Abbasali Sanadgol
Volume 10, Issue 3 , September 2019, , Pages 321-338
Abolghasem Dadrasi Sabzevar; Alimohammad Akhondali; Fereydon Radmanesh; Aliakbar Norouzi
Volume 24, Issue 2 , July 2017, , Pages 370-382
Abstract
The purpose of this paper was to make the preparation of soil surface moisture map applied in arid and semi-arid regions using satellite imagery of OLI and TIRS along with the calculated values for spectral reflectance, principal component analysis and Tasseled Cap transformation.Twenty-four predictor ...
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The purpose of this paper was to make the preparation of soil surface moisture map applied in arid and semi-arid regions using satellite imagery of OLI and TIRS along with the calculated values for spectral reflectance, principal component analysis and Tasseled Cap transformation.Twenty-four predictor variables were used and the most correlated ones were identified at three moisture levels of 4 to 5 percent, more than 5 percent and less than 4 percent by exploratory regression and bivariate correlation method through calculating the inflation factor of variance, Pearson coefficient and coefficient of explanation. The Moran'sI index was used for geo-spatial autocorrelation. Forty-seven soil samples were collected randomly by creating 1800-meter networks in a systematic algorithm and the soil moisture was calculated by W-thermal method. The estimation functions of soil surface moisture were derived in the form of partial least square regression (PLSR), enter regression and stepwise regression. All models had acceptable calibration. Our results clearly showed that the Landsat 8 data could be useful in estimating soil surface moisture and the accuracy of the functions extracted with stepwise regression method was more than that of other methods (RMSE=0.585 to 1.425 %). The models introduced for a moisture level of ≤5%, tend to over estimate (MBE= 0.788) and for other moisture levels tend to underestimate.
Ali Ehsani; Hosein Arzani; Mahdi Farahpur; Hassan Ahmadi; Mohammad Jafari; Mortezah Akbarzadeh
Volume 19, Issue 1 , June 2012, , Pages 1-16
Abstract
In this study, potential and actual evapotranspiration were estimated by Penman- Matis using climatic data of Saveh Station, and plant and soil characteristics were estimated by Cropwat 8.0 software. Our results showed that potential evapotranspiration in growing season was 6.16 times greater than the ...
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In this study, potential and actual evapotranspiration were estimated by Penman- Matis using climatic data of Saveh Station, and plant and soil characteristics were estimated by Cropwat 8.0 software. Our results showed that potential evapotranspiration in growing season was 6.16 times greater than the average of actual evapotranspiration. Actual evapotranspiration was 1.18 times greater than the average precipitation of growing season. It means that plant species have used the stored moisture for actual evapotranspiration. According to the estimation of actual evapotranspiration in a ten-year period, a model was provided for forage production as Ya= 74.30+ 2.698 (ETact). Accordingly, average forage production of the studied site was estimated as 257 kg/hec. It could be said that actual evapotranspiration as an index for climate yield is one of the fundamental factors in improving water use efficiency. Application of the mentioned climate index in different estimation models of long term forage production could be considered in order to determine the rangeland grazing capacity and developing rangeland insurance as a replacement for the usual methods of production.
Hamid reza Mehrabi; Mohammad reza Chaichi; Reza Tavakolafshari; Hasan Madah Arefi; Ghavamodin Zahedi Amiri
Volume 17, Issue 3 , October 2010, , Pages 489-498
Abstract
Applying methods like seed coating which result in germination improvement, reduction of environmental stresses and increase of range species establishment is utmost important. This experiment was performed to evaluate the effect of different seed coating methods on Sanguisorba minor seed germination ...
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Applying methods like seed coating which result in germination improvement, reduction of environmental stresses and increase of range species establishment is utmost important. This experiment was performed to evaluate the effect of different seed coating methods on Sanguisorba minor seed germination under drought stress and different sowing depths. A factorial experiment in a completely randomized design with three replications was conducted in this research. Treatments included three soil moisture levels (9, 14 and 21 percent of soil dry weight), two sowing depths (surface and three times the diameter of seed), and four seed coatings (control or no seed coating, organic matter, hydro gel and clay seed coatings). Germination percentage was recorded during the experiment. The results of main treatments showed that regardless of the coating type, the effect of all three coating materials on seed germination percentage was significant (p<0.01). The triple interaction effects of soil moisture, sowing depths and coating materials indicated that in surface sowing and all soil moisture levels, there was a significant difference (p<0.01) in seed germination percentage between seed coating and control treatments. No germination was observed in control treatment with 9% soil moisture and surface sowing. Germination percentage for control treatment with 14% soil moisture was 20% recorded as the second rank among the lowest germination levels. In treatment of three times the diameter of seed as sowing depth with 21% soil moisture, there was no significant difference in germination percentage between control and seed coating treatments.
Reza Bagheri; Mohammad reza Chaichi; Mohsen Mohseni Saravi
Volume 17, Issue 2 , September 2010, , Pages 301-316
Abstract
This research was studied in order to determining grazing intensity effects on soil moisture and vegetation in Khabr region of Kerman province for two years. Natural sites under three grazing pressures (heavy, moderate and non grazed) with same ecological factors were selected from Khabr National Park ...
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This research was studied in order to determining grazing intensity effects on soil moisture and vegetation in Khabr region of Kerman province for two years. Natural sites under three grazing pressures (heavy, moderate and non grazed) with same ecological factors were selected from Khabr National Park and near rangelands. After determining sampling area, soil moisture factor was investigated monthly (on grazing period) in 0-15 and 15-30 centimeters depth of each site with 5 replication and canopy cover sampling was conducted in three temporal stages (before, middle and after grazing) using line transect method in three replication for each site. SPSS package was used for statistical analysis. Result showed that heavy grazing reduced total canopy cover, specialy perennial grass and shrubs, than non grazed site in the end of grazing period. Also heavy grazing reduced the soil moisture content with decreasing rate as 16.87% and 25.07% , than moderate and non grazed sites , respectively. Harmful effect of drought in 2006 was severly affected on heavy than moderate and non grazed site. According to results, non and moderate grazed sites occure in state condition (due to more canopy cover of Artemisia sieberi and other species such as prennial grass) and heavy grazed site occure in transition to downward state condition (due to one dimentional dominant of Artemisia sieberi and emergence of undesirable species such as Marrobium vulgaris and Peganum harmala) in state and transition model of Iranian Artemisia habitat. Thus, without management plan, we will observe dominance of undesirable species and rangelands degradation.