Distribution And Ecological Adaptation Characteristics Of Solidago Canadensis To Jiuduansha, Shanghai

Solidago canadensis is a newly-invaded plant and has spread rapidly inJiuduansha Nature Reserve, causing damage in local areas. In order to provide atechnical guidance for the integrated management of the invasive alien species, thepresent paper conducted researches in relation to population and community ecology,resistance physiology, reproduction biology, root system characteristic and otheraspects. The main results are as follows:（1） Based on data from the remote sensing satellite and the field investigation,the distribution characteristics and spread trend of S. canadensis in Jiuduansha wereelucidated. The results showed:①S.canadensis has spread rapidly within the twosurveyed years in the investigated areas;②S.canadensis mainly inhabited in thehabitats with higher hypsography along the tidal creek of all grades;③the distributionarea of S. canadensis in Shangsha, Zhongsha and Xiasha was0.4096,0.3392and8.6992hm², respectively, with a total area of9.448hm².（2） The morphological features of root parts of S.canadensis in different soiltypes, and their endurance abilities to submersion treatment with different times, andtheir adaptability to different community environments were studied. The resultesshows:①based on root length, area, volume, surface area, projection, the number ofroot tips, the root systems of S.canadensis collected from Jiuduansha were clearly notas good as those from Botanic Garden of Shanghai Normal University in their growthstatus;②the roots, rhizomes, roots and rhizomes of sections of S.canadensis fromJiuduansha are able to reproduce. Their vegetative abilities, however, varied muchamong different vegetative organs;③the population density of Phragmites australishas a great inhibitory effect on the survival of vegetative reproduction of S.canadensis.（3）1000-fruit weight of seed of S.canadensis, water content, the seed germination rates under different environments were determined, the results show:①the1000-seed weight of S. canadensis is0.046-0.051g, the average water content of seedsis about60-80%;②the seeds of S.canadensis have higher germination rate in thesolution with pH6.0-8.0, while lower in the solution with pH higher than10.0orlower than4.0;③the seed germination of S. canadensis was influenced by salinityconcentration to some extent, with a germination rate of5%even in the solution with21‰NaCl.（4）The chlorophyll fluorescence parameters of S. canadnesis at differentpopulation densities, the different light intensives, and infected by net stinkbug（Stephanitis sp.） were determined. We found that S. canadensis is a typical sunnyplant, easy forming high-density populations. In the adult individuals, the uppermature leaves have higher maximum photosynthesis rates, while the leaves on thebase or lower parts, and the young leaves on the top have lower photosynthetic rates,because these leaves are not at the best physiological conditions. The population of S.canadensis, as a whole, maintains high photosynthetic rate because of the medianleaves with higher photosynthetic rates.（5） The number and biomass of the survival individuals of S. canadensis under thepopulations of Phragmites australis with different densities were determined,revealing that Phragmites australis has allelopathic inhibitory effects on S.canadensis.（6） Under no NaCl stress, according to gross caloric values （GCV） from high tolow, the order ranked as leaves, inflorescences, stems, and roots of S. canadensis, theirGCVs being18.61,17.88,17.17and15.92kJ.g^-1, respectively. With the increase ofNaCl concentration in the treatment solution, the ash content in roots andinflorescences firstly decreased, and then increased, while that of leaves continuedincreasing. The gross caloric values of leaves and stems have negative relationshipwith their ash contents, revealing the leaves and stems of S. canadensis could reachrelative bigger physical body with lower energy, thus maintaining its competitionpredominance. The above characteristics of S. canadensis are good for its growth inthe habitats with high saline content in Jiuduansha.In summary, S. canadensis mainly inhabited in mesophytic environments withhigh topography along tidal creaks of various grades, especially the environments along tidal creaks of the first grade and second grade, attention should be paid suchenvironments in relation to the control of S. canadensis. Often in such environments,S. canadensis often grows with other weeds, without native species such asPhragmites australis and Scirpus mariqueter. Therefore, it is possible for us to applyherbicides to control S. canadensis, without influences on the native species. Exceptfor the habitats with high topography, most environments in Jiuduansha are oftensubmerged or influenced by the tide fluctuates, the roots of vegetative reproductionorgans of S. canadensis didn’t develop well, which make it possible for us to usesome portable manual mechanical equipment to remove S. canadensis. Theimmersion within short time could cause the vegetative reproduction organs of S.canadensis lose their vigor, in the future mechanical control of S. canadensis, theremoved roots and other vegetative reproduction parts should be immersed in thewater to prevent them reproduction and spread again.