黄土丘陵区切沟侵蚀发育过程中土壤侵蚀阻力变化OA

[Objective]Gully morphological characteristics are key parameters for quantifying gully erosion development,and its evolution is governed by the dynamic balance between hydraulic shear stress and soil erosion resistance.However,a systematic quantitative understanding is lacking regarding how soil erosion resistance evolves at different gully positions with developmental stages and feeds back to morphological evolution during gully erosion development.[Methods]This study investigated typical gullies on slopes in the loess hilly region.Field surveys and laboratory analyses were conducted to systematically compare soil erosion resistance characteristics across different developmental stages(early,middle,late),gully morphologies(wide,narrow),and positions(head,wall,floor).[Results]As gully development progressed,critical shear stress(τc)of soil significantly increased from(2.19±1.39)Pa in the early stage to(3.11±1.92)Pa in the middle stage and to(3.62±2.77)Pa in the late stage.Rill erodibility(kd)significantly declined from(320.46±424.21)cm3/(N·s)in the early stage to(121.28±145.99)cm3/(N·s)in the middle stage and to(51.20±36.93)cm3/(N·s)in the late stage,indicating that soil erosion resistance was significantly enhanced in the later stage of development.Random forest model revealed this enhancement was primarily related to changes in soil and root properties,with soil organic matter content being a key factor influencing both τc and kd.The increase in τc was closely associated with root weight density,while the decrease in kd was mainly attributed to increasing aggregate stability.These patterns suggested that soil structure reconstruction and root development during gully development jointly contributed to the overall increase in soil erosion resistance.This evolution trend exhibited significant spatial differentiation,with pronounced differences in soil erosion resistance across different geomorphological positions.Gully head showed the highest τc[(4.59±2.21)Pa]and lowest kd[(44.81±25.79)cm3/(N·s)],gully wall had the lowest τc[(1.34±0.61)Pa]and highest kd[(380.06±406.89)cm3/(N·s)],and gully floor displayed intermediate values.These values indicated that wall collapse and floor incision were the primary active erosion modes.Gully morphology further regulated the spatiotemporal pattern of erosion resistance.Compared to wide gullies,narrow gullies exhibited higher kd and lower τc,suggesting greater sensitivity to erosion.Linear mixed-effects modelling quantified the sources of variation in soil erosion resistance from the perspective of macro-geomorphological factors such as developmental stage,geomorphological position,and gully morphology.The results showed that these three factors jointly explained 52.2％of kd and 58.2％of τcvariation,with a significantly pronounced interaction between developmental stage and geomorphological position(p＜0.001).These findings demonstrated that soil erosion resistance exhibited differentiated responses at different positions as gully development progressed and was conditioned by gully morphology.Overall,the developmental stage determined the overall trend of soil and root property evolution,whereas geomorphological position and gully morphology modulated this evolution by shaping local hydrodynamics and provenance conditions,thereby jointly controlling the spatiotemporal pattern of soil erosion resistance.[Conclusion]This study reveals the quantitative law of the coupling between gully development and soil erosion resistance,providing a scientific basis for gully erosion control and ecological restoration in the loess hilly region.