Growth Responses Of Elodea Nuttallii And Hydrilla Verticillata To Different Substrates And Studies Of Inter-specific Competition

Elodea nuttallii and Hydrilla verticillata are very similar in morphology and growth mode. Their growth responses to substrates with different fertilities and their competitive relationship were studied in controlled tank experiments. A replacement series experiment was set up to evaluate their competitive ability at two levels of soil fertility, and a year-round experiment was carried out to investigate the long-term competitive result of E. nuttallii and H. verticillata when they were grew together. The results are as follows:1. Sediments play an important role in nutrition supply for the growth features of the two submerged macrophytes, E. nuttallii and H. verticillata, such as their morphological structure, biomass accumulation and resource allocations which were significantly affected by sediment fertilities. Both species preferred to higher fertility. E. nuttallii and H. verticillata could show some phenotypic plasticity such as morphological traits, biomass allocation and nutrition allocation to adapt to different sediments.2. The year-round experiment found that E. nuttallii had higher cold resistance and could grow unceasingly in winter and earlier spring. Fragment branches is the only vegetative propagule that E. nuttallii depends to renew and expend its population. This character makes E. nuttallii have competitive advantages over H. verticillata in terms of time and space during winter and spring, and eventually replaced H. verticillata.3. In the short-term experiment, both E. nuttallii and H. verticillata grew vigorously. However, H. verticillata acquired competitive superiority over E.