Water Hyacinth (an Invasive Plant) Grows Under Different Nutrient Levels And Its Impacts On Native Aquatic Plants

In recent years, water hyacinth (Eichhornia crassipes (Mart.) Solms), a noxious invasive species, infests most of lakes and rivers in southern China not only due to its extraordinary adaptive ability and clohal growth, but also deterioration in ecological environment and eutrophication in surface water. Performed studies showed that water hyacinth is a C₃ plant, but its growth rate is higher than C4 plants. This can be explained by whether other resources (such as nutrient) supply amply or not. When environment condition is feasible, water hyacinth will grow rapidly covering all water surface and being the dominant. Submersed plants are died for changed environments, living space of floating plants is minished, biodiversity is largely reduced, and thus the value of wetland protection and ecological service are directly affected, which are all as a result of the water hyacinth bio-invasion.In this study, we implemented a series of pot experiments to investigate the growth characteristics of water hyacinth at three different nutrient levels, and its competitive effects and mechanism on two native plants Ludwigia peplpoides ssp. Stipulacea and Hydrilla verticillata. Our results showed that:The impacts of nutrient-availability in the environments on growth and clonal propagation were significant. Ramet number, height and total biomass increased with the level of nutrient supply. The number of ramets, height and biomass of water hyacinth significantly increased as the nutrient level increased. Morphological plasticity of its root is an important adaptive mechanism to acquire resource. Root length would be longer under low-nutrient condition. Nutrient-enriched water accelerated the growth rate and enhanced the propagation of water hyacinth, which resulted in reduced growth of Ludwigia peplpoides ssp. Stipulacea. and Hydrilla verticillata. Being supplanted by water hyacinth, biomass of Ludwigia peplpoides ssp. Stipulacea was deduced by 57 % and 73 % in level II and III. Hydrilla verticillata, a submerged plant, was restrained significantly for lack of light which is necessary for photosynthesis(p<0.01). Biomass of Hydrilla verticillata was reduced by 84.5 %, 81.3% and 77.7 % in level I, II and III.This result suggests that eutrophication further facilitates the invasion of this weed in water bodies and thus boosts the competitive advantages of water hyacinth over native plants. Therefore, alleviating water pollution is a key factor for controlling the spread of water hyacinth, and protecting native biodiversity and ecosystem function.