| The Agriculture and animal husbandry interlaced zone in Ordos Plateau is located in the middle of the ecotone of northern China,and the ecological environment is fragile.Because of the comprehensive influence of natural and human factors,the soil erosion and desertification are seriously damaged.The study of soil surface grain size in the Agriculture and animal husbandry interlaced zone is of scientific significance to the evaluation of soil quality and desertification degree.Through the soil surface samples in the study area analysis,we discussed the grain size characteristics of different types of sediments and different land use patterns.The results showed that:(1)The surface sediments are Sand loess,Sand covered loess residues and Weathering residues,and the contents of silt is 37.28% ~ 52.83%,very fine sand is 16.81% ~ 35.21%,fine sand is 8.41% ~ 21.74%.Among them,surface sediments are Weathering residues,and the surface soil has more medium sand and coarse sand content.The surface soil grain components of Aeolian sand was mainly fine sand(53.85%)and middle sand(26.13%).(2)Among the soil grain size parameters of the four surface sediments,the average grain size of Sand loess(4.78?)and Sand covered loess residues(4.62?)soil belong to silt grade,Weathering residues(3.80?)and Aeolian sand(2.46?)soil belong to fine sand grade.Sorting is best with aeolian sand(1.37),and weathered residue(2.41)is the worst.The skewness is characterized by weathering residue(0.19)and sand-covered loess residue(0.19),which are positively biased.Sandy loess(0.35)and aeolian sand(0.44)are extremely positively biased.The kurtosis value shows that the grain size distribution of Aeolian sand(2.30)is the most concentrated.(3)Different land use types of the same surface sediments have obvious differences in surface soil fractions.The same surface sediment,there were more coarse grains(0.56%~9.82%)such as gravel and very coarse sand in farmland,more silt(38.65%~60.33%)in grassland,and more very fine sand(22.46%~39.93%)in forest land.Fixed dunes have the more silt content(12.76%)and semi-fixed dunes have the most fine sand content(57.73%),gravel and very coarse sand are only distributed in mobile dunes(3.12%).(4)The fractal dimension of soil grain is as follows: Sand loess(2.5242)> Sand covered loess residues(2.4373)> Weathering residues(2.3554)> Aeolian sand(2.2815).The fractal dimension of soil grain in Sand loess and Sand covered loess residues was significantly positively correlated with silt;the soil fractal dimension of Weathering residues is negatively correlated with gravel;the fractal dimension of Aeolian sand soil has significant negative correlation with fine sand and middle sand.The correlation between fractal dimension of surface soil and grain content was significant different from that of surface sediment.The fractal dimension of soil particles can be used as a comprehensive index to characterize the characteristics of soil grain size.(5)In the same sediment,the content of easy-to-erosive particles and the degree of wind erosion were significantly different from each other.The Sand loess showed forest land(85.13%)> farmland(79.21%)> grassland(77.43%).The residue of Weathering residues is forest land(84.06%)> farmland(69.82%)> grassland(65.87%).The wind erosion of farmland and grassland is strong,and that of woodland is the strongest.The weathering residues were forest land(58.07%)> farmland(54.83%)> grassland(52.43%).The sand dunes tend to appear as mobile dunes(92.42%)> semi-fixed dunes(91.31%)> fixed dunes(88.10%). |
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