Seasonal Growth And Resources Allocation Dynamics And Competition Research In An Invasive Species,Eichhornia Crassipes

Water hyacinth(Eichhornia crassipes(Mart.)Solm.),native to South America,now has invaded many place in the world and has been considered as one of the world's worst nuisance aquatic plants and E.crassipes had been introduced into China in the last century and soon broke out in many water areas,such as rivers,lakes and so on.The invasion of E.crassipes caused huge harm to the local aquatic ecosystem.In this paper,the seasonal morphology traits,biomass and biomass allocation,physiological traits of E.crassipes,in addition,the effects of flood disaster on the population of E.crassipes were studied in Liangzi lake area,aiming to exploring the potential physiological weakness point of E.crassipes and the adaptation strategy to extreme environment.At the same time,we compared the competitive relationship between E.crassipes and Pistia stratiotes,to explore the potential similarity between the two invasive species.The main results are as follows:1.The traits of morphological,biomass and physiological of E.crassipes varied with the seasons.Population density continued increasing significantly before July to about 250 plant m-2,and then maintained relatively stable;The relative clonal rate(0.025 plant plant-1 day-1)and relative growth rate(0.035 g g-1 day-1)of the E.crassipes population were highest at the beginning of the growing season,then decreased gradually with the advance of time and negative growth occurred at the end of the growing season.Individual biomass and population biomass of E.crassipes gradually increased and peaked in November,about 7.12g plant-1 and 1900 g m-2 respectively.About 90%population biomass was concentrated in the aboveground part and at the same time about 84%biomass was distributed in vegetative growth.Mean chlorophyll content was about 1.74 mg g-1 and chlorophyll a/b values fluctuated between 2 to 3;Stembase,whose starch content reached maximum(308.4 mg g-1)before death,was the key to E.crassipes overwinter and regrowth in next year.There maybe two potential physiological weakness point in the growth cycle of E.crassipes according to the change of carbohydrate content:One was the early stages of growth cycle,when young plants begin to appear and clone quickly,and the total nonstructural carbohydrate(TNC)content of stembase was lower;the other was October and December,during which carbohydrates were accumulated quickly in stembase.2.Flooding had great effects on population of E.crassipes,which significantly reduced the plant height,population density,aboveground biomass and carbohydrate content.However,E.crassipes can alleviate the disturbance of floods and recover growth rapidly after the flood by increasing the proportion of resources invested in the underground part.3.The relative growth rate(RGR)of E.crassipes was similar with P.stratiotes when planted separately.The individual biomass of E.crassipes was larger,but the relative clone rate and the yield per plant of P.stratiotes was higher.The competition balance index(CBI)of E.crassipes was 0.87 when planted mixed,and at the same time it significantly reduced the relative clonal rate,relative growth rate and yield per plant of P.stratiotes,which indicated that E.crassipes had a competitive advantage compared with P.stratiotes.