The Reproductive Characteristics Of Solidago Canadensis Under Simulated Climate Warming And Atmospheric Nitrogen Deposition

The scientific assessment and analysis of the current morphological plasticity of introduced ornamental plants and their possible morphological changes in the future are important countermeasures to prevent plant invasions during landscape plants introduction.Increasing global warming and atmospheric nitrogen（N）deposition are likely to change the reproductive patterns,reproductive phenology,and reproductive behavior of introduced species,allowing them to form different reproductive characteristics.Solidago canadensis was originally introduced into China as an ornamental garden flowering plant,and little is known about its reproductive ecological under climate warming and N deposition.In this thesis,I selected S.canadensis as a focal plant,simulated 2℃warming and 4 g m^-2 yr^-1 N deposition using an infrared heater and NH₄NO₃,respectively.Long-term monitoring tests were conducted from 2013-2018,I determined its asexual reproduction,reproductive phenology,and germination characteristics to address the reproductive ecological characteristics of S.canadensis under simulated climate warming and N addition;provided references for the application of S.canadensis and the introduction strategies for future garden plants.The main results were as follows:（1）The tiller number of S.canadensis was significantly increased by warming,but plant height and diameter followed the opposite direction.Nitrogen addition had no significant effect on the tiller number,plant height and diameter of S.canadensis.Over the six years（i.e.2013-2018）,the number of tillers of S.canadensis showed a gradual increase,and its plant height showed a trend of a decrease first and then increase.The plant height and tiller number of S.canadensis in different years were decreased and increased by warming,respectively,and these decreases and increases were most obvious in 2018,respectively.It could be concluded that S.canadensis might occupy a larger space position and devote more resources to its asexual reproduction with time,and warming might enhance its ability.（2）The first budding date,flowering date and fruiting date of S.canadensis were delayed by warming.Nitrogen addition advanced the fruiting pate of S.canadensis.From 2014 to 2018,the budding date and flowering date of S.canadensis showed a gradual delay,while the fruiting showed a gradual advance and the death showed a trend of first delay and then advance.Warming delayed the fruiting of S.canadensis,and this delay was mostly significant in the absence of N addition.Warming delayed the budding date of S.canadensis in different years,and the delay was the most significant in 2018.The effect of warming on the delayed flowering of S.canadensis in different years was manifest in the absence of N,and was most significant in 2018.It could be concluded that the reproductive phenology of S.canadensis might be delayed over time,its duration of reproduction might be shortened,and climate warming might increase the ability of former,and N addition might promote the ability of the latter.（3）The germination rate of seeds from plants grown under warming conditions was significantly lower than that of seeds from plants grown under ambient conditions.The seed germination characteristics of different populations of S.canadensis were significantly different.The seed germination rate of the 29^th non-warming S.canadensis population was 82.7%.It could be concluded that the seeds from different habitats and populations have different germination strategies to complex environments.In conclusion,the asexual reproduction ability,reproductive phenology,and germination rate of the seeds of S.canadensis were enhanced,delayed,and decreased by warming,respectively.The effects of warming on the asexual reproduction and reproductive phenology of S.canadensis were more significant with the accumulation of years.Nitrogen addition shortened the reproductive duration of S.canadensis,and alleviated the delay of warming on the reproductive phenology.In the context of future climate warming and atmospheric N deposition,S.canadensis might devote more resources to its asexual reproduction and few resources to its reproductive phenology and seeds.