Study On The Influence Mechanism Of Different Vegetation Coverage Condition On Earth's Critical Zone Parameters

With the development of economy and society,the construction of ecological civilization becomes more and more important.The concept that mountains,rivers,forests,farmland,lakes and grass are a community of life has been deeply rooted in people's hearts.Eastern Hebei is the largest iron ore production base in China,and also an important grain producing area in North China.While promoting the rapid development of local economy,it also causes a series of ecological environmental problems.It is of great practical and scientific significance to carry out the research on the influence mechanism of different vegetation coverage conditions on the parameters of the Earth's Critical Zone in eastern Hebei Province for regional food security and mine ecological restoration.Taking eastern Hebei as an example,the spatial distribution characteristics and genetic mechanism of chemical ions in groundwater,the change characteristics of soil physical and chemical properties with soil depth,and the spatial distribution characteristics of heavy metal content in maize grains under different vegetation cover conditions were analyzed,and also the main controlling factors of spatial distribution of heavy metals in maize grains in the study area were discussed by using random forest algorithm.The main understandings and conclusions are as follows:(1)The difference of vegetation cover index between east and west banks of the study areaThe vegetation coverage index of the eastern bank of the study area varied from 0.36 to0.51,and the vegetation coverage index of the western bank varied from 0.40 to0.51.Comparatively speaking,the vegetation coverage of the west coast is better than that of the east coast.(2)Differences in the spatial distribution characteristics and genetic mechanism of groundwater chemical ions under different vegetation coverage conditionsThe average mass concentration of cation and cation,p H value and TDS content of groundwater in the east bank of the study area are all higher than those in the west bank.The hydrochemical type of groundwater in the east bank of the study area is mainly HCO₃-Ca type,and the hydrochemical type of groundwater in the west bank is mainly SO₄-Ca type.(3)The difference of soil physical and chemical properties with soil depth under different vegetation coverage conditionsThe average percentage content of major minerals,average soil water content and median soil particle size in the east bank of the study area were higher than those in the west bank.The soil microbial biomass carbon and nitrogen content in most soil boreholes in the west coast was higher than that in the east coast.The vertical distribution showed that the contents of heavy metals and available metals in most boreholes on the east and west banks of the study area were easy to be enriched in the surface layer,and the contents of heavy metals and available metals gradually decreased with the increase of soil depth.(4)Spatial distribution characteristics of heavy metal content in maize grains under different vegetation coverageThe contents of Cd,Fe and Zn in corn grains in the east bank of the study area were higher than those in the west bank,while the contents of Cu and Mn in corn grains in the west bank of the study area were higher than those in the east bank.(5)Based on the analysis results of random forest algorithm,the main controlling factors of the spatial distribution of heavy metals in corn grains in the study area were identifiedAccording to the analysis results of random forest algorithm,the main controlling factors of spatial distribution of different heavy metal elements in corn grains from the east and west sides of the study area are different.The main controlling factors of spatial distribution of the same heavy metal elements are also different.