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.
Mohhamad Fayaz; Saeedeh Nateghi; Hassan Yeganeh; Taghi Mirhaji; Seyed Ahmad Mousavi
Abstract
In this study the effect of month, place and different years on the preferencevalue of Bromus tomentellus in semi-steppe region was studied. The preferencevalue of the Bromus tomentellus was studied in two years and four months in three sites as cheshme anjir (Fars), Badamstan (Zanjan) Firuzkuh (Tehran). ...
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In this study the effect of month, place and different years on the preferencevalue of Bromus tomentellus in semi-steppe region was studied. The preferencevalue of the Bromus tomentellus was studied in two years and four months in three sites as cheshme anjir (Fars), Badamstan (Zanjan) Firuzkuh (Tehran). To determine the preferencevalue of species the two methods of as preference index and timing method was used. To compare preferencevalue in different sites times the factorial completely randomized design was used. Mean comparison was performed using Duncan's Multiple Range Test at 5% level. And to compare two methods whit each other the T test was used. The results of preference index showed that sites were significant at 1% level. But the other factors were insignificant differences according to the results of timing method all the factors were insignificant. Comparison of two methods by T test showed that the two methods were different.
