Abstract: Hemiptelea davidii forest is a peculiar forest type in Keerqin Sandy Land not recorded in references so far. Aimed to understand the biological and ecological mechanisms of the regeneration and expansion of H. davidii,a sampling line transect survey was conducted on the seed dispersal and seedling recruitment of H. davidii in its forest edges and forest understory, and an observation was made on the fruit shape and fruit-shedding characteristics of the plant. A majority of H. davidii seeds were found in the understory and around the edges, and the seed rain density decreased significantly beyond 3 m of the edges. Within the stands with high coverage, the regeneration of H. davidii population was mainly relied on root sucker recruitment. Because the distribution of H. davidii seedlings was not limited by terrain, the spatial expansion of the forest was mainly relied on the seedlings. Based on the observation on the fruit shape and fruit-shedding characteristics, it was considered that the biological features of H. davidii fruits could be the foundations of the local formation of H. davidii in Keerqin Sandy Land, whereas in other geographic distribution regions, H. davidii could only be a companion species.

Key words: Annual net primary productivity, Spatial distribution, Environmental conditions, Leaf area index, Canopy transpiration, Changbai Mountain Natural Reserve