| It is of great significance to understand the causes of soil and water loss in the Nandong basin,then put forward the countermeasures to control water and soil erosion so as to improve the ecological environment in the area and improve the living quality of people.The paper draws conclusions through rain collection research and experimental studies on soil sampling and data collection,and by researching the rainfall factor, soil factor, terrain landform factor, land use factor and human factor of Nandong typical depression -Zhumashao depression soil and water loss and basing on Soil and Water Conservation, Soil Analysis Method and Geoinformatics and using classical statistical analysis, correlation analysis and semi variance function, soil wet sieving method and dry sieving.(1) Zhumashao depression's rainy seasons are July,August and October and it has abundant rainfall and large rainfall intensity.Zhu's dry seasons are January, February and March and it has small amount of rain and low rainfall intensity.The obvious dry and wet months has strengthened the rain's erosion intensity on the soil. Using rainfall 9.2mm as standard of erosive rainfall,there arel4 erosive rains in data cycle which are 17.7% in the number of rains and 65.1% of total rainfall.From 2015.7.16 to Marchl 5,2016, the rainfall erosivity is 1514.62MJ.mm/ (hm2*h) in Zhu depression.(2) Zhumashao depression soil bulk density, moisture and organic matter exist spatial heterogeneity; soil organic matter content is 5.553kg/m3,and the content is lower than the karst ecological standard value which is showed that the soil has degraded to a certain extent. According to Pearson correlation analysis between the soil bulk density, soil moisture and soil organic matter,it can be found that the negative correlation exists between soil bulk density and water, soil bulk density and organic matter. And the correlation coefficient are respectively-0.609 and-0.581.(3) According to the semi-variance analysis,0-20cm soil moisture, bulk density, organic matter and the spherical model fitting is better and the fitting degree of R2 were 0.911,0.977, 0.922; 20-40cm, moisture, bulk density, organic matter and Gauss model fitting is better and the fitting degree of R2 were 0.647,0.730,0.881. The nugget coefficient showed that the factors of 0-20cm and 20-40cm have weak spatial correlation and it may be related to human activities in space.(4) The distribution of soil bulk density become bigger as the depth increase but the water and the organic become smaller as the depth increase. In the center of the depression, bulk density has the maximum while it becomes smaller as the depth increase on the both sides of the slope. In the distribution of the surface water, the southeastern slope is greater than that of the northwest slope. In the mesoslope and the gully slope area has relative Wa's value. And the distribution of deep horizontal is decreasing from southeast slope to the northwest slope. In the distribution of organic matter levels, the soil bulk density shows that both sides are high but the middle is low. The organic matter content of southeast Slope is bigger than that of the northwest and the organic matter of the lowland central is the lowest.(5) Zhumashao depression is located in the downstream of Karst Hilly depression in Nandong basin, which is the second part of the Middle Triassic Gejiu group(T2g2).Its permeability is strong, which belongs to the water bearing stratum, and it has the typical characteristics of karst water and soil erosion. By using the classic LS numerical calculate, the LS numerical of the two slope of Zhumashao were 10.516 and 12.584 respectively.(6) According to the analysis of the usage of different layers of soil, we can get the result about the rank between cultivated land,grassland and shrub. About the amount of water, cultivated land is in the first place, grassland is the second and shrub ranking the third. On volume weight, shrub rank first, following by grassland then the cultivated land.As the organic content, cultivated land is in the first place, grassland is the second and shrub ranking the third. According to the distribution of soil mechanical composition, the rank should be cultivated land the first and grassland the second and shrub the last. The way that people plow in Zhu Ma Shao depression influence its capable to remain the water and soil. The increase of volume weight and the decrease of water and organic content will make the soil more viscous and easer to be eroded.(7) Dry sieving method, the large aggregate that is greater than 5mm, shrubs (61.82%)> cultivated land (50.94%)> grassland (45.83%), of the large aggregate content of dry sieving size that is greater than 5mm determines the height of the average size of MWD.Wet sieving method, the large aggregates that is greater than 5mm particle size shows that shrub (48.45%)> cultivated land(17.63%)> grassland (13.28%); the large aggregates that is greater than 0.25mm particle size shows that shrub (84.56%)> cultivated land(72.57%)> grassland (68.69%). Wet sieving method>5mm of> 0.25 mm, the particle size aggregate content that is greater than 5mm and 0.25mm in the wet sieving method determines the height of the average size of MWD.The PAD value and MWD value of aggregate destruction rate showed different trends, and the size of PAD was arranged as farmland (15.29%)> grassland (8.05%)> grassland (6.12%).by doing the correlation between the content of soil aggregates and organic matter of regression analysis there is the regression equation y=3.8957x+56.88,and correlation coefficient R2 was 0.5767, which indicated that the soil aggregates content and organic matter content showed a positive correlation. |
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