Dynamic Monitoring And Driving Factors Of Phragmites Australis Wetland In Bosten Lake

The survival,reproduction and development of mankind are closely related to the wetlands.Wetlands provide a variety of resources for mankind,they not only have the huge environmental functions,but also have other ecological roles that can not be replaced by others.It is known as "the kidney of the Earth" as the transition between water and land.As an important natural resource and constructive species of wetland phytobiocoenose,the Pragmitesaustralis has a self-regulation role on purification of wetland,water balance and regulation of the local microclimate.In recent years,wetlands are shrinking and degrading in function due to the gradual warming of the global climate,population growth,blind reclamation,transitional emissions of pollutants and other reasons.As a result,human survival environment is being threatened.Solving the problem of dynamic monitoring of wetlands and the driving force analysis which leads to their changes is a prerequisite for the protection of wetland resources.In this study,based on 27 years(1990 – 2016)of Landsat interpretation data,combined with meteorological and hydrological data,the temporal and spatial variation trends of Pragmitesaustralis wetland within 1050 m of contour line were studied using linear regression model and generalized linear model.Main driving factors of spatio-temporal variation of reeds wetland were analyzed.Result shows that:(1)the area of Pragmitesaustralis around the Bosten Lake shows different variation trends in two stages of period,before and after 2000.Comparing two different part of Lake,significant variation trends can be found in main Lake,the area of Pragmitesaustralis shows decreasing trends from 1990 to 2000 and increasing trends from 2000 to 2016.The main driving factor for this variation trends is the water level.The area of Pragmitesaustralis was negatively correlated with water level.(2)Unlike with the main Lake,the variation trend of Pragmitesaustralis in small Lake is unremarkable.From 1990 to 2000,the area of Pragmitesaustralis wetland was increased with fluctuations,but increasing trends is not considerable.From 2000 to 2016,remarkable increasing trends with fluctuations can be found.The main driving factors for this variation trends are the ecological water demand and artificial cultivation.And there is positive correlation exists between them.(3)Following the recent 27 years,the dynamic change trends of four types of reeds in main Bosten Lake are as following: the overall area of first type reed is decreased in 27 years,changed from 71.05 km2 in 1990 to 66.73 km2 in 2016.Other types showed an increasing trend.It is found that the main driving factor is the water level,showing a negative correlation.(4)The dynamic change trends of four types of reeds in small Bosten Lake are as following: the area of first type of reed decreased,increased,decreased and increased again,and the overall change showed a decreasing trend,decreasing from 81.41 km2 in 1990 to 77.64 km2 in 2016.Other types of reed showed an increasing trend in the 27 years.(5)The results of non-linear relationship between areas of Pragmitesaustralis wetland and water level show that,the most suitable water level for Pragmitesaustralis in main Lake is 1046.66 m.This study also provides scientific basis for protection,utilization and ecological security of Bosten Lake.