Study On The Ecological Of Sparganium Angustifolium Michx In North Temperate River

Submerged macrophytes are an important part of aquatic ecosystem.The study of their growth and reproduction strategies can provide technical support for the diversity protection and phytoremediation of submerged vegetation.Aquatic plants are affected by biological or abiotic factors in the process of growth and reproduction.Therefore,aquatic plants will show diversified ecological adaptability to different habitat conditions.However,little research has been done on the response of aquatic clonal plants to habitat conditions.Thus,we choose typical aquatic clonal plants of S.angustifolium in cold temperate zone as the research materials.Field investigation and controlled experiments were used to study the reproductive strategies,clonal plasticity,foraging behavior and defense strategies against invasive species of S.angustifolium in different life stages.The first part of the paper mainly focuses on the reproductive mode of S.angustifolium.Firstly,field investigation showed that under natural habitat conditions,the number of seedlings germinated by sexual reproduction was higher than that by asexual reproduction in the same period,but there was no significant difference in plant height and biomass of germinated seedlings.Among all the indexes of water environment,water level and water velocity have the greatest influence on the germination number,biomass and plant height of seedlings of two reproductive modes.Then,through the control experiment “The influence of environmental factors on S.angustifolium sexual reproduction”,we found that: water level,temperature and distribution depth have great influence on the germination rate of S.angustifolium seeds,among which the fluctuation of water level and temperature in different degrees are beneficial to germination,while the distribution depth is negatively correlated with germination,while the nutritional gradient has no significant effect on the germination rate of seeds.The second part of this paper focuses on the plastic response of S.angustifolium to environmental disturbances during their growth period.Firstly,the field survey showed that,with the change of time,submerged life style increased their investment in the underground part in the two water forms of natural environment(running water and standing water),but their total biomass was lower than that of emergent life style.With the increase of water level,both submerged and emergent life style not only increase the allocation of underground resources,but also significantly increase the plant height.In the same water depth,the plant height and belowground biomass of emergent life style are higher than those of submerged life style.Although the number of clonal ramets of submerged life style decreased with water depth,it was significantly more than that of emergent life style.Then,two experiments were carried out,“The growth performance of S.angustifolium in different heterogeneous soil type and water depth environments” and “The clonal plasticity of plants in different hydrological habitats”: compared with the homogeneous soil nutrient substrate,the heterogeneous soil nutrient substrate did not play a positive role in plant growth,and the biomass accumulation of S.angustifolium in the two heterogeneous substrate was significantly different.When S.angustifolium are stressed by high water level,they will invest more in the aboveground parts to obtain light resources.Sexual reproduction is blocked at high water level,and asexual reproduction is still the main reproductive mode.Compared with standing water,S.angustifolium in running water produce more ramets and longer stolons,and form streamlined leaves.These morphological structures can alleviate the pressure of water flow.Moreover,S.angustifolium increase the allocation of underground resources(biomass,clonal ramets,etc.)and these plasticity improves the fixation ability of plants in running water habitats.Two experiments “The reproductive strategies of S.angustifolium to simulate temperature rise and water level gradient” and “The resistance strategies of plant populations to invasive species” were carried out to find out: with the increase of water level,plant height was significantly affected;however,under warming conditions,its asexual reproduction dominated,the number of clonal ramets and the investment of biomass in each part of clonal ramets increased,whereas the seed biomass of sexual reproduction gradually decreased.Under low water level,compared with submerged and emergent invasive plants,floating invasive plants(Eichhornia crassipes and Pistia stratiotes)have a significant impact on plant growth and reproduction by occupying the upper niche of the water body.Therefore,S.angustifolium mainly capture light and nutrient resources through clonal growth in horizontal direction,and plant populations have strong resistance to invasive plants of other two life forms.In conclusion,different environmental factors,biological factors and species characteristics determine that S.angustifolium show different reproductive patterns and morphological characteristics in the face of habitat heterogeneity.In the face of environmental disturbance,plant growth and reproduction strategies are mainly produced by increasing the proportion of asexual reproduction and adjusting the proportion of biomass allocation.