The Temporal And Spatial Variation Of Suaeda Salsa In Liaohe Estuary From 1997 To 2018

The Liaohe Estuary coastal wetland is one of the important estuarine wetlands in northern China.The unique Suaeda salsa grows in its territory,forming a unique"red beach"landscape.The Suaeda salsa is an important pioneer and dominant vegetation in the Liaohe Estuary coastal wetland,which plays a vital role in the Liaohe Estuary coastal wetland ecosystem.However,due to the influence of various factors,the growth of Suaeda salsa in the coastal wetland of Liaohe Estuary coastal wetland has declined rapidly in recent ten years.The main data source of this research was based on the Landsat remote sensing images from 1997 to 2108,and the field investigation data.In order to extract the information of the Suaeda salsa,this research was using the Artificial Neural Networks(ANN)and visual interpretation by making full use of the characteristics of Suaeda salsa.According to the spatial and temporal distribution characteristics of Suaeda salsa in the past 22 years,combined with the landscape index,quantitative analyzing the tempor-patial distribution of Suaeda salsa.The results are as follow:(1)The method of wetland vegetation information extraction and dynamic monitoring based on remote sensing image can effectively analyze the characteristics and laws of annual change of Suaeda salsa.The best season for the monitoring of the Suaeda salsa is autumn.(2)The Suaeda salsa in the study area gathered and grew in strips or blocks along the coastline,and had a trend of migration to the Sea along the coastline.(3)From 1997 to 2018,the total area of Suaeda salsa in the study area had been reduced by 12.79km~2,including a stable growth stage(from 1997 to 2001),three rapid extinction stages(from 2001 to 2005,from 2008 to 2010,from 2014 to 2016)and three slow recovery stages(from 2005 to 2008,from 2010 to 2014,from 2016 to2018).The overall area of Suaeda salsa showed a declining trend.(4)From 1997 to 2018,the plaque area of Suaeda salsa in the study area was significantly reduced,and the plaques were seriously broken.There were three processes from large plaque aggregation to small plaque dispersion growth(from1997 to 2005,from 2005 to 2010,from 2010 to 2018),the community showed a tendency to shrink and degenerate.(5)From 1997 to 2018,the Suaeda salsa community in the study area was unstable,the degree of landscape fragmentation increased,the degree of landscape dominance decreased,and the degree of disturbance caused by human activities increased.