Desert Management
Year:2019 | Volume:6 | Issue:12 |Papers Count:8

In water systems, precipitation is considered as input and evaporation as the output of the system. Water availability can be estemated from the relationship between these two factors. Therefore, evapotranspiration is the most important factor after precipitation in hydrological cycle. Evapotranspiration is influenced by climatic parameters such as temperature, wind, humidity and sunshine hours. In this research, changes in PET and effective climatic parameters, influencing on PET changes including temperature, wind, humidity, and solar radiation were investigated. For this purpose, PET in 14 weather stations of Yazd province were calculated using the FAO-Penman-Monteith method. Due to the lack of sunshine hours data in some stations, regeneration of the incomplete data was done by using regression method. Due to the lack of wind speed data at some stations, their reconstruction by using data from other stations was done by applying three methods of Inverse Distance Weighted, Kriging and Cokriging. After calculating potential evapotranspiration, PET data were zoned and their monthly and annual trends tested by Mann-Kendall test. Despite occurrence of climate change and increasing of temperature in 13 stations out of the 14 stations, it is expected an increase in potential evapotranspiration in past few decades, while, there is a decreasing trend in PET. Investigating on the effective parameters in potential evapotranspiration showed that wind speed has declined in the last few decades, and despite of an increase in temperature, potential evapotranspiration rate reduces in 64. 3% of the stations. General trend of evapotranspiration was-0. 86 in this period, which indicates a decrease in evapotranspiration in the Yazd province.

Understanding of distribution of plants and analyzing their spatial pattern reveal the interactions of plants and environment. Nebka as an indicator phenomenon of plant-sediment interaction, plays an important role in protecting of vegetation and sand stabilization. The aim of the present study was to evaluate the interaction of Nebka and plant based on a field study, measuring the morphometric parameters, and precise point positioning. Therefore, 322 Nebkas and 119 plants were determined in the northern region of Aq-Qala, Golestan province. In order to investigate and determine the spatial pattern and interactions of Nebkas and plants, and impact of soil parameters on their distribution pattern, univariate and bivariate functions including g and mark correlation functions were used. The pair correlation function showed that spatial pattern of plant at distance of less than 23 m was irregular. This means there is no competition between plants at distance of less than 23 m. Furthermore spatial pattern of Nebka was irregular at distance of less than 23 m. Bivariate g function at distances less than 50 m indicated positive correlation between plant and Nebka. Therefore, all plants and Nebkas have a positive impact on formation and distribution of each other. Results of the MCF function with 95% probability showed that soil properties such as EC, pH, OM, SAR, and skewness of Nebka sediments influence the Nebka’ s pattern in the study area.

Surface albedo is one of the key controlling geophysical parameters in surface energy budget research and environmental and climate studies. As an efficient tool for monitoring earth surfaces, remote sensing is widely used for estimating albedo over recent decades and various algorithms of satellite data have been developed to estimate albedo. Up to now, albedo has been estimated using different types of sensors. This study presents procedures for computing of albedo using OLI sensor Landsat 8 data in different geomorphology facies, arable soil and asphalt in the Yazd-Ardakan Plain. In this way, required data from each nine images metadata of Landsat 8 were extracted for summer and autumn, 2017 and then albedo was calculated using meteorological data. Results showed that there is a difference between values of albedo in different geomorphology facies. Surface albedo average of clay land, pavement, sand dune, bare land, sand sheet, arable land and asphalt are 0. 30, 0. 22, 0. 24, 0. 26, 0. 24, 0. 23 and 0. 24, respectively. The highest calculated albedo is related to clay land, while the lowest is observed in desert pavement facies.

Wind erosion is one of the most important natural processes in arid and semi-arid regions. In recent years, due to lake drying, dust producing has been increased from lakes and wetlands surfaces. Maharloo Lake, as one of the most important saline lakes of Iran, dried up in recent years. This research aims to study the susceptibility of Maharloo Lake sediments to wind erosion and determining of direction of the Lake surface dust movement. At first step, texture of the sampled sediments were determined. Next, direction of the dominant and erosive winds were determined by drawing wind and storm rose graphes and concentration of dust was calculated over a period. Results of sediment granulometry and hygrometry showed that more than 60% of the Maharloo Lake sediments were silt. Results of wind and storm roses showed that the direction of dominant wind is west and northwest; while the direction of erosive wind is western. According to the results of dust concentrations from two TSP and PM 2. 5 samplers around the lake, it is derived that the amount of dust collected from the lake’ s sediments is higher than normal. Also, based on the dominant wind direction, created dust would affect mostly villages around the lake and also, Sarvestan Township. Therefore, in regard to the percentage of particles frequency containing Maharloo Lake’ s sediments and their high sensitivity to wind erosion, this challenge described in advanced will soon become apparent to other cities located in Fars province and even to other adjucent provinces.

