| Desertification is an ecological environmental problem of great concern at home and abroad,and is one of the natural disasters that bring crisis to the survival of human beings.Hunshandak Sandy Land is located in the middle of the desertification area in northern China and is one of the most serious desertified areas in China.It is also a typical grassland desertification area.The desertification situation in this sandy land not only affects local development,but also has a great impact on the ecological environment and economic development of Beijing and Tianjin and Hebei,including the capital.Therefore,The application of remote sensing technology in the monitoring of resources and environment,the accurate study on the process of desertification change and its main causes in time and space,in order to promote the control of desertification and restore the local ecology in Hunshandak Sandy Land.It is of great value to protect the sustainable development of ecological fragile areas and restore the function of ecological barrier in the capital.Taking Hunshandak Sandy Land as the study area,using eight Landsat remote sensing image data from 1986,1990,1995,2000,2004,2007,2011 and 2016,after pre-processing the data,the desertification index was constructed by using normalized vegetation index as the parameter index.The spatial and temporal distribution and change of desertification index in Hunshandak sandy land in recent 30 years are analyzed.The spatial and temporal trend of sandy desertification index is analyzed by using Theil-Sen trend analysis method and Mann-Kendall significance test method,and the time of sandy land in recent 30 years is discussed.The spatial distribution data of mean air temperature and rainfall in sandy land over the years of 1986-2016 are obtained by linear regression Kriging interpolation method,taking the annual mean air temperature and annual rainfall from 1986 to 2016 as the main indexes of climate influence factors.The Spearman rank correlation method was used to analyze the driving effect of climate factors on the rule of desertification evolution on time-space scale.The socio-economic statistics of Hunshandak Sandy Land from 1986 to 2016 were taken as the index of human factors.To explore the driving effect of human activities on the evolution of desertification in Hunshandak Sandy Land.The following main conclusions have been reached:(1)In terms of spatial distribution,the degree of desertification in Hunshandak Sandy Land decreased from west to east,the desertification index of Sunite right Banner in the westernmost part of the sandy land was 0.89,and the degree of desertification was the heaviest.The desertification index of Weichang Manchu and Mongolian Autonomous County in the eastern part of sandy land is 0.28 and the degree of desertification is the least.(2)The evolution of desertification in Hunshandak Sandland has gone through five periods.From 1986 to 1990,the area of severe desertification and extremely severe desertification decreased by 964.02km2,1540.3176km2,and sandy land is in recovery period.From 1990 to 2000,desertification began to expand from west to east,severe desertification and extreme desertification increased by 5016.33km2,3045.88km2,sandy land was in the period of desertification development;2000-2004 not desertification,light desertification increased 1223.82km2,5241.12km2,desertification path from 2004 to 2007,the increasing area of severe desertification and extreme desertification reached 26.13%and 36.29%of the total area,and desertification was in a period of rapid development.From 2007 to 2016,severe desertification and extremely severe desertification reduced 3758.03km 2,8098.96km 2,and sandy land was in the reverse phase of desertification.(3)The trend of desertification change in Hunshandake Sandy land is mainly non-significant trend,and its area reaches 0.73 of the whole area of sandy land,and the rising trend type accounts for 0.2 of the sandy area in the significant change trend of significant level P<0.05,of which the junction of Abaga Banner and Sunite Left Banner of the north-central border is the most obvious area of the upward trend.The decline trend type accounts for 0.07 of the sandy area,mainly distributed in Sunite right Banner.(4)From the point of view of time,human activity is the most important reason to promote desert evolution in the process of desertification evolution in Hunshandak Sandland in recent 30 years,in which the number of livestock is the most important human activity factor;The correlation between climate change and desertification evolution is relatively weak,which is the secondary cause of promoting desertification,and the driving effect of rainfall on desertification is stronger than that of temperature.(5)In terms of spatial distribution,according to the grade of meteorological influence on desertification and the relative influence of meteorological action and human activities on the process of desertification in Hunshandake sandy land,the sandy land is divided into the first,second and third influencing areas of meteorological factors.It is found that in the past 30 years,19.14%of the Hunshandake sandy land is the first influencing area of meteorological driving effect,and meteorological and human activities are the first influencing area of meteorological driving effect.The driving contribution rate of desertification is difficult to measure,and the influence of meteorology is stronger than that of other regions,mainly distributed in the area adjacent to Sunite Left Banner and Abaga Banner in the northern part of the sandy land;73.85%of the area is the secondary influencing area of meteorological driving role,the influence of meteorology on desertification is weak,and human activities are the main driving factor of desertification,and the spatial distribution is uniform in 7.01%of the area.In the affected area,the meteorological factors are the weakest.The influence of human activities on desertification covers the meteorological effects and is the main driving factor of desertification,mainly distributed in the Sunite Right Banner in the west of the sandy land. |
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