higher than ΔLST and TWI, but they were all significant. The other soil properties, including pH, CaCO₃, and Fe_o, indirectly affected them by influencing SOC. However, the direct contributions of soil properties increased as the soil layer deepened.

Root tensile strength (T_r) is a fundamental root mechanical trait and serves as a key parameter for assessing the contribution of vegetation to slope stability. T_r is known to exhibit high intraspecific variability, but whether T_r varies with season remains unclear. Here, we investigated the seasonal variation in T_r in two commonly seen herbaceous species, i.e., Artemisia argyi and Cirsium setosum, both of which can be future candidates for revegetating species along roadsides in temperate and subtropical regions. We examined the T_r of their first- (closest to the stem base) and third-order lateral roots sampled in the southwest of Henan, China, in two distinct periods: September (late growing season) and December (dormant season). We found that the T_r of the thicker, first-order roots in September was significantly greater than that in December. However, such seasonal variation was not found for the thinner third-order roots. When fitting the relationship between T_r and root diameter using a two-parameter power law equation, the calibrated equation using the data collected in September led to a marked predictive bias to the data collected in December. All the above patterns were consistent for both species. Soil moisture, which exhibited strong seasonal variation in the study area, might be the key cause of variation in T_r. Our study is among the first to demonstrate seasonal variation in root mechanical traits, indicating that season potentially plays a non-negligible role in impacting soil reinforcement and slope stability by modifying roots’ mechanical quality.

Vegetation degradation in the alpine meadows is becoming increasingly severe under global change, with species loss frequently linked to changes in plant functional groups (PFGs). Changes in PFGs alter plant-derived carbon inputs, which significantly influence soil organic carbon (SOC) sequestration and soil communities. However, the impact of specific PFG removal on soil carbon fractions and nematode trophic groups remains underexplored. In this study, above-ground removal of PFGs was carried out for five consecutive years in the Qinghai–Tibet Plateau alpine meadow, with five treatments: (1) no removal of PFGs (CK); (2) keep non-legume forbs (remove graminoids and legumes, Forbs); (3) keep graminoids (remove legumes and non-legume forbs, Graminoids); (4) keep legumes (remove non-legume forbs and graminoids, Legumes); (5) remove all PFGs (All-plants-removed). Root properties, nematode community, and soil carbon fractions were measured. We found that the Graminoids treatment significantly increased root biomass, whereas the All-plants-removed treatment led to a significant decrease. Nematode abundance was highest under the Legumes treatment, primarily due to increased omnivores-predators. Meanwhile, the soil particulate organic carbon (POC) varied significantly between PFG types, being the highest in the Forbs and CK treatments. Correlation analysis revealed a significant positive relationship between SOC and bacterivore abundance, suggesting that higher SOC enhances bacterivore populations and subsequently influences carbon cycling. We conclude that PFG removal alters soil nematode community structure and POC, underscoring the role of PFGs in below-ground biodiversity and soil carbon sequestration.