Diaspore burial during wind dispersal depends on particle size of the underlying substrate

Purpose: Burial of diaspores has significant influence on diaspore fate, seedling recruitment and population dynamics. Some studies indicated that wind speed determines burial, neglecting the effect of matrix. Burial during wind dispersal basically occurs at the matrix surface. However, little is known about how substrate, wind speed and diaspore attributes interact to determine burial. Methods: Four pure substrates with a wide span of particle sizes (from 89.10 μm to 25000 μm) were selected to investigate how the particle size affects burial. Since the real substrates in nature are mainly mixtures of these substrates in different proportions, seven mixtures were also designed to represent some real filed matrices (farmland, riparian, desert and Gobi). Diaspores from 28 species with various length, width, height, mass, shape index, projected area, terminal velocity and wing loading were selected for the burial experiments simulating by a wind tunnel. Results: Substrate but not diaspore attributes or wind speed, contributed the most to burial during wind dispersal. Burial was poorest when placed on a matrix of intermediate-sized particles (200-600 μm) at a high wind speed. With increased matrix particle size, increased wind speed changed from promoting to inhibiting burial. Effects of diaspore attributes on burial were only significant on a substrate with large particle size at all wind speeds or a substrate with small particle size at high wind speeds. Conclusion: Our most important finding is that diaspores are most difficult to be buried by wind if they are dispersal onto a substrate with intermediate-sized particles.