Wind and sand control features are important tools for limiting desertification. Sand barriers are one of the oldest engineering measures used to reduce wind-sand hazards. Their efficacy and exact mechanism by which they work has remained a topic of scientific debate however. Sediment grainsize distributions can help constrain their utility and function. This research analyzed sediment grain size distributions in samples collected from areas around six different types of sand barriers installed along the southeastern margin of the Tengger Desert. Results were compared with sediment from a bare dune area (no barriers) used as a control. The barrier area samples contained high proportions of coarse sand and relatively low proportions of silty sand and very fine sand. Fine and medium sand were present but clay was not. The lower proportions of fine sand and higher proportions of coarse sand relative to bare dunes documented an effective reduction in aeolian transport by the barriers. Samples from the barrier areas also showed poorer sorting relative to bare dune areas. This appeared as lower kurtosis values and wider frequency distribution curves relative to those measured from bare dunes samples. The wider cumulative frequency curves for samples from the barrier areas likely reflects the higher proportion of coarse-grained material. The Straw/1.5 and PLA/1 barrier types hosted greater sediment accumulation than that observed for the other barrier types (Straw/1, PLA/1.5, Mixed/1 and Mixed/1.5). Sediment grain size distributions showed that the base and middle slope areas of the dune experienced deposition, while the top of the dunes experienced erosion. The Straw/1 barrier (straw installed as a 1 × 1 m grid) performed best in terms of installation costs and protective effects for the study area. This study demonstrates how sediment grain size distributions can be used as quantitative proxies for sand barrier performance in reducing desertification. Desertification is a major environmental problem that disrupts industrial activity, agriculture, transportation, mining and residential life. Economic and social impacts have led to various measures aimed at preventing desertification 1-4. Mechanical sand barriers typically used to combat desertification 5-7 can effectively control the movement of sand particles by increasing the surface aerodynamic roughness and by reducing wind speed near the surface. Mechanical sand barriers disrupt wind-sand flow and also reduce the ability of wind to carry sand leading to reduced erosion and transport and greater accumulation in different areas. Deposition of fine particles through this process leads to higher proportions of fine grained sediment within and around the sand barrier, which in turn supports soil development and vegetation 8. Grain-size distributions in surface sediments can therefore serve as a spatial proxy for aeolian processes. Underlying surface factors can also influence wind erosion 9,10 , which represents a first order driving mechanism in desertification. As th...
Wind erosion is an important part of environmental change research and represents a key destabilizing factor in arid and semi-arid ecosystems. The desert-oasis ecotone is an ecological barrier that protects oases from sandstorms. Nitraria tangutorum nebkhas help mitigate the impacts of wind erosion in desert-oasis ecotones. This study analyzed the relationship between vegetation coverage and soil grain size in a desert-oasis ecotone along the southeastern margin of the Tengger Desert. The results showed that the soil grain size distributions for nebkhas consisted primarily of fine, medium and very fine sand. The measured proportion of fine sand increased as vegetation coverage increased. The trailing edge of leeward slope and leading edge of windward slope positions contained higher proportions of coarse-grained material relative to other slope positions. Samples collected 0-5 cm depth contained higher proportions of fine-grained material than those collected at 5-10 cm depth. The average particle size ranges for nebkhas with low, medium, and high vegetation coverage were 1.644-2.430 φ, 1.601-2.911 φ, and 1.752-2.871 φ, respectively. Soil sorting degree was categorized as medium. Skewness values were extremely negative, negative, and positive respectively, and kurtosis levels were medium, narrow and medium, respectively. Samples collected from windward slope positions gave higher mean grain size values than those measured from samples collected along leeward slope and the top positions.
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