saeedeh Nateghi; Rostam Khalifehzadeh; Mahshid Souri; Morteza Khodagholi
Abstract
Soil organic carbon is one of the most important indicators of soil quality. The purpose of this study is to study the spectral and non-spectral behaviors of soil in order to estimate the organic carbon of topsoil using factor analysis and multiple regression methods in the semi-steppe rangelands of ...
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Soil organic carbon is one of the most important indicators of soil quality. The purpose of this study is to study the spectral and non-spectral behaviors of soil in order to estimate the organic carbon of topsoil using factor analysis and multiple regression methods in the semi-steppe rangelands of Asuran, Semnan province. Soil sampling was performed using stratified random sampling method. After creating a map of homogeneous units in the area, in each homogeneous unit according to its area, several sampling points were selected completely randomly. A total of 145 sampling points were collected. At each sampling point, a composite soil sample (a mixture of 9 observations) was taken. Soil organic carbon was measured using Valkyli-Block titration method. Data of 114 samples were used to calibrate the model and data of 31 samples were used to validate it. The results showed that the correlation of spectral variables obtained from Landsat OLI sensor with surface soil organic carbon is higher than non-spectral variables obtained from 1: 25000 topographic maps. Also, the results of factor analysis by principal component analysis with eigenvalues greater than one showed that the total cumulative variance explained by 14 variables was equal to 90.2%, which was explained by three factors. The regression equation generated by the three extracted factors had suitable potential for predicting surface soil organic carbon (R2 = 0.59). The root mean square error (RMSE) of the proposed model was calculated to be 0.3.
Mohsen Padyab; Sadat Feiznia; Hassan Ahmadi; Ardeshir Shafei
Abstract
Small precipitation with temporal and spatial variation of rainfall is the main responsible factors on flood occurrence in arid and semi arid regions. Floods in their regions usually contain high concentration of sediments which when they are deposited on the surface of lands, they change the properties ...
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Small precipitation with temporal and spatial variation of rainfall is the main responsible factors on flood occurrence in arid and semi arid regions. Floods in their regions usually contain high concentration of sediments which when they are deposited on the surface of lands, they change the properties of soils of the area. In this research, the effect of floodwater spreading on physic-chemical characteristics of soil in Gachsaran floodwater spreading station, after 12 years of floodwater spreading, is investigated. For this purpose, soils and sediments were sampled from 0-15, 15-30, 30-45 and 45-60 centimeter depths, from the flood spreading and representative (without floodwater spreading) fields. Samples were analyzed for following proportion: percentages of clay, silt, sand and gravel, pH, EC, percentage of lime, anions and cations. The result have show that the amounts of clay, silt and sand have increased, chemical properties have changed slightly and among the chemical properties, pH and percentage of lime have higher change so that pH decreased and lime increased in floodwater spreading field respect to the representative field. It is concluded that due to floodwater spreading, physical properties of the field underwent considerable amount of changes and gravelly texture has changed to less gravelly texture. The surface soil has undergone more changes and from the surface to the depth, change of physical and chemical properties becomes negligible.
