Abstract:

Objective: In this paper, we explored the gender-differential responses of dioecious plants to interspecific competition using Rhamnus schneideri var. manshurica, with a view to providing a theoretical basis for the analysis of life history strategies under competitive stress. Method: A permanent fixed monitoring sample plot of 23.76 hm² was established in Jiaohe City, Jilin Province in July 2009. The diameter at breast height(DBH), tree height, first live branch height, and crown width of woody plants in the sample plots were measured, and their location coordinates were recorded, and retested in July 2014 and July 2019, respectively. A certain number of male and female plants were selected in the sample plots in 2019 flower and fruit period and 2020 fruit period. The new shoot, leaves, flowers and fruits of each Rhamnus schneideri var. manshurica plant were surveyed and sampled, and the biomass of each component was calculated for each plant. Quantifying the intensity of competition from neighboring heterospecific trees by means of the Hegyi index; differences in vegetative growth and reproduction in response to the intensity of interspecific competition between male and female individuals were compared using linear regression; differences in fruit number and fruit biomass of Rhamnus schneideri var. manshurica female trees in 2019 and 2020 were tested by means of ANOVA. Result: The Growth at DBH of female trees was significantly inhibited by interspecific competition (P<0.05), whereas the growth at DBH of male was not significantly correlated with the intensity of competition. Reproduction of both male and female plants was not significantly affected by competition, while new shoot and foliage biomass of female trees was significantly inhibited by interspecific competition during the flower period (P<0.05). Female trees had significantly higher fruit number and fruit biomass in the 2020 fruit period than in the 2019 fruit period (P<0.05), and their vegetative biomass was significantly suppressed by interspecific competition in 2020 (P<0.05), while it was not significantly affected by interspecific competition in 2019. Conclusion: There are no gender differences in the response of reproductive activity to interspecific competition in Rhamnus schneideri var. manshurica, and reproduction of both male and female plants was not affected by the intensity of competition. In contrast, the response of vegetative growth to interspecific competition showed significant gender differences, interspecific competition had more negative effects on the nutritional growth of female trees. The greater the input of female trees to reproduction, the greater their vegetative growth was negatively affected by interspecific competition. This suggests that an increase in reproductive inputs of female trees leads to an increase in the negative effects of interspecific competition on female trees.

Key words: dioecious, interspecific competition, gender differences, reproductive input, vegetative growth