雅鲁藏布江中下游河谷地带不同风蚀类型下垫面土壤分形特征及沙尘释放潜力研究OA

To quantitatively evaluate the dust emission potential in plateau valley regions and reveal the coupling relationship between wind erosion sensitivity and soil particle size characteristics under the regulation of"Venturi effect",soil particle size distribution(PSD)analysis was conducted on soils from six types of wind erosion underlying surfaces(woodland,grassland,cultivated land,floodplain,fixed sandy land,and shifting sandy land).A wind-sand dynamic model was constructed to quantify differences in potential dust emission flux,elucidate the spatial differentiation characteristics of dust sedimentary landforms in the middle and lower reaches of the Yarlung Zangbo River valley.The results showed that:1)The wind-eroded soils in the study area were predominantly sandy loam,loamy sand,and sand.Fine sand constituted the highest proportion in surface wind-eroded soils(26.62％-46.93％),while clay content was extremely low(0％-1.39％).The fine sand proportion in near-surface soils of floodplain and shifting sandy land was significantly lower than that of other underlying surfaces(P＜0.01).Soil monofractal dimension exhibited extremely significant positive correlations with both clay and silt content(P＜0.01).2)The generalized dimension spectrum curves for the six underlying surfaces all showed a reverse S-shaped monotonic decreasing trend.Both monofractal and multifractal dimension analyses consistently indicated that woodland had the highest soil particle size distribution heterogeneity,while floodplain and shifting sandy land had the lowest.The capacity dimension(D0)of cultivated land reflected the widest range of particle size composition,and the information dimension(D1)of woodland indicated the highest soil heterogeneity.3)Sediment transport flux(Qh)calculated by the Bagnold wind-sand dynamic model increased exponentially within the wind speed range of 8-14.0 m/s.Among them,shifting sandy land(threshold wind velocity Ut=6.55 m/s;Qh=0.738-91.970 kg/(m·s))and floodplain(Ut=7.02 m/s;Qh=0.132-66.010 kg/(m·s))exhibited strong wind erosion sensitivity;cultivated land(Ut=7.23 m/s;Qh=0.085 7-52.140 kg/(m·s))and semi-shifting sandy land(Ut=6.90 m/s;Qh=0.227-61.060 kg/(m·s))showed transitional characteristics of moderate wind erosion sensitivity.In summary,the optimized wind-sand dynamic model based on soil particle size composition and environmental factors across different wind-eroded surfaces can reveal the coupled response mechanism between the threshold wind velocity for sand emission and sand transport flux,thereby providing data support for the evaluation and prediction of dust emission potential in plateau valley regions.