Gully erosion is well-developed in the Jinsha dry-hot valley region, which has caused serious soil losses. Gully volume is regarded as an effective indicator that can reflect the development intensity of gully erosion, and the evolutionary processes of gullies can be predicted based on the dynamic variation in gully volume. Establishing an effective prediction model of gully volume is essential to determine gully volume accurately and conveniently. Therefore, in this work, an empirical prediction model of gully volume was constructed and verified based on detailed morphological features acquired by elaborate field investigations and measurements in 134 gullies. The results showed the mean value of gully length, width, depth, cross-section area, volume, and vertical gradient decreased with the weakness of the activity degree of the gully, although the decrease in processes of these parameters had some differences. Moreover, a series of empirical prediction models of gully volume was constructed, and gully length was demonstrated to be a better predictor than other morphological features. Lastly, the effectiveness test showed the model of V = aL^b was the most effective in predicting gully volume among the different models established in this study. Our results provide a useful approach to predict gully volume in dry-hot valley regions.

Changes in land use can alter the physicochemical properties of soil, thereby leading to variations in soil erosion resistance. In the past few decades, land use has changed very rapidly in the arid valley region in the Anning River Basin of Southwest China, but the impact of these changes on soil erosion resistance is still not yet clear. Thus, five typical land use types in this region, namely woodland, cropland, orchard land, abandoned land, and grassland, have been selected to explore the impact of land use types on soil erosion resistance, including factors such as the mean weight diameter (MWD), dispersion rate (DR), clay ratio (CR), soil organic carbon cementing agent index (SCAI), soil structure stability index (SSSI), K-factor, and comprehensive soil erosion resistance (CSER). The results showed that the land use type had a significant effect on soil erosion resistance, but the intensity of its influence varied across each soil erosion resistance index. Generally, woodland, abandoned land, and grassland demonstrated higher erosion resistance compared to cropland and orchard land. Additionally, surface soil exhibited stronger erosion resistance compared to subsoil, with the impact of land use types primarily concentrated in the surface soil layers. Moreover, soil organic matter content (SOM) emerged as the primary factor influencing soil erosion resistance. The research results can provide valuable guidance for regional land-use planning, aiming to reduce soil erosion and enhance the ecosystem’s service capacity, and can provide a theoretical basis for trade-offs between ecosystem services and food security.

Gully erosion is a common form of soil erosion in dry-hot valleys, and it often brings serious land degradation. A multi-criteria method integrating the characteristics of the longitudinal profile (LP), the cross profile (CP) and the knickpoints of gullies was applied to identify the development stage of gullies in Yuanmou County, Yunnan Province, in southwestern China. Firstly, based on the high-resolution data sources produced by an unmanned aerial vehicle (UAV), 50 gullies were selected as the typical ones in Tutujiliangzi and Shadi village. The LPs were extracted, and their morphological indices, information entropy and fitting functions were calculated. The morphological characteristics of the CPs and the presence or absence of knickpoints were recorded. The results show that the period of the gullies in Tutujiliangzi and Shadi is dominated by the deep incision period and the equilibrium adjustment period, which means that most gullies are in the period of the severe erosion stage. Among the gullies, 13 LPs’ morphological index is between 0.636 and 0.933, and the morphology of the LP presents an upward convex shape; the cross profiles are mainly V-shaped and U-shaped. Thirty-two LPs’ morphological index is between 1.005~2.384, which presents a slightly concave shape; the cross profiles are mainly repeated U-shapes. The remaining five LPs have a morphological index of 0.592, 0.462, 1.061, 1.344 and 0.888, respectively; the LPs of upstream and downstream are different. The LPs of the Tutujiliangzi gullies are nearly straight lines and slightly concave, while those of the Shadi village gullies are convex and nearly straight lines. The knickpoints and step-pools in Shadi village are more developed, while the gullies in Tutujiliangzi develop more rapidly. This study shows that in counties with similar conditions, these conditions such as temperature and precipitation, local topographic changes, soil properties and vegetation conditions have obvious effects on the development of gullies.

Runoff and sediment transport rates are important indicators for guiding regional economic development and ecological protection. It is important to clarify the dynamic evolution processes and inner connection of runoff and sediment transport rate for the rational development of soil and water resources in Longchuan River. In this study, the Mann-Kendall test, wavelet analysis and synchronization analysis have been used to analysis the change trend, mutation situation and variation cycles of runoff and sediment transport rate. The results showed that: runoff volume was generally stable, and sediment transport rate experienced a significant increasing trend at a rate of 4.29 kg/s/a in 1970-2008 in Longchuan River. The change cycles of runoff volume and sediment transport rate were different. The first principal cycles of seasonal and annual runoff volume were all 25a, while the second and third principal cycles were different. In contrast, the first and second principal cycles of sediment transport rate were respectively 29a and 6a. There was a significant linear relationship between sediment transport rate and runoff although the relationship between water and sediment was only synchronous in 1991-2008.