Desert Management
Year:2017 | Volume:4 | Issue:8 |Papers Count:9

Salt domes have high impact on groundwater, mineral matters and the soil quality of lowland regions due to intrusion into the saline mass and going up to surface of earth. In this process, a remarkable rate of salt going up to surface of earth and entered to lowland regions by the way of various erosional factors and effect on the soil quality. This research aims to investigate the impact of salty dome of Korsia on the soil quality of lowland regions. For this, research region is divided into four sub-regions with regarding to their land uses and distance from salt dome and 22 samples were collected from the region. Ions of Mg, N, K, Na, Ca as well as volume of pH and EC and soil texture of samples of year of 2010 was measured and while the variables of year of 1993 such as Na, Ca, SAR, EC, pH were prepared from Ministry of Agriculture. The significant differences between the various land uses and the change rates of this elements in the land uses during two periods of time were caused to identifying of effective component in the soil quality and classifying of chemical elements was determined by land uses using multivariate statistical methods such as variance analysis, independent T test, factor analysis and cluster analysis, respectively. The results indicated that all variables excepts K, Mn, pH, clay and chemical parameters such as pH and N have significant differences during period of time 1993-2010 according to their land uses; and with regarding to increasing of pH of soil in the periods of time of 1993-2010 in the agriculture land uses and existing of alkaline soils, the effect of salt dome on the soil quality of lowland is clear. The results of factor analysis introduced six components such as Ca, SAR, Na, EC, N and K as the effective variables in the controlling of soil quality of lowlands. The results of cluster analysis showed that the clustering of samples in three clusters is consistent with the land use classification.

Dust is one of the natural hazards that occur mainly in arid and semi-arid area of the world that is one of the major problems in Iran. In this paper, identification of active sources of dust generation in Alborz province using satellite images and numerical modeling to predict airflow is discussed. LANDSAT 8 satellite sensor (OLI) (from 2013 to 2015) and digital elevation models (DEMs) from the ASTER were received to produce the masks of non-erodible surface and by using vegetation, moisture, roughness indices and images classification those areas separated from the others. Also using field based dust data and HYSPLIT model (normal 5. 0 degrees), air flow path in all dust events in 2013 and 2015 was simulated and local dust event was determined. By applying the HYSPILIT matrix model, raster images of events based on the level of dust was produced for local events and specify location of the back flow of air to the ground. The masks of non-erodible surface were used on these images and WLC MCE approach was used to finalize the map of active dust sources. The results showed that the combination of remote sensing and numerical simulation methods and field based data could well show active dust sources.

Seed germination indices can be affected by drought stress in ripening stage of seeds on mother plant. In this study, four water stress treatments (100, 75, 50 and 25% of field capacity (FC)) were imposed during seed maturation of Satureja hortensis, and subsequently the effects of treatment on seed germination characteristics of S. hortensis were evaluated using a completely randomized design with four replications. The number of germinated seeds was counted each day and sampled after ten days. Then, percentage, rate of germination, vigor, mean daily germination, final germination percentage, daily germination speed, germination index and length of shoot and root were determined. The results indicated that the drought stress had a significant (P<0. 01) effect on germination rate, seed vigor as well as shoot and root length of S. hortensis. The seed germination percentage was significantly affected by drought stress at 5% level. Drought stress during maturity of seeds on mother plants had no significant effects on1000 seed weight, daily seed germination, daily germination rate and germination index. The maximum germination percentage (97. 75) was observed in 100% of field capacity and the lowest germination percentage was in the treatment of 50% FC with 87. 50. The maximum seed germination rate (10. 95) was observed in 50% of field capacity while the lowest seed germination rate (7. 94) was observed in 100% FC. The maximum seed vigor (5. 15) was obtained in 100% FC that had no significant difference with 75 FC and the lowest seed vigor (4. 07) was obtained in 50% FC that had no significant difference with 25% FC.

The lack of sufficient fresh water resources, climate change, lengthy and severe droughts are of the major today’ s world challenges particularly in arid and semi-arid regions. In the current conditions, especially in the case of droughts and in order to planning for water resources, it is essential to analyze the changes and trends in drought particularly in hyper-arid, arid and semi-arid regions of the globe. In this study, the Mann-Kendall statistics were applied to determine the significant and non-significant positive or negative trends in long term drought time series (9, 12, 18 and 24 monthly time scales) in moderate to severe and extreme classes of droughts derived based on the Standardized Precipitation Index (SPI). The results indicated that both significant positive and negative trends can be found in these regions. By increasing the time scales of drought time series, the percentage of significant upward or downward trend grow. For example, in the case of decreasing trend of SPI (increasing in the drought), the percentage of 17. 8 for 9 monthly SPI increased to 21. 9, 28. 48 and 31. 71 for the 12, 18 and 24 monthly SPIs, respectively. The increasing trend in long severe and extreme classes of drought can be found in the Middle East and west of America. The upward trends of drought particularly in the Middle East region which is suffered by expensive tensions among the communities can intensify current critical situations. Therefore, more attention should be paid to this subject particularly in the regional and international scales.

