Land Use/Cover Change Impact On Wetland Landscape Pattern In The Middle Reaches Of Heihe River In The Past Forty Years

Wetland is one of the most eco-diverse ecological landscape in nature,which plays an important role in conserving water,regulating climate and maintaining biodiversity.Due to the influence of natural factors and human activities,the wetland area in the middle reaches of the Heihe River dropped,the degree of fragmentation increased,the biodiversity was low,and the wetland ecosystem degraded.Therefore,it is of great practical significance to study the influence of land use/cover change on wetland landscape in the middle reaches of the Heihe River,which protect the limited ecological environment resources,maintain biodiversity and regional ecological security in Heihe River Basin.In this paper,remote sensing images were used as the main data sources to obtain the land use/cover pattern of the middle reaches of the Heihe River from 1975 to 2016.The dynamic process of land use/cover change in the middle reaches of the Heihe River in the past 40 years was analyzed by the transfer matrix and land use dynamics,at the same time,the wetland landscape in the middle reaches of the Heihe River was calculated by calculating the wetland landscape index.On this basis,by the land use/cover change process impact on the wetland area,the impact of land use intensity change on wetland landscape,the relation between land use type and the wetland,from the three aspect,in order to state the influence of land use/cover change on wetland landscape in the middle reaches of the Heihe River.The main conclusions are as follows:(1)Between 1975 and 2016,the land use /cover pattern changed significantly in the middle reaches of the Heihe River.Among them,the cultivated land,urban and rural areas are increased,While the woodland,grassland,wetlands have a relatively reduced trend.The land use dynamic degree is basically increasing in the different period of the study area,and the dynamic degree of urban and rural residents is5.39%.(2)During the period from 1975 to 2016,the wetland area in the middle reaches of the Heihe River showed a decreasing state,and the degree of fragmentation was significantly increased.The plaque density of various types of wetland in the middle reaches of Heihe River showed an upward trend,the average area of plaques and the maximum plaque index show a decreasing trend as a whole.Wetland landscape uniformity and diversity generally increased first and then decreased,and the average adjacent index showed a decreasing trend.(3)From 1975 to 2016,the conversion from land use type and wetland type was mainly concentrated in grassland-canal-cropland,grassland-shoaly land-farmland,meadow-reservoir pond,reservoir pond-unused land-shoaly land,unused land-marsh.The wetland change rate was significant in the five periods of the study area.The change of land use intensity was also significant in human activities.The correlation coefficient between the two is 0.9998,and the change of land use intensity directly affects the change of wetland landscape.According to the results of the correlation between land use type and wetland type,the correlation degree between wetland type and land use type is higher.The correlation between cultivated land and wetland type was the highest,followed by grassland,urban and rural residents mining land and unused land,and forest land had little impact on wetland type and lowest correlation.