Warming And Nitrogen Deposition Affect The Invasiveness Of Solidago Canadensis

Attracting broad attention, global changesare deeply influencing the ecologicalenvironments on earth that human live by and subsequently caused a series ofenvironment problems. Global warming, nitrogen(N) deposition and plant invasion arethe most important parts of global changes, while global warming and nitrogendeposition may change the characteristics of habitats, resource dynamic and speciesdistribution, thus changing the pattern of plant invasion. However, different warmingscenarios such as day-warming and night-warming may play different roles, and differentlevels of N deposition do exist in different area. What’s more, species of diverse life-formmay differently respond to warming and N deposition or it may even lead to differentresults studying their effects on invasion from different scale.Solicago canadensis is one of the most serious invasive plants around the area ofYangtze River delta now and will expand to the inland under the condition of globalchange. Researchers both from home and abroad extensively studied the distributiondynamics, reproductive characteristics and invasion mechanisms, but few evaluated itsinvasiveness under global change conditions such as warming or N deposition. As themost important limiting factors of growth, changes in temperature and N level may affectthe invasiveness of Solidago canadensis and result in different competitive ability withnative species. By using the infrared heater and NH4NO3to separately simulate warmingand N deposition, we identified the responses of Solidago Canadensis to differentwarming scenarios at the individual level in the first experimint, and then compared itwith the performance of an annual invasive plant Bidens pilosa. In the second experiment,we used the microcosm method to compose an artificial community and test the influenceof daily-warming and N deposition on the invasiveness of Solidago canandensis and testthe Evolutionary Increased Competitive Ability Theory(EICA) under the background ofwarming and N deposition. The main results were concluded as follows:1. In the individual level, daily-warming showed most significant influence onSolidago Canadensis, followed by day-warming and night-warming. In contrast, none of the three warming treatments significantly influenced the plant height and total biomassofBidenspilosa. Waming increased the above-ground biomass of both two species,decreased the below-ground biomass of Bidenspilosa but showed no effects on thebelow-ground biomass of Soliadagocanadensisi, resulting that root-weight ratiodecreased in both of the two species. There was a significant negative correlationbetween total biomass and root-weight ratio of S. canadensis; in contrast, root-weightratio is significant positively correlated with total biomass of B. pilosa. The resultsindicated that responses to waming were species-specific, plants of different origin andlife-form will respondsdifferently to warming for their inherent characteristics, and thisdifference depends on different warming scenarios. Warming may enhance theinvasiveness of Solidago canadensis by enhancing its growth and stress-tolerance, but itmay not be the truth under community competition for that the potential height, densityor biomass may not realize, or even inhibit its growth.2. N addition significantly increased the height and population density of Solidagocanandensis, and this effect was more obvious on Solidago canandensis from NorthAmerica than that of China. More specifically, N addition let Solidago canandensis fromNorth America had a greater leaf dry mass, leaf area, and leaf tissue density as well as asignificantly decreased specific leaf area while it let Solidago canandensis from Chinatend to have a a greater leaf dry mass and leaf area, but didn’t significantly affect thespecific leaf area and leaf tissue density. High level of leaf N content and efficient N usestrategy may play a key role in its invasion.3. The interaction effect of warming and N addition only affect the leaf dry mass andspecific leaf area of Solidago canandensis from North America, while had no impact onother indexes.4. Solidago canandensis from China had higher plant height, population density, leafarea and annual growth of plant height and population than Solidago canandensis fromNorth America with or without completion with native species. Both of the twopopulation exhibit stronger competitive ability when growing with native populationfrom China. Solidago canandensis from China out-performed Solidago canandensis fromNorth America when they separately competed with native species of China and NorthAmerica.5．The relationship between plant height and stem diameter of the two SolidagoCanadensis population meet different regression model, suggesting that there wastrade-off in the growth of plant height and stem thicknessin these two different provenance of Solidago Canadensis. Solidago canadensisfrom China would allocate lessenergy to stem thickness growth and defence,of which verifyingthe EICA hypothesis.