This research aims to compare the performances of the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) in terms of the monitoring and trend analysis of the climatic droughts at several synoptic stations located in the coastal areas of Persian Gulf and Oman Sea over 1992-2014. To this end, trend analysis of drought was carried out using the traditional Mann-Kendall and Trend Free Pre-Whitening (TFPW) Mann-Kendall tests. The results showed that both indices report the same behaviors, but the SPEI presents higher percentages in different drought classes and a rapid responses to humidity variations at all time scales when comparing to the SPI. Meanwhile, there were significant positive correlations between the two indices at the corresponding time scales such that the highest correlations in most of the stations with the values 0. 97 and 0. 98 were related to the time scales of 12 and 24 months, respectively. The same results were obtained for the frequency percentages of different classes of the mentioned drought indices. Trend of droughts in the region is generally increasing and the slope of trend for the SPEI is stronger than SPI as the time scale increases. Finally, the use of SPI is not sufficient to monitor droughts in arid and hyper-arid climates of coastal regions, and due to the role of temperature as the limited factor of humidity, the study recommend the use of SPEI for effective and accurate drought monitoring in such regiouse of SPEI for effective and accurate drought monitoring in such regions.

In this study, to evaluate the sediment yield of different geomorphic facies in Aran region, the wind erosion meter and IRIFR model were used. The results of wind erosion meter showed that the most speed of threshold in natural condition is belonging to hard crust and dried clay plain with a speed of 13m/s, then puffy and clay-agricultural lands with a speed of 12 m/s, and the lowest threshold speed is 6. 5 m/s related to fine-grained loamy-sandy soils of pediment that due to lack of the adhesion, flat, and smooth surface and wind shear impact and blown with wind. The results of wind erosion intensity with wind erosion meter also showed that the clay plains and puffy lands facies are most stable with sediment of 0 to 175. 2 tone/km 2 / yr which sorted in erosion class I, and sand sheet with the graveled covered, clay plain and sand dunes are the most sensitive facies, with 5450. 09 to 5517. 04 tone/km2/ yr sediment equivalent classified in erosion class IV. While the results of the IRIFR model showed that the most stable facies are agricultural lands with 415. 1 ton/km2/yr sediment erosion that classified in the erosion class II and facies sand sheet and sand dune the most sensitive facies, that with 1168. 6 ton/km2/ yr sediment equivalent classified in erosion class IV. According to statistics obtained from the two models, it is concluded that except to the puffy land and clay plain there was not significant differences among the rest of facies.

This paper aims at comparing the accuracy of regression, artificial intelligence, and adaptive neuro-fuzzy (ANFIS) interpretation methods in estimating wind speed in the Sistan region. To this end, we used the daily weather information obtained from Zabol synoptic stations during a five-year period (2010-2015). MATLAB software was used for modeling based on artificial neural network. On the other hand, DATA FIT software was used for modeling based on regression methods. The methods’ accuracies were estimated using mean square error statistics, comparison indexes, and mean error. Based on sensitivity analysis results; variables such as daily temperature mean, mean relative humidity, sunshine hours, and evaporation from pan were regarded as input variables of regression and artificial intelligence methods. Wind speed was considered as output variable. Based on the results, mean daily temperature and mean relative humidity had the most and the least effect on wind speed in Sistan (0. 42 and 0. 25 respectively). Neuro-fuzzy method with Gaussian function was the most accurate method in estimating wind speed (error squares mean of 2. 56). The same statistic for regression method is 4. 44. The correlation of regression method (0. 45 and 0. 51) is less than those of multilayer perceptron method and Neuro-fuzzy method (0. 51 and 0. 52). So, it is suggested that Neuro-fuzzy method can be used for more accurate estimating wind speed in Sistan region. With accurate estimation of this variable, we can hinder the devastative effects of wind and use it as an effective source of energy.

Wind erosion and generation of dust is one of the most important problems in the Yazd province. To control this phenomenon and overcome the damages a lot of investment has been done for the implementation of many successful and unsuccessful projects across this province. Analysis of erosive winds and estimation of the Resultant Drift Direction (RDD) of sand flow is the fundamental study by which can lead to a more successful implementation of projects, to control wind erosion. In this study, by taking advantages of Wind-rose, Storm-rose and Sand-rose has been analyzed wind speed, wind direction and calculation of wind drift potential (DP) to represent a landscape of wind erosion in the Yazd province and with the results of these analysis, the Resultant Drift Direction (RDD) of sand flow and dust be estimated. The results showed that most of the erosive winds in the Yazd province occur in the spring and summer and the lowest erosion occurs in autumn. The results as well revealed that the average percentage of erosive winds which are capable of producing dust are between 6. 4%, in Yazd city, and 23. 6%, in Herat city, and on average, in 44 days there is the possibility of dust in the Yazd province. Therefore, although the prevalence of erosive winds with speed more than 6 meter per second generally does not exceed 14% but, it has the most important role in the occurrence of the wind erosion and dust generation in the Yazd province and the mobility of a large amount of dust is generally from the southwest and west to the north east and east.

Different surface covers such as soil, rock, plant and etc, lead to be created different climate conditions in small scales by impacting on the adjacent atmospheric elements. The greatest difference tangibly in land surfaces and air temperatures were observed in arid and desert regions on hot days, which can have significant microclimate and ecological effects on environment. In this study, 8 different land surface cover including, green plant cover, dead plant cover, arable soil, cement surface, non-arable soil, pavement, asphalt and dark metal surface were measured using two types of mercury and digital thermometers to compare between the measured temperature at the Yazd meteorological station and the temperature of different land surfaces, in June and July, 2016. Then, the land surface temperatures were compared to each other and also compared with the air temperature measured at the Yazd meteorological station. Based on the results, the highest measured temperature reaches to above 70 ° C in asphalt cover and the lowest surface temperature of 47. 4 ° C were recorded in plant surface. According to the result of Kolmogorov Smirnov test, there are a significant difference between the different land surfaces and the air temperatures (R2= 0. 86) at 5% level during the measured period. Generally, asphalt and plant surfaces showed the highest (23 ° C) and the lowest (5 ° C) thermal differences with air temperature. Concluding, different land surfaces show different thermal patterns.