Regulation Mechanism Of Plant-soil Feedback On Plant Interspecific Relationships Under Elevated Temperature And Drought

Climate change will affect the growth and development of plants,as well as the composition of underground soil microbial community.Soil microorganisms play an important role in maintaining the stability and sustainability of grassland ecosystem,and the interaction between plants and between plants and soil microorganisms may change the composition of plant community.Under climate change conditions,plant interspecific relations will also be affected by soil microorganisms,Meanwhile,soil microorganisms play a crucial role in plant-soil feedback.However,little is known about how warming or drought can further affect plant properties and plant competition through the changes in soil microbial community composition and root traits in plant-soil feedback.The competition between the dominant species Leymus chinensis and subordinate species Kalimeris integrifolia in Songnen Grassland was studied under warming and drought.By verifying whether warming and drought would change plant-soil feedback,we can explore whether it would affect plant competition.The effects of warming and drought on plant-soil feedback of two plants growing under monoculture and competition conditions,the effects of warming and drought on soil microbial community and plant traits(plant biomass and root functional traits)were studied,which reveals the competition mechanism between the two plants.The results are of great significance for clarifying the changes in dominant species and community composition in Songnen grassland under climate changes.The main results are as follows:(1)The elevated temperature and drought significantly altered soil bacterial community composition but had no significant impact on the soil fungal community.A significant difference in soil bacterial and fungal community compositions was observed between the soil conditioned by K.integrifolia and L.chinensis.The relative abundance of Proteobacteria and Mortierellomycota in K.integrifolia conditioning soil significantly reduced,while the relative abundance of Chloroflexi and Gemmatimonadetes increased.Proteobacteria and Acidobacteria bacteria are the dominant species of all bacterial communities according to all treatments,and Ascomycota is the dominant fungal species.The results of redundancy analysis(RDA)showed that soil water content was the main factor for driving the change of soil fungal community composition,and soil p H,conductivity,soil water content and soil total nitrogen content were the main influencing factors for the change of soil bacterial community composition.(2)The effects of elevated temperature and drought on the aboveground and belowground biomass of the two plants were different,which is also related to the soilconditioned by different plants.Under elevated temperature,the aboveground biomass of K.integrifolia in the soil conditioned by K.integrifolia was significantly higher than that in the soil conditioned by L.chinensis.The elevated temperature improved the growth of L.chinensis in the soil that has been domesticated by itself,while the plant-soil feedback of K.integrifolia was negative.At the same time,elevated temperature also indirectly affects the plant competition interaction by influencing the plant-soil feedback,but it is related to the type of conditioned soil.In the L.chinensis conditioned soil,elevated temperature significantly improved the competitiveness of L.chinensis,but in the K.integrifolia conditioned soil,but weakened the competitiveness of L.chinensis in its soil and enhanced the competitiveness of K.integrifolia.(3)Plants can adapt to elevated temperature and drought by constructing different root traits to improve their competitiveness.Under drought condition,L.chinensis could quickly obtain resources and improve its conservation capacity by increasing the root: shoot ratio,root length,specific root length and specific root area in competition;under elevated temperature,the nutrient supply efficiency of the root system can be improved by increasing the root diameter,root tissue density and reducing the specific root area.The change of root functional traits might have an impact on the final interspecific competition between different species.In summary,elevated temperature and drought have significant effects on soil microorganisms in the plant-soil feedback,mainly to alter the composition and species diversity of soil microbial communities,so that plants can respond quickly toward adaptive growth conditions.The response of soil bacterial and fungal community composition to elevated temperature and drought is inconsistent.Soil bacteria are more sensitive than soil fungi,and have a greater impact on plant growth in the feedback stage.Meanwhile,the elevated temperature and drought affected the plant root traits in the feedback stage,and elevated temperature also made K.integrifolia grow better in its own conditioned soil,and then the root traits of the feedback stage plant were also changed by enriching more beneficial microorganisms in the first stage,and the plant root diameter was higher,which further enhanced the competitiveness of the K.integrifolia.The research results are helpful to better predict the response of plant community composition of Songnen grassland to global change.