جستجوی مقالات مرتبط با کلیدواژه « Sand dunes » در نشریات گروه « آب و خاک »

Wind erosion is one of the most important natural processes in arid and semi-arid regions. Sistan plain has a hyper-arid climate and is one of the windy regions of the country. Due to the soil characteristics of the Sistan plain, wind erosion is very intense in this region. In this study, the relationships between some soil's physical and chemical properties and wind erosion were investigated in different land cover in a part of the central region of Sistan in 2018. A map of land cover in five classes was prepared using the results of field studies and the classification of satellite images. Fifty soil samples at a depth of 10 cm were collected to investigate the physical and chemical soil properties and the wind erosion threshold was determined at each location using a portable wind tunnel device. Also, the relationship between physical and chemical soil properties including soil texture, soil moisture, specific apparent weight, EC, SAR, ESP, Na+, k+, with the speed of wind erosion threshold was investigated. According to the results, the highest and the lowest threshold speed were 8.2 and 3.8 m s-1 and occurred in agricultural lands and hilly lands, respectively. The results of this study indicated that the velocity of wind erosion threshold in different lands adjacent to sandy areas is less than the average of that cover. Also, the soil texture, EC, and SAR have the most significant effect on soil wind erodibility at P <0.05 in the study area.

This study was done to evaluate the effect of afforestation in sand dunes at the vicinity of Shush, because of the importance of soil protection and wind erosion in sand dunes, also sand dunes afforestation as an effective and long lasting fixation mechanism. The study site was covered by petroleum mulch about 20 years ago and afforested by Prosopis juliflora. To study the effects of afforestation on sand dunes, two 10 ha afforested sites (25-50 and 75-100 percent canopy coverage) and control were selected. In each of studied site 15 plots were established and soil physiochemical properties were determined. Our result indicated that afforestation caused soil texture to change from sandy to sandy-loam. Also, soil phosphorus, potassium, organic carbon and nitrogen increased in 0-5 cm soil depth by afforestation that could be because of nutrient absorption from soil depth and returning to the surface by litter fall compared to the control. This study revealed that 25-50 percent canopy coverage resulted in better soil physiochemical properties compared to control site. In conclusion, sand dunes afforestation not only resulted in sand dunes fixation but also soil fertility and long lasting fixation.

Soil is known as a suitable reservoir for carbon sequestration. The objective of this study was to investigate the capability of haloxylon on sequestration of carbon in sand dunes of Yahya Abad, Sabzevar, in northeastern Iran. Eighty soil samples were taken from two depths of 0-5 and 5-10 cm under and between haloxylon trees. Eight soil profiles under and between haloxylon trees were described and sampled to explore subsurface variations of soil organic carbon (SOC). The results showed that SOC in 0-5 cm has increased from 0.18% in between trees to 0.79% under trees and similarly, in 5-10 cm has increased from 0.11 to 0.29%. SOC has decreased exponentially with increasing depth. A strong correlation was found between soil organic carbon and electrical conductivity in 0-10 cm depth due to accumulation of salts in haloxylon litters that has increased both SOC and electrical conductivity of surface soil. The SOC storage under and between haloxylon trees at 0-100 cm depth were estimated 27718 kg ha-1 and 14915 kg ha 1 respectively, that diferenemnce of these values represents carbon sequestration. The amount of carbon sequestration to depth of 10 and 40 cm was 5367 and 10155 kg ha-1 that is 36 and 68% of total carbon sequestration. The results of this study confirmed the importance of haloxylon in carbon sequestration in desert environments.

This study aimed to evaluate the potential of image ratioing techniques to detect and map the extent and particle composition of sand dunes in the Erg of Gavkhouni in Isfahan province. The 6/4 ratio index and also a new index called SaDI which was calculated using Landsat band 3، 6 and 7 were applied to a georeferenced Landsat TM image. To evaluate the performance of ratio techniques، the extracted images were correlated with the percentage of different particles collected in 33 sampling sites. Results showed that both ratioing techniques were able to detect and map the spatial distribution of sand dunes and there was more than 70% agreement between image indices and field data. The results also indicated that the performance of SaDI was 50% better in mapping carbonate particles and this confirms that this index is more appropriate than 6/4 index for mapping sand dunes dominated by carbonate particles.