Study On The Ecological Adaptation Mechanism Of Solidago Canadensis L.

Solidago canadensis s.l. L. ?Canada goldenrod? is a perennial herb of North American origin that has been a cosmopolitan weed. Due to its special biology and ecology characteristics This species caused a series of hazards like biodiversity loses, severer economic loses and landscape destruction. This study began from the survey of S. canadensis communities including species and density in different invasion gradients, and carried out the further research about sexual and asexual reproduction,, allelopathy and impact on soil properties, etc, intended to explain the invasion of S. canadensis and provide a theoretical basis for controlling.1.The surveys of species and density on different gradients of S. canadensis communities.In this study, we used sampling method for species and density surveys nd analyzed the species diversity index within different invaded gradient. The results showed that:?1? With the deepening of the invasion, the types and relative density of native species in invasion area are induced, there are 20 kinds of native plants in mild invasion communities, the relative density of S. canadensis is 0.057; in severe invasion areas, there are only 6kinds of native plants, the relative density of S. canadensis is up to 0.690; ?2? The invasion of Solidago canadensis reduced the diversity on invaded area. The Shannon-Wenner index in mild invasion area ?2.67±0.28? is higher than severe invasion area ?0.93±0.81?, it turns out that there are significant differences in diversity index between different invasion gradient communities.2.Through the study of sexual reproduction Solidago canadensis showed:?1? Seeds generated in different parts of inflorescences have different seed vitality, the thousand kernel weight ?TKW? of the seeds produced by lower part of inflorescence is 50.41mg. Solidago canadensis has high seed germination rate which is larger than middle and upper parts; the average seed germination rate of lower part is 65.8%, which is significantly higher than middle and upper parts, there is a significant difference between the various parts of seed germination ?P=0.05?; ?2? The average germination rate and germination index of Solidago canadensis seeds were 61.00% and 20.23, the germination rate of the other two kinds of compositae plants dandelion?Taraxacum mongolicum? and Youngia japonica were 38.80% and 51.00%, the germination index were 8.54 and 7.33. Compared with these two kinds of compositae, the seed vigor index of S. canadensis is large, and the germination rate and germination index are significantly different.3.Through the experiment of asexual reproduction of Solidago Canadensis L. showed:?1? Manually cutting interference can facilitate cloning reproductive capacity of aerial stem. With the height of the remaining increased after cutting off, the newborn branches of remaining part increased. Newborn number of branches are 9.5 when remaining height is 130cm, and after the other cutting interfere, the newborn branches are also more than 4; ?2? Manually cutting interference caused the biomass allocation changes of S. canadensis. Under natural conditions, Solidago canadensis allocation of roots, stems, leaves and flowers were 0.145,0.491,0.209 and 0.155. After manually cutting interference, S. canadensis invest more to sexual reproductive organs and less to root and stem organs, the average proportion of the investment to sexual reproductive organs is more than 0.21. Before and after manually cutting interference, S. canadensis biomass allocation has significantly difference.?3?The underground stem of Solidago canadensis has strong ability of asexual reproduction. With the increase of buried depth, number of shoots of gemmas on the underground stem of Solidago canadensis decreases, and as the number of gemmas on the underground stem of Solidago canadensis reduced, the germination rate in lower. In the treatment of the buried depth is 3cm and 15cm, the number of shoots of underground stem of Solidago Canadensis that contains 3 gemmas is 7.2 and 4.6, respectively, the number of shoots of underground stem of Solidago Canadensis that contains 1 gemma is 2.4 and 0; With the increase of buried depth, initialized number of days of underground stem of Solidago Canadensis was increased. The initialized number of days of underground stem of Solidago Canadensis in the treatment that the buried depth is 3cm and 15cm is 6.4th day and 30.2th day.4.Using the different concentration extract of S. canadensis to deal with seed germination experiments of tomato ?Lycopersicon esculentum Mill?, Chinese little greens ?Brassica chinensis var chinensis? and ryegrass ?Lolium perenne L.?, and measured in final germination rate, germination index and germination trend. The results showed that:?1? Solidago canadensis exists allelopathy; ?2? the different concentration extract of S. canadensis had a definite inhibitory effect on the growth of this three kind of seed, and the higher the concentration, the stronger the inhibitory effect.5.Determination of soil physical and chemical properties of different gradients Solidago canadensis invaded region, the results showed that:?1? With the deepening of invasion, soil moisture content on the rise,,the soil water content in severe invasion area was 0.24, increased about 20% than no invasion area, which prove that Solidago canadensis invasion may increase water-holding capacity of soil; ?2? Solidago canadensis invasion reduced the soil nutrients on invasion area, which inhibiting the growth and development of native plants.6.Through the experiment of chlorophyll relative content and diurnal changes of photosynthesis of the leaf of different parts of Solidago canadensis L. showed:?1? The chlorophyll relative content of the leaf of different parts of Solidago canadensis L. is difference, the value of chlorophyll relative content about the middle blade is 37.29±0.884SPAD, it's the highest value. ?2? The trend of diurnal changes of photosynthesis about leaves of different parts of Solidago canadensis L.is difference,the photosynthesis of central leaves is best, the highest magnitude of the photosynthesis of central leaves is 21.176?molCO₂·m-2·S-1 The upper leaf and central leaf photosynthesis in lunch break phenomenon. The diurnal changes of photosynthesis of the bottom leaves appeared as single peak, and the photosynthesis of bottom leaves the is weak, the highest magnitude of the photosynthesis of bottom leaves is 16.688?molCO₂·m-2·S-1.