The spatial distribution of saturated hydraulic conductivity (Ks) is controlled by soil processes at multiple scales, and this spatial variability is crucial to simulating soil moisture movement. Nevertheless, few studies focus on the spatial variability of Ks and how changes through alpine meadow degradation or the specific scales at which the controlling factors function. This study therefore examines the scale-dependent relationships between Ks and several primary driving factors. Soil samples were collected at an interval of 3 m along three transects on a slope in the Qinghai-Tibet Plateau (QTP) and Ks, bulk density (BD), above-ground biomass (AGB), soil organic carbon content (SOC), sand content (SAND), silt content (SILT) and clay content (CLAY) were analysed. Ks showed strong spatial dependency and irregular distribution due to alpine meadow degradation. Pearson correlation analysis revealed a significant correlation between BD, AGB and Ks (p < 0.001). Furthermore, cross-semivariograms showed that Ks exhibited strong spatial correlation with AGB and SAND. Using the state space method, we determined that BD, SOC, AGB and CLAY are the main factors that control the spatial distribution of Ks on the slope. A two-factor state-space equation based on CLAY and BD provides a good representation of Ks, enabling the prediction and estimation of Ks distribution characteristics. These findings enhance our understanding of the crucial parameters that govern hydrological processes at the slope-scale of alpine grassland on the QTP, thereby helping to elucidate permafrost-related hydrological processes related to climate change.

Freeze-thaw desertification (FTD) as a specific land degeneration form in high elevations is intensifying in alpine meadows due to climate change and human activities. It causes the formation of desertified patches (DPs), and further aggravating alpine meadow patchiness and impairing ecosystem functions such as water conservation, carbon sequestration and biodiversity maintenance. However, the impacts of FTD on the patch pattern, soil properties, and vegetation succession of alpine meadows and the elevation differences of these impacts still lack a comprehensive understanding. Here, we analyzed the patch patterns, soil and vegetation characteristics in typical FTD regions in the Qilian Mountains using aerial photography and field investigations along an elevation gradient. Our results indicated that, as elevation increases, the fragmentation of alpine meadows caused by FTD intensified, which was related to the elevational differentiation of freeze-thaw cycles and soil water holding capacity. DPs not only led to a decrease in soil water holding capacity and an increase in bulk density, but also caused surface soil sandification. Among them, the weakening of soil water holding capacity by DPs was particularly serious in high elevations. Additionally, the degradation of the original vegetation species com-munities in DPs caused the significant loss of vegetation cover, biomass and soil organic carbon, and made DPs exhibit certain alpine desert steppe characteristics, whereas the vegetation diversity of DPs had an increase at low elevations. Our findings highlight the significant impacts of FTD on the water conservation function and vegetation diversity of alpine meadows, and it is necessary to apply ecological protection measures to control DPs expansion such as fenced grazing, biological control and land cover (crop, vegetation, degradable plastic mulch, etc.).