| Since the 20th century,drought caused by climate change has seriously threatened the productivity and stability of global forest ecosystems.Artificial forest plays an important role in environmental protection and sustaining socio-economic development,but the poor stability and weak resistance of artificial forest ecosystem hinder the sustainable development and utilization of artificial forest.Populus species is an important tree species in artificial forest.As an important dioecious plant in angiosperms,it is important to exploit the differences in resource utilization and ecological niche differentiation between male and female poplar plants to construct a mixed male and female poplar forest,which is important to explore a highly productive and functionally stable plantation forest ecosystem.In this thesis,firstly,based on drought re-water experiments,we found that the soil bacterial community of P.cathayana,as a dioecious plant,has obvious sexual dimorphism and gender differences in response to drought stress.Then,based on this conclusion,competition experiments were used to explore moisture and competition-driven carbon transport capacity and growth dynamics of P.cathayana,starting from photosynthetic carbon allocation,rhizosphere soil bacteria,and root endophytes,setting up three competition modes and two moisture conditions.The sex differences in photosynthetic carbon sequestration,carbon transport and allocation of P.cathayana were explored by 13CO2 labeling,and the phospholipid fatty acid biomarker(13C-MBC)was used to investigate the sex differences in photosynthetic product(root exudates)utilization by soil microorganisms in the input soil,while the structure and composition of the rhizosphere soil bacterial community were then investigated to reveal the sex selection of soil microbial community by male and female P.cathayana.I found that different competition patterns between male and female P.cathayana can lead to significant differences in plant growth and development,resulting in different photosynthetic product distribution and different soil microbial utilization.Male plants of interspecific competition can promote the growth of female plants.The structure of rhizosphere soil bacterial communities differed significantly under different moisture conditions.The composition and structure of root endophytic bacterial communities were more sensitive to sex differences.Drought and intra-sexual competition exerted a greater negative impact on female than males in P.cathayana.Inter-sexual competition could alleviate the negative effects of drought on female P.cathayana root endophytes,increase the abundance of female P.cathayana rhizosphere resistance bacteria,ensure the number of female rhizosphere bacterial endemic species,and strengthen the stability of network structure and nutrient connectivity efficiency of female bacteria and endophytes.In conclusion,male and female co-cropping can effectively alleviate the mutual inhibition of intra-specific competition and improve female drought resistance.The intra-and inter-sexual competition experiments were used to explore the theoretical significance of constructing mixed male and female P.cathayana,which can provide theoretical basis and technical support for drought resistance research in artificial mixed forests. |
