Interference Of Allelopathy Of Phragmites Australis On Ecological Stoichiometric Balance,Growth And Nutrient Strategies Of Phalaris Arundinacea L.

In this study,we used Phragmites australis in Zhenjiang Riverside Wetland as the allelopathic donor plant and Phalaris arundinacea as the allelopathic receptor plant,under different allelopathic intensities of Phragmites australis,to explore the changes of ecological stoichiometry characteristics of Phalaris arundinacea throughout the growing season(pre-slow growth stage,fast-growth stage and post-slow growth stage),and discussed whether the allelopathy(by limiting nutrient absorption)could inhibit the growth of Phalaris arundinacea by interfering its ecological stoichiometric balance.This study lays a theoretical foundation for further study of allelopathy inhibition mechanism.The results are as follows:(1)Under the absence of allelopathy,both Phalaris arundinacea and Phragmites australis had different ecological stoichiometric balance characteristics in their growth stages,respectively.(2)In each growth stage of Phalaris arundinacea,with the increasing density of Phragmites australis(0 plants·m^-2,10-14 plants·m^-2,24-28 plants·m^-2,40-44plants·m^-2),the content of total phenolic acids in the soil layer(0-30 cm)increased significantly(P<0.05),while the aboveground biomass of Phalaris arundinacea decreased significantly(P<0.05).The above three were strongly correlated.Meanwhile,the coefficient of balance deviation of the aboveground biomass of Phalaris arundinacea increased significantly with the increase of the reed density.The aboved results indicated that the intensity of allelopathy increased with the increase of the Phragmites australis density,and the degree of inhibition of Phalaris arundinacea increased.(3)In each growth stage of Phalaris arundinacea,with the increase of allelopathic intensity and growth inhibition,N,C:P and N:P increased,while P and C:N decreased.Moreover,the coefficient of balance deviation of all indicators increased.Among them,the coefficient of balance deviation of N:P was the largest.The aboved results indicated that allelopathy of Phragmites australis interfered with nutrient absorption of Phalaris arundinacea,and deviated its ecological stoichiometry from equilibrium.Finally,Phragmites australis inhibited the normal growth of Phalaris arundinacea and achieved the replacement of dominant species.(4)During the period of fierce competition between Phalaris arundinacea and Phragmites australis,with the increase of allelopathic intensity,C of Phalaris arundinacea leaves and stems increased to varying degrees,and C of roots decreased;N,C:P and N:P of various components continued to increase;C:N continued to decrease.These results indicated that Phalaris arundinacea changed the nutrient utilization strategy of its components to alleviate the allelopathic stress under low allelopathic intensity.The content of N and P in the roots of Phragmites australis decreased,but increased in the stems and leaves;the C:P and N:P(except for the root C:P and the leaf N:P)of each component decreased to varying degrees.These results indicated that the nutrient content and ratio of each component also changed during the competition of the Phragmites australis,and it was in line with the"growth competition strategy"in ecological stoichiometry.