Temporal-spatial Variation Of Wetland In The Xi'an-xianyang Section Of The Weihe River Basin

As a special ecological system of water and land on earth,wetlands and forest ecosystems and marine ecosystems are collectively referred to as the world's three major ecosystems.It not only has the function of regulating climate,storing water,storing carbon and carbon sequestration,purifying the environment,but also the habitat of many rare plants and animals,It is also known as the"kidney of the earth".However,in recent years,inadequate understanding of wetlands and the destruction of human activities have caused serious threats to wetlands.As the largest tributary of the Yellow River,the Weihe River is of great value for maintaining the healthy development of the Weihe Plain and safeguarding the ecological balance.Especially along with the development of the western region,the integration of Tianshui and Guanzhong and the construction of central cities,the conflict between urban development and wetland protection in the Xixian Section of the Weihe River Basin has become increasingly acute.Monitoring the temporal and spatial changes of the wetland in the region will have a great significance on protecting the Wetland of the Weihe River and exerting its ecological functions.It can also promote regional urban development.This paper selected four years of remote sensing imagery in 2000,2004,2010 and 2016as data sources,using object-oriented and support vector machine(SVM)and the method of Manual interaction in research area of wetland information extraction and classification,analyzing the spatio-temporal changes of the Xixian section of the Weihe River Basin and studying the changes of the wetland combined with the natural and human factors in the study area.This article has obtained the following results:1,The proportion of wetlands in the Xixian section of the Weihe River basin is relatively small.The total area of the wetland is 7857.71 hm~2 to 7930.86 hm~2,which only accounts for1.04%of the total area of the study area,Among them,river wetland area is the largest(4153.53 hm~2 to 4204.30 hm~2),accounting for 0.56%of the total wetland area,and is mainly distributed on the surface of the Weihe River and the Jinghe River.Then the artificial wetland(3562.27 hm~2 to 3602.54 hm~2),which accounted for 0.48%of the total wetland area.The distribution was relatively extensive,mainly in Xi'an Municipality and Jingyang County.The swamp wetland area(100.56 ha to 104.67 ha)accounts for 0.14 of the total wetland area,which is mainly distributed on the north of the Weihe River in Lintong District.The area of lake wetland is the smallest(39.40 ha to 40.83 ha),accounting for 0.005%of the total wetland area,mainly distributed in Seoul Lake,Weiyang Lake,etc.2,Compared the spatial and temporal distribution characteristics of wetlands in 2000,2004,2010 and 2016,the wetland in the Xixian section of the Weihe River Basin has been reduced first and then increased in the past 16 years,total area of wetlands increased by 17.60hm~2.The temporal and spatial changes of different types of wetlands are different.The area of river wetlands has decreased as a whole.In 2016,the area of rivers has decreased by 16.80hm~2 compared with 2000.The main manifestations are that the individual water surface of the Weihe River and the Jinghe River has reduced water storage,and the water surface has become narrower;the lake wetland area has been relatively stable.There is no significant change in the four years.The swamp wetland also showed a decreasing trend.From 2000 to2016,the area decreased by 4.11 ha,mainly distributed on the north side of the Weihe River in Lintong District.The area of the constructed wetland decreased slightly from 2000 to 2004,which was reduced by 1.20 ha in 2004.Since then,it has gradually increased,with an increase of 40.82 hm~2 in 2004-2016.The increase in area is mainly distributed in the districts of Jingyang County and Xi'an Municipality.3.The change of the wetland in the Xixian section of the Weihe River Basin is the result of a combination of natural and human factors.Through the analysis of the average temperature and precipitation in the study area in recent decades,the natural factors are mainly reflected in the rising temperature in the study area,the precipitation tends to be stable,and the evaporation in the study area continues to rise,resulting in a decrease in the area of wetlands.Human factors are mainly reflected in the fact that economic development and population increase have intensified the process of reducing wetlands to some extent.Policy factors are mainly reflected in various wetland protection policies in Shaanxi Province after2010.Through multivariate linear regression analysis of natural factors and human factors,the increase in construction land caused by population growth and the increase in surface evaporation caused by rising temperatures are the main driving forces for the spatio-temporal change of wetlands in the study area.