Background Severe soil erosion in the Dry-Hot Valley of the Jinsha River causes significant challenges to the zone’s ecological security and functions, seriously affecting social and economic activities. Investigating the soil and water conservation characteristics and influencing factors of natural forests, planted forests, and savanna of valley type in the upper, middle, and lower reaches of the Dry-Hot Valley of the Jinsha River is crucial for soil and water conservation and ecological restoration in this zone.

Methods In this study, 22 sampling sites were established in the upper reaches, 13 sampling sites in the middle reaches, and 12 sampling sites in the lower reaches. Data were collected through comprehensive field investigations, sample collection, and subsequent laboratory analysis, and the soil and water conservation capacity characteristics and influencing factors of natural forests, planted forests, and savanna of valley type in the upper, middle, and lower reaches were studied.

Results 1) Natural forests show the best characteristics in terms of surface vegetation, soil porosity, and soil water-holding capacity, resulting in the strongest soil and water conservation ability. In contrast, savanna of valley type are of poor surface vegetation growth, a thin litter layer, low soil porosity, and weak soil water-holding capacity, making them more susceptible to severe soil erosion from rain. Therefore, the soil and water conservation capacity under different vegetation types is natural forests > planted forests > savanna of valley type. 2) Soil density gradually increases from upstream to downstream, while soil porosity, soil water-holding capacity and soil drainage capacity gradually decrease from upstream to downstream. Therefore, the soil and water conservation capacity in the upper, middle, and lower reaches of the Dry-Hot Valley of the Jinsha River is as follows: upper reaches > middle reaches > lower reaches, the difference in soil water conservation capacity between the middle and lower reaches is not significant (P > 0.05). 3) The characteristics of soil porosity and soil water-holding capacity of the surface layer (0−15 cm) are superior to the subsurface layer (15−30 cm) in different sections of the Dry-Hot Valley of the Jinsha River. Therefore, the soil and water conservation capacity of surface and subsurface layers soils in the Dry-Hot Valley of the Jinsha River is as follows: surface layer > subsurface layer.

Conclusions The soil under planted forests shows substantial improvement compared to savanna of valley type in terms of vegetation growth state, coverage, soil porosity, and soil water-holding capacity. This indicates that artificial afforestation measures effectively promote soil and water conservation and ecological restoration in the Dry-Hot Valley of the Jinsha River, indicating that it is an effective measure for preventing and controlling soil and water loss.