Lateral migration differs between phytolith morphotypes on sand dune surfaces

Abstract

Arid and semi-arid lands are exceptionally sensitive to climate change. However, the application of phytolith analysis to these environments is hindered by the potential for lateral migration of phytoliths during wind erosion, which may affect the reliability of phytolith-based paleoenvironmental reconstructions. Moreover, there is a lack of quantitative studies of the dispersion and deposition of phytoliths by wind erosion. Here we apply Sutton's equation and theoretical models from the field of blown sand physics and engineering to quantify the lateral migration of various phytolith morphotypes in the surface soil of sand dunes in the Horqin Sandy Land in China. Phytolith morphotypes and concentrations were determined in addition to sedimentary organic matter content and grain size. Combined with the analysis of plant communities, these measurements were used to quantify the lateral migration of phytolith morphotypes, and the results were compared with theoretical models. We found that phytolith concentrations decreased exponentially under an annual average wind speed with distance from the surface source; specifically, a large proportion of lateral phytolith migration occurred within the distance of ~3–5 m. There were significant linear correlations between the phytolith concentration and other environmental factors. A comprehensive form of Sutton's equation was used to estimate that a relatively large proportion (8.35%) of short-cell phytoliths may migrate laterally on dunes that are vulnerable to wind erosion. However, large phytoliths are deposited almost in situ, and relatively limited lateral migration of wind-transported phytoliths occurs in the Horqin Sandy Land overall. Our results provide a theoretical model and practice template for the application of phytolith analysis to soil and sediments, especially as a proxy of past vegetation and ecological change in the Horqin Sandy Land, and other areas affected by wind erosion. Additionally, short-cell phytoliths in palaeoenvironmental contexts satisfy the criteria necessary to investigate the extent with frequent aeolian activity.