Effects Of Non - Biological Environmental Factors Regulation On Ecological Restoration Of Submerged Plants

Wetland protection and restoration is one of hot issues in the word, among which therestoration of submerge plants is an important way to achieve it. Research on the system ofwetland ecology has been a focus in this field, while less is about the influences of abioticfactors on the growth of submerged plants. Three kinds of submerge plants often used inwetland researvation in middle and lower Yangtze River: Myriophyllum spicatum L.; Elodeanuttallii（Planch.） H. St. John.; Vallisneria natans（Lour.）Hara are chosen in this studyto understand the influences of abiotic factors such as sunlight, nutrition, water level, CO2andtemperature on the growth of submerge plants. The influences of abiotic factors variation onmorphological variation，biomass，clone number and physiological index are studied. Thefindings are as follows:1. At a±100cm amplitude, the plants allocated more biomass to the roots and producedthe fewer and longer branches. Plant growth was promoted in high-nutrient sediments at a±50cm amplitude. The production of auto-fragments was increased in the high-nutrientsediments but significantly decreased by high water-level fluctuations. These findingsindicated that sediment nutrient levels and water-level fluctuations had strong effects on thegrowth and reproduction of M. spicatum and that increased sediment nutrient levels facilitatenutrient acquisition and promote plant growth and reproduction. For the restoration ofsubmerged macrophytes, moderate water-level fluctuations were highly desirable, particularlyin high nutrient habitats.2. The established M. spicatum and E. nuttallii bed had a positive effect on the seedrestoration of V. spiralis, but that the restoration efficiency was significantly reduced by thehigh-density (dense) cover of the elodeid community. The results indicated that the use of"nursery beds" with a certain density allowed for the successful reestablishment of stable SAVspecies and that future SAV restoration projects should focus more on a multi-speciesrestoration approach.3. The high level of underwater illumination compensation increased the survival rate ofV. natans seedlings, the total biomass of seedlings, the average biomass per plant biomass andthe number of clones (significantly increased25%,220%,150%and160%compared with thecontrol group, respectively). Through the underwater illumination compensation, V. natansincreased its seedling leaf number, leaf length and width, and this trend was enhanced withincreasing illumination intensity (high level of underwater illumination compensation groupsignificantly increased130%,100%and30%compared with the control treatment,respectively). Due to water turbidity, the control group decreased chlorophyll content in leavesand chla/chlb ratio. Through the underwater illumination compensation, seedling tissue SODand POD enzymatic activities of seedlings were also increased, indicating that the underwaterillumination compensation was unable to increase seedling leaves of reactive oxygen. Insummary, the underwater illumination compensation could promote the V. natans seedling survival, growth and physiological indexes. Therefore, the underwater illuminationcompensation system may be an effective submerged vegetation restoration method.4. During the60-day experiment, atmospheric CO2elevation significantly increased theinorganic carbon concentration in the water column. The warming systems elevated theaverage air temperature by3.0±0.5°C and the water temperature by2.0±0.3°C. Theelevation of CO2levels significantly enhanced the photosynthetic performance, growth andclonal propagation of V. natans. When combined with CO2elevation, elevated temperaturesalso promoted photosynthesis and growth performance. The individual plant biomass of V.natans increased with elevated atmospheric CO2levels but decreased under ambienttemperature elevation, indicating that plant body size would tend to decrease as a result offuture climate change. Atmospheric CO2elevation increased both stolon elongation and budnumber. At elevated CO2concentration, more biomass was allocated to the stolons, roots andbuds, whereas less biomass was allocated to the leaves. These results indicated that thephysiological and ecological responses of V. natans should increase its competitive ability andstatus in aquatic plant communities under future global climate change.