Desert Management
Year:2018 | Volume:5 | Issue:10 |Papers Count:9

In the present study the most effective climatological parameters for prediction of evapotranspiration using feature selection algorithm in Darab city located in southwest of Fars province was selected. In the first stage, the values of evapotranspiration were calculated based on FAO Penman-Montith method, then using feature selection method, the most effective parameters were selected among all effective parameters to evapotranspiration prediction based on FAO Penman-Montith method. Using Best First, Greedy Stepwise and Ranker as the most famous methods of feature selection the most effective parameters from 120 data were selected. Also in order to investigate of the error of each method to choose the best method Naï ve Bayes, J48 and LMT was used. Using minimum, maximum and average temperatures, relative humidity, sunshine and maximum sunshine hours, wind speed, clear sky solar radiation (Rso), (75% of solar radiation in the upper atmosphere), the evapotranspiration was predicted. The results show that Ranker method with Relifef-Attribute-Eval in Naï ve Bayes, J48 and LMT method had the lowest error. So maximum sunshine hours, maximum and average temperatures were found to be the most effective parameters for prediction of evapotranspiration. Using feature selection algorithm can be useful to predict of evapotranspiration in regions with limited data and save time and money.

Aerosols play an important role in the climate system of the atmosphere. These atmospheric particles are directly affected by changing radiation exposure by diffusing and absorbing different wavelengths and indirectly by changing the optical properties and the durability of the clouds, and the optical properties of the aerosols, such as aerosols optical depth (AOD), are critical in understanding the effects of atmospheric aerosols on climate change and biogeochemical cycles. Therefore, in this research, the ability of radiation transmission model and MODIS images was evaluated to estimate the aeroeses optical depth in Persian Gulf. MATLAB was used for images processing of the images with resolution of 500 m at 5×5 networks. The evaluation of aerosoles optical depth data was performed by using AERONET stations with Pearson correlation, RMSE and RMSD indices. First results of the algorithm implementation showed the ability of model to simulate the aerosols optical depth. Modeling results showed that the algorithm is correct and according to spectral reflectance data for effective radius of the LUT tables, values simulated for aerosols optical depth. The results of evaluation showed that optical depth values obtained from the images has significantly correlation with the measured optical depth in AERONET stations. So that, amount of correlation calculated form 29 June 2013, 14 July 2014 and 6 October 2015 in the band of 1. 243 is 0. 96, 0. 94 and 0. 98 respectively, and for the band of 1. 643 is 0. 99, 0. 98 and 0. 98, respectively which shows a good trend between the measured data, RMSE and RMSD indices were calculated in these days less than 0. 15 and less than 0. 06, respectively. It can be concluded that simulations accuracy is appropriate in these bands.

Shifting aeolian dunes damage to infrastructure in Sistan plain. Accordingly, distribution, morphology and fixed and unfixed status of sand dunes in erosive corridors were surveyed by using satellite images and field investigation. Mean wind velocity, average seasonal and annual sand drift potential, resultant drift direction, resultant drift potential and unidirectional index (RDP/DP) were calculated using hourly wind speed and direction data in six meteorological stations around Sistan plain. In addition, temporal and spatial variation of wind energy weremapped using Kriging geostatistical method. The results show that activity of sand dunes matched wind of 120 days which lifted sediment from the dry beds of Hamoun Lake into 4 erosive corridors based on topography which forms Registan sand seas in the southwest Afghanistan. The types of dunes are Barchans, transvers and sheet which is formed by unidirectional wind. The DP decreased from northwest to southeast of region and the value of drift potential in Zabol station was calculated 2516 vector unit that it is one of the highest values in inland deserts of the world.

In this study, land degradation in Isfahan province in the period of 2001-2014 was monitored using trends analysis in terms of two indices of NDVI and RUE. To do this, MODIS satellite images with MOD13A2 code was used to investigate the vegetation degradation and for calculating the RUE, which is obtained from the NPP to rainfall ratio. The MODIS images with MOD17A3 code was used to calculate NPP and Kriging method was applied for obtaining rainfall map. The results showed that NDVI had an increasing trend while RUE had a decreasing trend based on annual rainfall. Evaluation of land degradation in the time period (2001-2014) and comparing the regression relationship between the two indices of NDVI and RUE in different land uses (agriculture, rangeland, forest and desert) of the study area showed that RUE trend was increasing in agriculture, rangeland and forest land uses, so that in 2001, the value of this index in the mentioned land uses was 0. 2, 0. 142 and 0. 149, respectively and 0. 61, 0. 099 and 0. 106 in 2014. In the desert regions, the trend of the two indices was decreasing, so that the value of RUE in 2001 and 2010 was decreased by the factor of 0. 097 and 0. 2131 g c m2 per year, respectively. Based on the results, it can be seen that the ecosystem of the study area is degrading.

This study investigated the effects of different concentrations of salinity stress on some morphological and physiological characteristics of Ammodendron persicum using a randomized complete design with four replicates. The salinity factors were control, salinity concentrations of 2. 4. 8 and 12 ds/m and the results showed that salinity significantly affected on all morphological characteristics of the plant. The salinity decreased stem diameter, the number of leaves, stem height, wet and dry weight of aerial parts and increased wet and dry weight of root. The results also showed that salinity increased the amounts of proline in which the highest amount of proline measured in salinity of 12 ds/mand was equal to 0. 046 mg/g and the lowest amount measured in control and was equal to 0. 022 mg/g. The highest amount of soluble sugar measured in salinity of 12 ds/m and was equal to 0. 75 mg/g while the lowest amount measured in control which was equal to 0. 63 mg/g. Increasing salinity also increased the amounts of chlorophyll a, b and total chlorophyll. Increasing salinity decreased percentage of Nitrogen and the highest amounts of N measured in control (equal to 2. 13%) and the lowest found in 12 ds/m (equal to 1. 57). Increasing salinity decreased also the amounts of K+, P+, Ca++, Mg++, and K+/Na+ and increased the amounts of Na+. It is concluded that Ammodendron persicum is not resistant to salinity and would not have suitable growth in soil with salinity more than 2 ds/m.

