Effects of Diaspore Traits and Vegetation Structures on Wind Dispersal of Solanum rostratum Using Wind Tunnel Simulations

The effects of diaspore traits and vegetation structure (VS) on the wind-dispersal processes of an invasive alien tumbleweed Solanum rostratum are not well understood. In this study, we used a wind tunnel to determine the wind velocity required for stem breakage of the plant. VSs of bare ground, desert steppe, typical steppe, and meadow steppe were simulated to determine the threshold wind velocity (TWV) of the plant (diaspore) and to measure diaspore velocity (DV) at wind velocities of 2, 4, 6, 8, 10, 12, and 14 m s⁻¹. The results showed that the stem of the plant did not break, even at a wind velocity of 14 m s⁻¹. The TWV is so high (> 6 m s⁻¹ on bare ground) that the diaspore could not move on the meadow steppe at a wind velocity of 14 m s⁻¹. Diaspore morphological traits and VS were key factors affecting the TWV, contributing 40.6% and 40.5%, respectively. Wind velocity, VS, and diaspore traits were the significant factors affecting DV, contributing 70.6%, 13.5%, and 6.6%, respectively. The DV significantly decreased from bare ground, desert steppe to typical steppe, and even remained still at a wind velocity of 14 m s⁻¹ on the meadow steppe. Therefore, the diaspore adopts an anti-long-distance wind-dispersal strategy when the plant stem does not break, or the diaspore adopts a non-long-distance wind-dispersal strategy once the plant stem breaks. Understanding the wind-dispersal mechanism of S. rostratum is of practical significance for predicting its distribution, controlling its spread range, and promoting the restoration of degraded vegetation.