Abstract: In order to reveal the space expansion potential of Hemiptelea davidiiwoodland in Keerqin sandy land in China, the quantitative spatial characteristics of the seed rain in the understory and at the woodsides, as well as the seed dispersal patterns at the woodsides and of the isolating trees, were analyzed through survey on sequential sampling away from seed source in different directions at the woodsides and isolating trees and random sampling in the understory. The results showed that among three sampling plots, the average density of the seed rain in the understory was the highest (13732.5±3106.2 seeds· m^-2). For isolating trees, the seed rain had the highest density (5449.4±1429.3 seeds·m^-2) in southeast transect, being significantly higher than that in other directions, and the lowest one (650.2±631.6 seeds·m^-2) in the northwest transect, being significantly lower than that in other directions. At the woodsides, the seed rain density was significantly higher in the east and south transects than in the west and north transects. The variation of the seed density was greater, with the variation coefficient being 25.7%-106.3% in different directions in the two plots of isolating trees and woodsides. Same as other anemochorous plants, H. davidiihad the characteristics of seed dispersal away from the seed source. In the eight sampling transects, there existed diversity in the patterns of the seed dispersal away from the seed source in per unit area and in accumulated area, including linear, power, exponential, quadratic parabola, and logarithmic functions. It was suggested that the space expansion potential of H. davidii woodland in Keerqin sandy land would be greater in more freq uency down wind directions such as the south, southeast, and east than in more frequency upwind directions such as the north, northwest, and west.

Key words: Hemiptelea davidii, seed density, woodside, understory, isolating wood, moths, Noctuidae, sex pheromone, biosynthesis pathway, PBAN, sex pheromone variation, species evolution.