Growth Characteristics And Soil Traits Of Amphibious Vetiveria Zizanioides And Pennisetum Alopecuroides Under Water Stress

The composition of plant communities depends on the physical,chemical and biological characteristics of the soil.At the same time,plants can affect nutrient cycling and soil properties by absorbing nutrient elements,controlling physiological mechanisms and of root exudates.The responses to water-level fluctuation most vividly reflected in the morphological characteristics of the plant,but also in the underground.The ecological strategies and measure controlled by resource allocation and compensation mechanism of plants,finally achieved through the fine coordinating internal and external traits.Plant interspecific interaction is also one of the main driving forces to shape plant morphology,life history and population domestication.At the same time,it also determines the structure,function and dynamic characteristics of the ecosystem.In this study,a bucket water control simulation experiment was conducted according to the specificity of natural and artificial wetland by setting up three types of water stress as "continuous flooding","continuous drought" and "flooding-drought alternation”,as well as single and mixed these two planting modes.The response of amphibious Vetiveria zizanioides and Pennisetum alopecuroides with different planting modes to soil water stress were analyzed from “soil traits”,“growth traits” and “interspecific interactions”.Research indicates:(1)In the normal irrigation,V.zizanioides and P.alopecuroides can reduce the pH value of soils in each soil layers under different planting mode,which decreased significantly(P<0.05)in 0~10 cm soil layer when V.zizanioides planted single and the two plants mixed.Under all plant modes,the soil organic carbon(SOC)and total nitrogen(TN)content decreased significantly(P<0.05)in each soil layer and soil nitrogen ratio(S-C/N)increased.(2)The pH value of soils decreased when V.zizanioides planted single through continuous flooding,P.alopecuroides planted single and the two plants mixed through continuous drought.S-C/N increased when V.zizanioides planted single through all kinds of water treatment,P.alopecuroides planted single through continuous drought and the two plants mixed through continuous flooding and flooding-drought alternation respectively.(3)The adaptation of the two plants to different water environment mainly based on the change of root morphology(root length,root surface area,root volume,etc.)and underground biomass allocation and supplemented by the tillers and plant height.(4)The interaction between two plants is different when planted mixed with different water treatments.They showed a symbiotic relationship through flooding-drought alternation and competitive relationship through both continuous flooding and drought.V.zizanioides showed stronger competition ability with continuous flooding and its interspecific competition is greater than the intraspecific competition,well the competition of P.alopecuroides is on the contrary.P.alopecuroides showed stronger competition ability with continuous drought and the interspecific competition is greater than the intraspecific competition in each plant.(5)The two plants adapt to water stress actively without interspecific competition.The aboveground is characterized as biomass,tiller number increased and plant height decreased,and the underground is characterized by increasing biomass and root length,root surface area,root volume and various root indexes calculated.With interspecific competition,the poor tolerance one to soil water stress will take evasive strategies in terms of morphology,and its characteristics of the aboveground and underground growth are opposite to the above changes.(6)In general,V.zizanioides has strong flood resistance and P.alopecuroides has strong drought resistance.Both of them can tolerate a certain degree of flooding-drought alternation stress,but V.zizanioides is more tolerant.It is suggested that V.zizanioides should be planted alone in water saturated or long-term flooded environment,P.alopecuroides should be planted alone when continuous drought or rapidly drying after flooding and the two species should be mix planted when flooding and drought exists alternately.