Human Activities And Their Effects On Soil Salinization And Degradation In The Yellow River Delta

The Yellow River delta is one of the most active estuarine deltas in China's economic development activities,which is also the last big river delta to be developed in our country.The Yellow River delta is ecologically fragile under the influence of both man-made factors and natural factors,causing that the land use structure of the Yellow River delta has changed greatly,which affects the healthy development of land resources in the area.It is of great practical significance to study the change regularity of human activities and to find the interaction model between soil salinity degradation and human activities.Based on this,this research takes the Yellow River delta as the research area,which is based on the remote sensing data,in which the statistic data is spatially and the artificial activity intensity is quantified and the land saline-alkali change of the Yellow River delta is analyzed.The influence of human activities on the land salinization is discussed in order to provide scientific reference to protect the ecological environment and to make reasonable sustainable use of regional land resources,which provide a basis for the Yellow River delta land allocation,rational use and the formulation of scientific agricultural policies.The TM and ETM+remote sensing images of the Landsat terrestrial satellites in the study area in 1980,1990,2000,2005,2010 and 2015 were the main data sources,and the preprocessing methods such as geometric rectification,band selection and clipping were made by remote sensing images,through which the research obtain information of land use remote sensing imagery.Combining with the relevant topic data and survey data,the paper uses GIS technology to interpret the LUCC of the research area,and the distribution and area of the land use types in the statistical research area.On the basis of this,the human activity Intensity index in the study period is calculated by reference to the definition of human activity on land surface.Based on the statistic data,the paper chooses 20 indexes of 3 aspects of social,economic and resource utilization,which constructs the index system of human activity intensity index by using the entropy weight method,and analyzes the spatial change characteristics of different human activity intensity in each county area in 2015 years.Based on the sampling data and the second soil census data,this paper analyzes the saline-alkali degeneration in the Yellow River delta area in the past 40 years,which analyzes the degree,area,distribution and dynamics of soil salinization,and provides scientific basis for the improvement and efficient utilization of saline soil resources.The study draws the following conclusions:(1)According to the transfer matrix of land use type in the study area,the change of land use type in the study area was very strong from 1980 to 2015.The overall area was increased from the 1980's 16305.24km~2 to the 16609.34km~2 mainly because the Yellow River carries sediment and land in the estuary.During the study,the proportion of cultivated land in the Yellow River delta area is the largest,and the forest land is the smallest,and the cultivated land,forest land and construction land is increasing,among which the biggest change rate is the construction land,which is 8.66%,from 1370.61 km~2 to 2834.91 km~2,while the trend of grassland,water area and unused land is reducing.The largest variation is the unused land,of which the annual rate is-7.56%,and reduce from 2205.17 km~2 to 991.65 km~2.Land use changes in order:construction land,unused land,grassland,cultivated land,water area,forestland.The utilization rate of land in the Yellow River delta region increases by years from1980's 86.48%to 2015's 94.03%and the landscape deviation increase from 69.56%to80.99%,which reflect the extent of the transformation of natural environment in the Yellow River delta area,and the transformation process of human activities to nature is gradually enhanced.(2)The calculation model of human activity intensity put by Xu Yong,is used to calculate the intensity of human activity near 40?in the Yellow River delta area,which use the percentage of construction land in total area land.Over the past 1980-2015 years,the equivalent area of construction land has continued to grow and human activities have continued to increase.The equivalent area of construction land was 4382.91km~2 in 1980 with the intensity of human activity of 26.88%and the equivalent area of construction land was5825.50km~2 in 2015 with the intensity of human activity of 35.07%.The average annual growth of construction land equivalent area is 41.22km~2,and the average annual growth rate of human activity is 0.23%.(3)Using the Entropy method,from the social,economic,resource utilization three aspects of the system analysis,combined with the availability of data,this paper finally choose 20 indicators to complete the Yellow River delta region human activity intensity Analysis Index construction.The social factor level mainly considers the population number of the research area,the level of population education,urbanization and so on.Economic factor level mainly consider per capita GDP,per capita disposable income,three production proportion,the whole society fixed assets investment,etc.The utilization of resources mainly considers the land reclamation rate,the amount of fertilizer application,the total power of agricultural machinery and so on.(4)From 2015 to 2016,855 effective samples were collected in the Yellow River delta area for laboratory analysis.In ARCGIS10.1 software,the spatial distribution map of soil salinization in the study area was IDW,and the soil salinization dynamic change of the research area was ascertained by the superposition analysis with the second soil census data.During the study period,the total soil salinization decreased by 17.83%,in which mild salinization increased by 59.54%,moderate salinization decreased by 26.38%,severe salinization decreased by 26.20%,and salt soil decreased by 99.74%.The area of salinity reduction is widely distributed throughout the study area,and the degree of salinity reduction is higher to a certain extent,which shows the effect of soil improvement and utilization and the construction of"the Bohai Granary".But at the same time,the area proportion of salinization increase is also relatively high,reflecting the complex change of soil salinization in Yellow River delta area.(5)As far as the Yellow River delta is concerned,the intensity of human activity increases continuously during 1980 to 2015 years,the proportion of salinization decrease is much higher than that of salinization,and the overall level of salinization is reduced,which shows that reasonable human activities play a positive role in the degradation of soil salinity.In the case of Dongying and Binzhou,the intensity of human activity in Dongying is slightly weak and the intensity of human activity in the near 40?increased by 6.84%from27.64%to 34.37%with the annual rate of change of 0.20%and Binzhou increased by 9.38%from 26.22%to 35.60%with the annual change rate of 0.27%.In the same period,the salinity area of dongying increased by 15.18%and the salinization area of Binzhou decreased by43.13%.The area of salinization increased only 2.72%.From this,we can see that human activities have two sides to the degradation of soil salinity.To Dongying,which is located at the estuary of the Yellow River,the unreasonable human activities have negative effects,and the improvement of coastal saline soil still needs continuous attention.Specifically to the county level,the intensity of human activity in the Kenli area and Wudi County is similar where the salinization level index varies widely.Mainly by the Kenli County natural conditions,with the increase of human activity intensity,there is a negative effect on soil salinization degradation.From this,we can see that the influence of human activities on the degradation of soil salinity is restricted by the natural environment,which varies from area to region.It is of great practical significance to study the change law of human activities and to find the interaction model between soil salinity degradation and human activities.