Analysis Of Temporal And Spatial Distribution Characteristics Of Aquatic Plants In Wuliangsu Sea Based On Landsat Data

Aquatic plants have functions such as adsorption and purification,improving lake water quality,inhibiting sediment suspension,inhibiting algae growth,and protecting fishery production,and play an essential role in lake ecosystems.With the continuous expansion of human activities,the continuous progress of production and life,the outbreak of the global population,and the long-term impact of pollutants from agriculture,industry,and life,Wuliangsuhai has experienced eutrophication,excessive growth of aquatic plants,and sedimentation.,causing lake water pollution and strong biological accumulation,resulting in lake swamping.Therefore,studying the dynamic information of aquatic plant taxa and its spatial distribution characteristics plays a crucial role in the restoration and management of lake ecology.In this study,based on the measured spectral data of Wuliangsuhai,the spectral characteristics of aquatic plants were analyzed,and an appropriate spectral index was constructed to distinguish emergent vegetation,submerged vegetation and floating zooxanthellae in the complex water environment of Wuliangsuhai.Based on Landsat TM/ETM+/OLI data,using spectral index and decision tree methods,remote sensing classification of aquatic plants in the Wuliangsu Sea from 1986 to 2018 was carried out,and their spatial and temporal distribution characteristics were analyzed.The main conclusions are as follows:(1)Based on the measured reflectance data and the Landsat-8 OLI data on August 14,2017,the spectral characteristics of the aquatic plants in the Wuliangsu Sea were analyzed,and the remote sensing classification of the aquatic plants in the Wuliangsu Sea was carried out by using the spectral index and decision tree methods.With information extraction,the classification results of aquatic plants were verified.The results show that the method proposed in this thesis has a high classification accuracy for the Uliangsu sea plants.(2)Interannual temporal and spatial variation of various aquatic plants in Wuliangsuhai.From 1986 to 2018,the overall growth trend of emergent plants was a tortuous growth first and then a rapid decline.(1)The tortuous growth stage(2)The rapid decline stage.The overall changes of submerged plants from 1986 to 2018 were twists and turns,which were basically divided into two stages:(1)a fluctuating decline stage(2)a rapid growth stage.From 1986 to 2018,the yellow moss algal blooms had no obvious regularity of change,but showed an explosive growth.Emergent plants are basically found throughout the entire lake;submerged plants are mainly found in the East Beach,the central open water area and the southern waters of the lake;the areas prone to yellow moss algal blooms are concentrated in the East Beach and around the wharf.(3)Temporal and spatial variation of various aquatic plants in Wuliangsuhai d uring the year.Emergent plants are basically the same as submerged plants from development to decline every year,and are divided into four stages:(1)budding d evelopment period(May-June);(2)stable growth period(July-August)(3)prosperous period(August-September)(4)recession period(October).The annual change rule of yellow moss algal blooms: generally begins to grow in mid-May,and June is the rapid growth period of yellow moss algal blooms.It generally breaks out in mid-July,begins to decline in early August,and gradually disappears in October.