Rhizosphere bacterial communities and soil nutrient conditions reveal sexual dimorphism of Populus deltoides

Sexual dimorphism of plants shapes the different morphology and physiology between males and females. However, it is still unclear whether it influences belowground ecological processes. In this study, rhizosphere soil of male and female Populus deltoides and bulk soil were collected from an 18-year plantation (male and female trees mix-planted) and grouped into three soil compartments. Soil carbon (C), nitrogen (N) and phosphorus (P) levels were determined, and soil bacterial communities were analyzed by high-throughput sequencing. The results showed the less total carbon and total organic carbon, the more nutrients (available phosphorus, nitrate nitrogen and ammonium nitrogen) available in the rhizosphere soils of female poplars than soils of males. However, α-diversity indices of the rhizosphere bacterial communities under male plants were significantly higher. Principal component analysis showed that the bacterial communities were significantly different between the male and female soil compartments. Further, the bacterial co-occurrence network in soil under male trees had more nodes and edges than under females. BugBase analysis showed the more functional bacteria taxa related to biofilm formation and antioxidation under males. The results indicate that soils under male poplars had more diverse and more complex co-occurrence networks of the rhizosphere bacterial community than soils under female trees, implying that male poplars might have better environmental adaptability. The study provides insight into the different soil-microbe interactions of dioecious plants. More details about the influencing mechanism of sexual dimorphism on rhizosphere soil bacterial communities need to be further studied.