Biological traits and competition mechanism of Vallisneria natans in the mining subsidence area

The mining subsidence wetland has obvious characteristics of dynamic, high ground-water level and ecological frangibility. Exploring the biological characteristics and competition mechanism of artificially constructed aquatic plant community is beneficial to recover aquatic vegetation in mining subsidence wetland. This study takes the dominant species of Vallisneria natans as an example to analyze its biological traits and competition mechanisms in Panji District of Huainai City by means of field survey and sampling quadrat investigation. The results showed that V. natans in subsidence area have same biological characteristics (reproductive pattern, pollination mechanism and life history) as plants in shallow lakes, but sexual reproduction was the dominant reproduction way for V. natans in study area. V. natans could grow with current-year Ass. Typha angustifolia community with low biomass; however, V. natans has a competitive disadvantage with two or more years Ass. T. angustifolia community and V. natans would gradually disappeared when coverage of T. angustifolia was ≥90%. V. natans had poor competitiveness with floating plant Ass. Nymphoides peltatum and Ass. Marsilea quadrifolia in mining subsidence area with coverage, plant height and biomass decreasing. V. natans also had poor competitiveness with submerged plants Ass. Potamogeton malaianus while could coexist well with Ass. Hydrilla verticillata, Ass. Myriophyllum verticillatum, Ass. Najas marina, and Ass. Ceratophyllum demersum by inhabiting different water layers. In conclusion, V. natans have obvious competition advantages at the aquatic plant community in identical water layer with similar growth form, while poorly compete to plants with different growth form, especially emerged plants and floating plants.