Lift-off velocity of diaspores during secondary wind dispersal varies with particle size of the underlying surface matrix

Purpose: All secondary dispersal by wind, important for predicting, modeling and regulating diaspore dispersal processes, and for biodiversity conservation and vegetation restoration, is influenced by underlying surface matrix. But little is known about how matrix determines diaspore secondary dispersal. Here we focus on how lift-off velocity, good proxy for secondary dispersal of seeds by wind, is linked to the underlying surface matrix. Methods: We investigated the effect of the underlying surface matrix on diaspore lift-off velocity in a wind tunnel. Our study used 11 matrix types with different particle size, including four pure substrates (loam, aeolian sand, river sand, gravel) and seven mixtures thereof and diaspores of 28 species differing in length, width, height, mass, projected area, shape index, wing loading, and terminal velocity. Results: Diaspores were more easily dispersed from loam, aeolian sand and river sand than from the gravel substrates. For mixed matrices, lift-off velocity was closer to that of the small-sized than of the large-sized component of the substrate. Underlying surface matrix contributed more to diaspore dispersal by wind than diaspore attributes. In addition to wing loading, terminal velocity, and projected area also were important diaspore attributes determining lift-off velocity of the diaspores. Conclusion: Lift-off velocity of diaspores is influenced by particle size of underlying surface matrix during secondary wind dispersal: lift-off velocity is the largest on large-sized particles for pure matrices, and determined by the small-sized component for mixed matrices.