The Reasons for the Degradation of Aquatic Plants in the Caohai Lake Area of Guizhou

Guizhou Caohai Wetland, as an important plateau wetland in the country, has lost its aquatic plants due to changes in ecological factors such as water environment. We compared the characteristics of soil seed banks under different water level conditions and studied their correlation with soil and water environmental factors. We found that there were differences in the number of plant seeds, species diversity, and life forms and histories in soil under different water level conditions. The area with a water level of ≤ 50cm has the highest number of plant seeds and species, with a total of 22 species, 2759 seeds/m2,45% of perennial submerged plants,32% of perennial aquatic plants, and 23% of annual submerged plants.Water level of 100cm-150cm has the lowest number of seeds in the soil, with only 196 seeds/m2.Correlation analysis indicates that the number of plant seeds and species diversity in the soil are significantly negatively correlated with soil pH, moisture to dry ratio,organic carbon,organic matter,total nitrogen,nitrite nitrogen, available potassium,Mg2+,CO3-,SO42-,HCO3-,Cu,Ca,Zn, Mg.The number of seeds is significant negative correlation with oxidation reduction potential, alkalinity, chemical oxygen demand of water.Species diversity is significantly negatively correlated with ammonia nitrogen.Redundancy analysis identified that the change of water level have a significant impact on K+,Ca2+,oxidation reduction potential,Cl-,SO42-,HCO3-,moisture to dry ratio in soil, and dissolved oxygen, temperature,ammonia nitrogen, total phosphorus, total dissolved solids,alkalinity,oxidation reduction potential, chemical oxygen demand in the water environment.The environmental changes caused by hydrological differences are the key factors affecting the soil seed bank in the Caohai Lake area. There are difficulties in using the soil seed bank to achieve natural recovery of plants such as Schoenoplectus tabernaemontani, Ceratophyllum demersum, Potamogeton crispus, Ottelia acuminate, Nymphoides peltate in the Caohai Lake area.It is necessary to adopt various methods for comprehensive restoration and treatment, such as controlling sources and intercepting pollution, improving water quality, regulating hydrological rhythms, and artificial planting.