The seed germination and growth characteristics of introduced plant Betula nigra in hydro-fluctuation belt of three gorges reservoir area.
[Purposes] In order to scientifically evaluate the adaptability of introduced plant Betula nigra in hydro-fluctuation belt of Three Gorges reservoir area, the germination and growth characteristics of B. nigra seeds were observed. [Methods] Betula nigra seeds were sowed two times in the Rangdu town of Wanzhou district, Pengxihe wetland nature reserve of Kaizhou district, Shibaozhai town of Zhongxian county, Zhuyihe of Fengjie county in Chongqing city. The effects of different soil types and elevation on the seed cumulative germination rate and survival rate were studied. Plant height, ground diameter, crown width, flowering and fruiting were investigated, photosynthetic parameters were measured. [Findings] (1) B. nigra's seed germination under different soil conditions was different. (2) The survival rate of Betula nigra after seed germination was high, but all died after flooding. (3)Biennial seedling of B. nigra bloomed after two-year growth, but the number of flower and fruit was small. There's no seed germinated and no plants grew after the fruit dropped. The height of B. nigra which planted on the hydro-fluctuation belt of elevation 170 m and 175 m was 6.22 m, 6.95 m after four-year growth. There was a significant difference (p < 0.05). (4) The daily mean net photosynthetic rate of B. nigra at the elevation of 170 m increased gradually after outcrop in spring. It can increase up to 23.10 μmol m-2.s-1 in storage period in autumn. It was significantly higher than it in the elevation of 175 m (14.64 μmol.m-2.s-1) (p < O. 05). [Conclusions] B. nigra's individual species can't grow naturally. Introduced plant B. nigra which planted on the hydro-fluctuation belt of Three Gorges reservoir don't have ecological invasion by preliminary judgment. The length of flooding time in winter has a significant influence on the growth of B. nigra. But B. nigra can enhance photosynthesis ability to compensate the long-time effects of flooding on plant growth and finally it can adapt to the special environment of the anti-season flooding in hydro-fluctuation belt of Three Gorges reservoir area.