Abstract: Although plant-plant interactions have been intensively studied, few studies examined sex-related neighbor interactions in dioecious plant species. Here, we investigated the sexual diffe-rences in biomass accumulation, and analyzed the sexual neighbor effects and yields of sexual combination in Populus cathayana seedlings under the treatments of inter- and intra-sex neighbors and soil sterilization. The results showed that biomass accumulation of P. cathayana decreased in both of sexes when grown with an intra-sex neighbor. Females increased biomass accumulation under non-sterilization condition when grown with an inter-sex neighbor. Soil sterilization decreased biomass accumulation in both sexes of these plants, especially for females. Soil sterilization treatments did not significantly affect intra-sex interactions, but neutralized the positive effects in females and led the effects in males to turn from neutral to negative in inter-sex neighbors. The highest biomass in female-male combination under non-sterilization condition and the lowest biomass in male-male combination under sterilization condition were observed among combinations. These results indicated that the growth of female and male P. cathayana differed in their responses to their sexual neighbors, and that such neighbor effects were affected by soil microorganism. Our results could contribute to improve the productivity of poplar plantations in silviculture.

Key words: plant neighbor effect, dioecy, soil microorganism, Populus cathayana