A Comparative Study On The Growth Characteristics Of Invasive Solidago Canadensis Under Warming And Nitrogen Addition

Global changes have received more and more attention along with increasingly intensified human activities since the industrial revolution.Two of these,global warming and atmospheric nitrogen(N)deposition strongly affect the metabolism of various organisms and ecological environments from various spatiotemporal scales.Global changes may aggravate risks of alien plant invasion.Invasive plants usually have broad physiological and ecological tolerance and plasticity,and changes in temperature and soil N availability could endow huge competitive advantages to invasive plants.Solidago canadensis,a worldwide invasive weed which is native to North America,has invaded coastal provinces in southeastern China and is expanding towards inland areas.With a strong reproductive ability,S.canadensis can form near or complete monoculturds in invaded habitats,which affects the connections among various functional groups,ecosystem structure,and biodiversity.Most studies on S.canadensis all over the world have focused on its characteristics of agamogenesis,allelopathy and interactions between soil and soil microorganisms,but little is known about how global changes influence its invasiveness.I conducted artificial communities through "microcosms" and grew S.canadensis from North America and China.I used an infrared heater and NH4NO3 to simulate 2?warming and 4 g m-2 yr-1 N deposition,respectively.The experiment has lasted for five years and we determined leaf traits,growth characteristics,resource allocation,and phenophases to study the interannual variability of invasiveness of S.canadensis from two different sources under warming and N addition.The main conclusions are as follows:(1)Compared with the S.canadensis from North America,Chinese counterparts had a smaller leaf dry matter content(LDMC),specific leaf weight(SLW)and chlorophyll content(CC),and slightly longer leaf lifespan(LL).After warming,S.Canadensis had smaller LDMC and SLW,longer LL and an unaltered CC.After N adding,S.Canadensis had unaltered LDMC and SLW but longer LL and higher CC.The influence of warming was manifest for S.canadensis from North America,and Chinese plants showed stronger adaptability to warming.Nitrogen adding could strengthen the effects of warming on leaf traits of plants from North America.In short,leaves of S.canadensis from China had stronger ability to access resources,and warming and N improved this ability.(2)Compared with the S.canadensis from North America,Chinese plants were higher but slighter,and there was no difference in tillers between two different sources.The tiller number was significantly increased by warming,but a slight decrease in plant height appeared,and the relationships between plant height and stem diameter were similar.After N adding,S.canadensis had higher plant height and more tillers,but the relationships between plant height and stem diameter were unaltered.The growth and proliferation ability of S.canadensis had interannual changes.The influence of N adding was manifest for S.canadensis from North America,which was along with the local climate.In short,S.canadensis from China had stronger ability to grow and proliferate,and warming and N addition improved this ability,which was influenced by inter annual climate.(3)Compared with S.canadensis from North America,the phenophases of Chinese plants were later.Warming and N adding did not affect the phenological periods of S.canadensis overall.Along with the accumulation of years,the gap of phenophase of S.canadensis from two sources has a tendency to shorten.The impact of warming and N on the phenophase of S.canadensis had interannual changes along with the local climate,and mostly on the S.canadensis from North America.In short,the phenophases of Chinese plants were later than those of S.canadensis from North America.Compared to the interannual climate,warming and N adding in this experiment would not be enough to affect the phenophase of S.canadensis.Chinese plant showed stronger adaptability to climate change.In summary,warming and N improved the invasiveness of S.canadensis.Chinese plants showed strong invasiveness and ability to adapt to the environment,and the invasiveness of S.canadensis from North America had a tendency to increase along with the accumulation of years.The global warming and atmospheric N deposition in the future are likely to aggravate the invasion of S.canadensis.