Study On The Role Of Soil Microbes In The Effect Of Plant Diversity On Community Invasibility

The impact of biological invasion on habitat destruction is becoming increasingly serious,and it has caused significant losses,which has become one of the increasingly serious global problems.In addition to understanding the invasiveness of invasive plants,the invasibility of native plant communities is also an important factor affecting the degree of invasion.Previous studies showed that there is a positive or negative correlation between plant diversity and invasibility,however,the role and mechanism of soil microorganisms in the regulation of community invasibility by plant diversity are not clear.It is of great significance to strengthen the study of the impact of native plant diversity on community invasibility,improving the understanding of biological invasion mechanism,controlling invasive plants and conserving plant diversity.In this study,the non-mycorrhizal plant Phytolacca americana and the arbuscular mycorrhizal plant Rhus typhina,which cause serious harm to the Shandong Peninsula,were used as the test plants.The plant diversity communities composed of nine common plants in Kunyu Mountain,such as Indigofera kirilowii,Grewia biloba var.parviflora,Lespedeza bicolor,Rhus chinensis,Pinus densiflora,Ailanthus altissima,Quercus acutissima and Q.variabilis,were used as test objects to explore the response of invasive plants of two mycorrhizal types to plant diversity soil mixture and its influencing factors.Analyzing whether this effect is affected by environmental conditions such as soil nutrients and plant competition patterns,try to reveal the impact of plant diversity on community invasibility and its mechanism,and provide data support for further understanding of community invasibility.In this study,three parts of experiments are designed,and the main results are given below.(1)Potting and soil inoculation experiment were used to explore the effects of soil with different plant species diversity combinations on the growth of invasive plants and the role of soil microorganisms in this process.The results showed that the effects of diversity levels on the biomass accumulation of P.americana and R.typhina in the live soil were insignificant,but their biomass allocation was affected differently.The two invasive plants also had different responses to soil treatments and its fungi.Both sterilized and inoculated experiments showed that the growth of P.americana was inhibited by soil micoorganisms,while that R.typhina of was promoted.There was a significant positive correlation between R.typhina and soil fungi Fusarium and Mortierella.It was emphasized that diversity resistance hypothesis was not fully reflected in warm temperate forest ecosystems,and the effects of soil microbial composition influenced by plant diversity level on the growth performance of invasive plants were related to the mycorrhizal types of invasive plants.(2)A pot experiment was conducted to explore the effect of environmental conditions on the “diversity-invasibility” relationship of soil microorganisms.The results showed that plant diversity had insignificant effect on the size traits of P.americana and R.typhina.There was an interaction between plant diversity and nitrogen addition on the plant height of two invaders.The plant height of P.americana and R.typhina decreased with the increase of plant diversity level(P.americana at N8,R.typhina at N8 and N20).Plant competition could only change the response of P.americana to plant diversity,and the total biomass accumulation of P.americana was the lowest under hight community(mixed soil of 6 native plant species).In addition,the plant-soil feedback strength of the two invasive plants on species-richness was different under different environmental conditions.Morever,the negative feedback of interspecific competition on P.americana plants was most obvious under N8 and increased with the plant diversity level.However,the positive feedback of interspecific competition on R.typhina was greater than that of interspecific competition at N0,and the positive feedback of intraspecific competition was greater than that of intraspecific competition at N20.These results suggest that the role of soil microorganisms in the“diversity-invasibility” relationship is affected by certain environmental conditions.When we extrapolate the effects of environmental conditions on soil microbes in the“diversity-invasibility” relationship to natural habitats,we also need to consider the species characteristics of invasive plants,such as plant life forms,phynotypic plasticity,nitrogen utilization strategies,mycorrhizal types,and so on.In summary,the main findings of this study will promote our understanding the role of soil microorganisms in plant diversity affecting community invasibility,the impact of environmental conditions on this role or possible response mechanisms.It provides new thinking for the follow-up study of the relationship between diversity and invasibility,and provides data support and theoretical guide for the prevention and control of invasive plants under the global change.