| The dynamic distribution of aquatic plants can reflect changes in the ecological environment of water areas,and mastering the spatiotemporal distribution of aquatic plants is of great significance for the management and monitoring of lakes.Under the influence of natural factors and human interference,the living environment of aquatic vegetation has been seriously damaged,and the distribution area of vegetation has gradually decreased.Remote sensing has become an important technical means for monitoring aquatic plant research due to its advantages of wide range and high response.This study takes Donghu Lake as the research object,based on long-term Landsat image data,combined with normalized water body index,greenness index,and algae index,and using decision tree classification methods,constructs an extraction model of aquatic plants in Donghu Lake in Wuhan.The seasonal distribution map of emerging/floating plants and submerged plants in Donghu Lake in 2020 and the annual distribution map of31 periods from 1990 to 2020 are drawn,and the relationship between meteorological and water quality factors and aquatic plants in Donghu Lake is analyzed,The reasons for the dynamic changes of aquatic plants in Donghu Lake during the past 30 years were discussed.The main conclusions of this article are as follows:(1)The decision tree model can accurately obtain the distribution of aquatic plants in the Donghu Lake.By analyzing the spectral characteristics of emergent/floating plants,submerged plants,and water bodies,the characteristic spectral indices of different aquatic plants were constructed.Based on the CART decision tree algorithm,an extraction model for aquatic plants in the Donghu Lake was established.Upon testing,the overall accuracy of the model was 82.29%,and the Kappa coefficient was 72.39%.(2)The growth of aquatic plants in the Donghu Lake has seasonal characteristics.By analyzing the area changes of aquatic plants in the Donghu Lake in February,April,August,and October in 2020,it can be seen that aquatic plants begin to grow in spring,the growth area of aquatic plants in the Donghu Lake gradually expands in summer,the aquatic plants begin to decline in autumn,and the distribution area of aquatic plants in winter reaches the lowest point.(3)The spatial distribution of aquatic plants in the Donghu Lake changed significantly from 1990 to 2020.The changes in the area of aquatic plants in the Donghu Lake from 1990 to 2020 can be divided into three stages:the first stage(1990-1996)is that the growth area of emergent/floating plants first decreased and then increased,while the growth area of submerged plants continued to increase;In the second stage(1997-2015),the area of submerged plants and emergent/floating plants fluctuated significantly between years.During this period,the maximum area of aquatic plants in the Donghu Lake was 2.61 km~2,and the minimum area was only 0.49 km~2.Among them,the area of aquatic plants decreased significantly in 1998,2001,2003,2005,2006,and2010;In the third stage(2016-2020),the aquatic plants in the Donghu Lake gradually recovered,with the growth area of emergent/floating plants increasing by 30%,and the growth area of submerged plants increasing by 18%.In terms of spatial distribution,before 2011,aquatic plants in the Donghu Lake were scattered along the banks of various sub lakes.After 2011,aquatic plants in the Donghu Lake showed a large area of growth in patches.(4)Meteorological factors have a small impact on the growth of aquatic plants in the Donghu Lake,while water quality factors have a significant impact on the growth of aquatic plants in the Donghu Lake.Through analyzing the relationship between the growth area of aquatic plants and the annual average temperature and precipitation over the past 30 years,it was found that the correlation between the annual average temperature and precipitation and the aquatic plants in the Donghu Lake was relatively low.There are differences in environmental indicators between the distribution areas of aquatic plants and the distribution areas of anhydrous plants in the Donghu Lake.Total phosphorus,total nitrogen,water depth,transparency,and turbidity may all affect the growth of aquatic plants.Analysis of the causes of changes in aquatic plants in the Donghu Lake indicates that aquaculture,water quality changes,and artificial cultivation of aquatic plants are the main factors affecting the evolution of aquatic plants in the Donghu Lake. |
PDF Full Text Request