The impact of a multiple-row Tamarix windbreak on grain size parameters of aeolian sand flux

Authors: MIRI, AUBBAS - Agricultural University Of Tirana, Albania; Webb, Nicholas - Nick

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2023
Publication Date: 2/13/2024
Citation: Miri, A., Webb, N.P. 2024. The impact of a multiple-row Tamarix windbreak on grain size parameters of aeolian sand flux. Soil Science Society of America Journal. 88(2):482-497. https://doi.org/10.1002/saj2.20623.
DOI: https://doi.org/10.1002/saj2.20623

Interpretive Summary: Windbreaks and shelterbelts are used around the world to protect soils from strong winds that can cause erosion. Understanding how windbreaks reduce soil movement by wind and influence the size of eroded material is important for designing windbreaks to optimize their benefits. This field study sought to determine gain-size parameters (mean, standard deviation, skew and kurtosis) of eroded sediments upwind, within and downwind of a multi-row Tamarix windbreak. Over three dust storm events, sediments were collected at seven heights (z/h = 0.05, 0.1, 0.2, 0.4, 0.8, 1.4 and 1.8 where h is the mean height of the windbreak) at locations upwind (x =100 m), within (x = 100 and 256 m) and downwind (x = 448 and 560 m) of the windbreak. The vertical distribution of grain size parameters indicated that mean grain size may decrease with height upwind of the windbreak and inflections were observed in the profiles of sorting, skewness and kurtosis within the windbreak, which may be attributable to vegetation effects. Sediment showed poorly sorted sands, very fine skewed and a leptokurtic kurtosis. Horizontal distribution of grain size parameters indicated that mean grain size, skewness and kurtosis may increase, and sorting decrease from upwind (x = - 100 m) to within (x = 100 m) of the windbreak. Downwind of the windbreak (at x = 448 and 550 m) mean grain size and kurtosis may increase, and sorting and skewness decrease. Results of the current study provide preliminary information on the variability of wind-eroded sediment grain sizes during transport and suggest that multirow windbreaks could influence downwind air quality and soil health.

Technical Abstract: Understanding the effects of windbreaks on aeolian sediment transport rates, and the size distribution of aeolian sediments transported through them, is important for designing windbreaks to optimize their wind erosion mitigation benefits. This field study determines the size distribution of aeolian sediments upwind (x = -100 m), within (x = 100 and 256 m) and downwind (x = 448 and 560 m) (where x is the distance from the first row of windbreak) of a multi-row Tamarix windbreak as the basis for further investigation of the influence of vegetation on aeolian sediment characteristics. The volumetric percentage of grains around the peaks of 100 and 20–30 µm showed variability with distance and between the three measured events. We found that the vertical distribution of grain size parameters indicated that mean grain size (Mz) may decrease with height upwind of the windbreak, and inflections were observed in the profiles of sorting (s1), skewness (SK), and kurtosis (KG) within the windbreak, which may be attributable to blocking and trapping effect of the vegetation. Sediments were poorly sorted with the distributions of grain sizes being fine-skewed and leptokurtic. The horizontal distribution of grain size indicated that Mz increased from x = -100 m to x = 100 m and then decreased at x = 256 m, indicating that the windbreak was unable to retain small particles. The windbreak could trap particle sizes <50 µm and particles >50 µm transported to downwind region of windbreak. Within the windbreak, SK and KG increased, and s1 decreased. Downwind of the windbreak (at x = 448 and 560 m), Mz and KG increased, and s1 and SK decreased. The results of the current study provide preliminary information on the variability of aeolian sediment grain sizes during transport relative to vegetation and suggest that multirow windbreaks could influence downwind particulate matter size concentrations and soil health.