Research on Competition of Elodea nuttallii with Myriophyllum verticillatum,Vallisneria natans and Ceratophyllum demersum

Four submerged macrophytes,Elodea nuttallii,Myriophyllum verticillatum,Vallisneria natans and Ceratophyllum demersum,were planted to observe the growth potentials and competitive abilities in outdoor 2m×2m pools.The areas of every species were 1.08m2.Results showed that from June to August,Elodea nuttallii grew fastest and its expansion ability was strongest.Its distribution area was 3.69m2 and the quantity proportion reached highest,76.59% in June.From July to September,Myriophyllum verticillatum had the advantage of canopy position,and floated on the surface.It could make full use of sunshine and its area reached 2.34m2,while its quantity proportion still increased,and reached the highest of 48.99% in October.At this period,Vallisneria natans grew in the middle and lower layer of the water body,meanwhile Elodea nuttallii degenerated because of heat and the lowest area reduced to 1.26m2.In autumn-winter and spring,because Elodea nuttallii had strong chillness-tolerance,its area increased to 3.20m2,which made it possess competition advantage in time and space,and directly affected competition pattern among the four plants.Overall,Elodea nuttallii occupied a distinct advantage in competition with native species,which should be paid attention to when introduced in northern China.