Identification of suitable sites for solar power plant establishment in arid regions is very important for using high potential solar energy. This study aimed to identify more important factors influencing site selection for solar power plant establishment and to determine highly suitable sites to establish solar power plants in Sistan region. Influencing factors on site selection were selected based on experts’ opinion using Analytic Hierarchy Process (AHP) with regard to climatic, geographic, socio-economic and environmental variables. Paired comparison of criteria and sub-criteria was performed using fuzzy analytic hierarchy process to determine the weight of each criteria. After preparing of the layers of criteria using GIS teqhniques, weights of criteria were multiplied in their corresponding layer. Finally, site suitability map for solar power plant establishment in Sistan region was prepared at five classes through overlaying of layers. Based on results, 4. 8 percent of Sistan region, which is located in the southern part of Zahak and Hamoun cities and eastern parts of Nimrouz city, has an excellent suitability for solar power plants establishment. In addition, 36. 6% of the study area has a good suitability, 0. 5% has a moderate suitability and 18%, which is located in Bandan and Sefidabeh areas, has a poor suitability for solar power plants. Furthermore, sunny hours, temperature and elevation parameters because of having more weight, were identified as the most important criteria. Results indicated that about 45% of Sistan region has high suitability for solar power plants establishment. Therefore, the investment risk of the solar power plants in Sistan region is low. Maximum utilization of solar energy can provide a favorable condition for economic development and increasing the survival of people in Sistan region.

One of the most common and destructive phenomena in arid and desert regions is dust which can have negative effects on the environment. Eastern half of the country has always been exposed to this phenomenon due to its geographical location and even to 120-day winds. The present study aims analyze and Clustering dust storms in eastern of Iran. For this purpose, hourly data of dusty days, phenomena code, horizontal visibility, wind direction, speed and current weather of 17 weather stations in eastern Iran during period of 1986 to 2016 were used. Dust storm codes were used for statistical analysis. Then, trend type and value were detected using Mann-Kendall (MK) and Sen's estimator tests Using WRPLOT View, dust rose of the area was drawn. Results showed that the frequency of dust storms in July was the highest and the lowest occured in December. The intensity and distribution of dust in the south-east of the region was more than other regions. Results of MK test suggested a significant increase in southeast, central and northwest stations, while most stations in north part of the region showed a significant decrease. Dust rose results also probes the direction and speed of winds causing dusty storm were different in east and west of the region. The direction of wind causing dusty storm in the eastern half is between 70° to 300° , while in western part of the region, wind blows between 260° to 280° geographic coordinate system at speed of more than 11 m/s.

Net primary production (NPP) is one of the most important factors in ecosystem's function, which is affected by biological and climatic factors. The main objective of the current research was to investigate the potential of the CASA (carnegie-ames-stanford approach) model in determining the spatial and temporal distribution of NPP in rangland types of arid regions of Isfahan province using MODIS and Landsat. For this purpose, satellite and climatic data such as rainfall, temperature, monthly and sunny hours, were used. The NPP was modeled on two Landsat and MODIS scales and correlations between field measurements and CASA model were investigated based on rangeland conditions and vegetation types. Results showed that the highest plant production in the region was during the March-May months. Crrelation between CASA model with field data occurred in MODIS was higher than Landsat data. Based on the relations, the values of NPP and LUE (light use efficiency) were investigated in the region. The NPP spatial distribution and LUE values indicated that the amount of annual production and photosynthesis efficiency were decreased in degraded rangelands (poor and very poor conditions) compared to fair rangeland condition. The highest and lowest amount of NPP observed in Artemisia sieberi – Zygophyllum Spp (9. 35 g C/m2 y-1) and Annual grasses-Annual forbs (0. 2 g C/m2 y-1), respectively. The amount of NPP and LUE in shrublands and annual plant types were higher than bushlands. Results of this research probes the importance of biological classification, climate and scale of study in NPP modeling. Moreover, the stratification of rangelands based on life forms and range conditions has principal role in accuracy of the NPP estimation.

Environmental pollution as a desertification consequences, is one of the most important challenges in human societies. Nitrate and phosphate are two important pollutants, which are created from chemical fertilizer and cause water resources pollution. There are different techniques for remediation, but due to the sensitive and fragile propertise of deserts ecosystem, phytoremediation process is a natural remedy utilized by agricultural system. This study aims to assess the phytoremediation potential of Ailanthus altissima Mill. and Fraxinus excelsior L. for removal of Nitrate and phosphate in water by factorial experiment in randomized complete block design. Firstly, a total number of 96 trees from the two species were planted in Isfahan University of Technology. In the current study, three levels of phosphate (5-10-50 mg/L) and nitrate (5-10-50 mg/L) for each of the species were and a blank sample with three were considered replicates. Nitrate and phosphate pollutants were investigated in three densities of 5-10-50 mg/L in 3 replications. Afterwards, the level of nitrate and phosphate removal were measured. Results show that nitrate removal levels in 5, 10 and 50 mg/L concentrations in first week by A. altissima are 74. 53, 75. 23, and 79. 95% and by F. excelsior are 79. 04, 80. 65, and 83. 97%, respectively. Likewise, phosphate removal in 5, 10 and 50 mg/L concentrations by A. altissima are 74. 10, 77. 18, and 82. 81% and by F. excelsior are 74. 16, 79. 87, and 83. 56%, respectively. There is a significant difference between A. altissima and F. excelsior in removing nitrate and phosphate.