Abstract: An investigation was made on the population sex ratio and spatial distribution of dioecious tree species Pistacia chinensis within a 100 m × 140 m plot. In the plot, there were 2116 P. chinensis individuals with diameter at breast height (dbh) ≥4 cm, among which, 526 were females, 1200 were males, and 390 were undetermined. The sex ratio (males/females) was 2.28, indicating a significant male-biased sex ratio (P<0.001). The average dbh of the females and males was 7.34 cm and 7.81 cm, respectively, and the difference was significant (P<0.05). The saplings, females, and males all showed a significant clumped distribution. The saplings showed significant attraction to the females and males at small scales, while the females showed significant repulsion against the males at 0-50 m scales, i.e., the females and males exhibited spatial segregation. A significant repulsion also exhibited between different size and different sex individuals.

Key words: Veterinary medicines, Ecotoxicology, Environmental impact