Drought with its effects on the performance of agricultural productions, water resources and vegetation cover accelerates the expansion of desertification. One of the methods for drought study and its devastating effects is monitoring and mapping of drought using meteorological indices and remote sensing techniques. To determine the impacts of drought on vegetation cover changes, the intensity of the drought was determined using the annual drought indices (i. e. the annual SPI and RDI). For drought indices mapping, five interpolation methods were used and compared. Then, the annual and seasonal average of NDVI was calculated using the MODIS 16-day NDVI time series from 2000 to 2014. The relationship between the drought indices (SPI and RDI) and the NDVI in different vegetation coverages was evaluated in Yazd province. According to the zoning of drought indices, Yazd province has been in a state of severe drought between 1999-2000 and 2007-2008. Evaluation of correlation results between different vegetation coverages type in Yazd province with drought indices showed that the semi-dense forests, woodlands, shrub-land, and pasture were severely affected by drought while the planting forests, agricultural areas, and gardens were less affected. Based on the results of coefficient of determination (R2) maps, the highest correlation between the average of NDVI in the spring and the annual drought index (SPI) was founded in the semi-dense forests, woodlands, shrub-land, and pastures grade 2 and 3 with the R2 of 57, 50, 44 and 41 percent, respectively. Likewise, in the summer, the semi-dense forests, pastures grade 1, 2, and 3, woodlands and shrubbery zones, had the R2 of 62, 51, 41, 35 and 44 percent, respectively.

Due to some factors such as limitation of water resources, increasing demands in all aspects and also the impact of climate changes, the optimal management of water resources and their efficient use is an essential task. To achieve this effective management, appropriate water resources planning can be utilized. One of the basic parameters of the water management is the accurate calculation of water balance components. Present study was conducted to determine the effects of Haloxylon aphyllum artificial forest on groundwater extraction from Yazd-Ardakan aquifer. To achieve this, numbers of Haloxylon aphyllum shrubs were counted using JMicrovision software on the preprocessedGoogle Earth images. Then considering annual water needs of Haloxylon aphyllum-obtained from lysimetric data of previous studies-and number ofHaloxylon aphyllumcounted fromGoogle Earth images, water extraction of planted forest was calculated. In next step, using GMS 8. 3 andModflow model, the aquifer balance and effective storage coefficient were obtained for calculating groundwater extraction of Haloxylon aphyllum in Yazd-Ardakan aquifer. The results showed that the 4423640 Haloxylon aphyllum existed in the Yazd-Ardakan plain and there is 56 million cubic meters of shortage in reservoir capacity. The amounts of groundwater extraction byHaloxylon aphyllum forest was estimated about 1. 614million cubic meters per year. The positive role of reforestation in relation to the dust storm damage reduction rounded and included the use of water should not be ignored. The results of the research are applicable for water resources and water use management of plantation forests.

Desertification means land degradation in arid, semi-arid and dry sub-humid regions as a result of various factors, including climatic variations and human activities. In this research, the study area with an area of 136 thousand hectares located 20 kilometers far away from east Isfahan was selected. Due to the proximity of this area to Isfahan city and the impact that desertification phenomenon on the city, studying the desertification in this region is of great importance. To assess the current status of desertification, the multi criteria Analysis and MEDALUS model was used. For this purpose, in the first step and based on the local situation, six qualitative criteria, including climate, soil, groundwater, vegetation, soil erosion, desertification management and policy evaluation were considered. These indices have been standardized and quantified based on their effect on desertification in the frame by scoring 100 to 200. The qualitative value of each criterion has been obtained by multiplying the weight of the Analytic Hierarchy Process (AHP) and integration of layers based on the weighted linear combination. Finally, the desertification status map has been acquired through multiplying weight to the layer value of each criterion and integrating layers according to the method of weighted linear combination in Geographic Information System (GIS). According to the results, 35. 49% of the area of the region falls in a severe class and 64. 5% falls in very severe class of desertification. Besides, the climate criterion with a weight of 0. 29 has the greatest impact on the phenomenon of desertification and then it goes to the management and soil criteria with weights of soil 0. 23 and 0. 21, respectively. Therefore, to assess desertification and executive programs to deal with it in the region, considering these criteria are of great importance.

Hormzgan province located in the southern Iran has suffered from water resources shortage and high water losses in the agricultural sector have been led to the serious water crisis in this province. This research aims to use of virtual water in the arid regions considering the irrigation efficiency. The highest amount of virtual water was found to be 98. 83 for citrus fruit production among the horticultural products, 43. 7 for barley among the agricultural products, and 5. 123 for potato among the cucurbits. The results of exploring the virtual water business showed that the amount of imports and exports of virtual water of the studied products in Hormozgan province was 20434. 2 and 1120. 9 million M3 respectively. Also, the volume of virtual water of vegetable group is less than 0. 07 m3/kg of the product. So, vegetables are placed in the low-consumption with high productivity group. Against, the palm is placed in the high-consumption group due to 3. 8 m3/kg volume of virtual water. Results of the value of virtual water of products showed that the values of exported and imported volume of virtual water are 2122. 8 and 133. 1 million Rials, respectively. Since, Hormozgan province has a little potential in the use of green water, therefore, it is suggested cropping pattern in the province with regard to water supply of green products resistant to water stress, with an emphasis on production with less water requirement and profits, reduce pressure on water resources to achieve the long-term food security and constant agriculture.