مجله مدیریت بیابان
پیاپی 22 (تابستان 1401)

Desertification, as a complex process, is a serious threat to the environment in many parts of the world, especially in arid regions. With accurate knowledge of the factors influencing the spread of desertification and appropriate management strategies, the impacts of this process can be controlled or reduced. The aim of the current study was to identify and assess indicators and indices of desertification for the assessment and mapping of sensitive areas of the Kavir-e-Namak basin in Khorasan Razavi province, to desertification. In this study, an assessment model of sensitive areas to desertification (ESAs or MEDALUS), available data based on field studies in 2021, was used. At first, five criteria including soil, climate, vegetation, erosion and human activities were identified as the main criteria for desertification.  Then, on the basis of the opinions of over 40 natural resource experts, the indices of each criterion were classified, weighted and assessed. The quality of each criterion was determined by the calculation of the geometric average of the indices. Finally, the map of areas sensitive to desertification in the study area was produced using GIS. The identification of management strategies was conducted using the Delphi approach and distributing a two-cycle questionnaire based on scenario planning and future studies. The results showed that among the criteria for desertification in the study area, climatic criteria, human activities, soil and erosion with values ​​of 1.54, 1.53, 1.51 and 1.50, respectively, are the most important criteria followed by the vegetation criterion with a value of 1.45 as a next effective criterion of desertification. Results indicate that 12% of the study area are in the fragile class, and approximately 88% in the moderate to severe critical class.  Based on scenario planning and method of futures studies, the best and worst scenarios in four different categories including adaptive management and organizational cohesion, economic and social empowerment of local communities, educational development, culture and advertising, and participatory implementation of natural resource projects as comprehensive management strategies were developed.

Although land degradation is a worldwide challenge and a destructive phenomenon, little studies have been done on the application of new numerical methods (data mining and statistically), for spatial simulation of this phenomenon and identification of areas sensitive to land degradation. The aim of this study is to spatially simulate land degradation in the Qazvin plain using the frequency ratio model to identify areas prone to land degradation. For this purpose, using the trend of changes in net primary production during the years 2001 to 2020, the points of occurrence of land degradation in the Qazvin plain were determined. Approximately 70% and 30% of the points were used to prepare the land degradation vulnerability map and validate the model's efficiency, respectively. For this research, 15 parameters affecting land degradation (directly and indirectly) including temperature, rainfall, slope, aspect, elevation, EC and SAR of ground water, ground water level, annual ground water decline, land use, normalized difference vegetation index, normalize difference salinity index, vegetation soil salinity index, normalized difference moisture index, and visible and shortwave infrared drought index, were introduced into the model as predictors factors or independent parameters. Finally, using the area under the ROC curve, the effectiveness of the frequency ratio model for spatial simulation of land degradation was assessed. The map of land degradation susceptibility shows that the areas prone to degradation are located in the northeast, north, northwest, west, southwest, and south of the Qazvin plain, which mainly includes good, moderate and poor rangelands. For the land use parameter, the highest frequency ratio was associated with the sum of good, moderate, and poor rangeland (5.66). The value of AUC = 0.7 indicates the good performance of the frequency ratio model in spatial simulation of land degradation.

Wind erosion and dust storms are among the most important natural hazards and have negative impacts on environment and people. The Hamoun international wetland- located in the southeast of Iran and southwest of Afghanistan, at the estuary of the Helmand River – due to the severe droughts during the last three decades has become the main source of soil erosion. The purpose of this study is to investigate the sensitivity of wind erosion in the Iranian section of the Hamoun wetland as the Hamoun wildlife refuge. Byliterature reviewing and using experts’ knowledge, 15 effective criteria in the phenomenon of wind erosion were determined and weighted by using AHP method. The weights analysis showed that among the criteria, vegetation cover with 0.13 had the highest weight. Using satellite images related to November 2021, the SAVI vegetation index was prepared as an index of the amount of vegetation cover.  To prepare the soil criteria maps, 135 pints of surface soil were taken and transferred to the lab. After determining the criteria value in each sample, the map of each criterion was prepared using the IDW method. The criteria were standardized using the FUZZY method, and then combined by applying the calculated weights and using the weighted linear combination method to prepare the wind erodibility model. The prepared model was classified into five erodibility classes. To assess model accuracy, the wind erosion threshold speed was calculated by installing a portable wind tunnel device at 40 sites. The resulting figures were classified into five levels according to the erodibility classes, and compared with the corresponding erosion class of the wind tunnel sites.  An overall accuracy of 81% for the prepared model shows capability of this model to prepare an accurate wind erosion model.

Iran's location in the drylands belt has increased the frequency of dust storms in western parts of Iran, particularly the city of Kermanshah and negative environmental impacts. Arid lands, as one of the main sources of suspended dust in the atmosphere, face problems such as sandstorms, high levels of dust particles and reduced visibility, which are major climate problems in the country, especially in the border provinces. The purpose of the present study is to investigate the performance of a numerical model between the meteorological-chemical atmosphere scale called WRF-Chem model in the simulation of the concentration of suspended particles in Kermanshah region. By comparing the spatial distribution and concentration of suspended particles, meteorological parameters simulated by the model, and the available observational values for PM10 particles in Kermanshah, the efficiency of the WRF-Chem model was evaluated. The results of the simulation of PM10 particles for the studied days showed that the central and western deserts of Iraq, Syrian desert, Kuwait and northern Saudi Arabia are the main source of dust storm. Due to the logical correlation between dust particle emissions and temperature and relative humidity parameters, accurate estimation of these parameters is very effective in PM10 particle simulation accuracy. Based on the analysis of the PM10 variables, temperature and relative humidity and the plotted graphs and their comparisons, a favorable agreement was achieved between the simulated and measured values for PM10, temperature and relative humidity.

In addition to the increase in prone areas to wind erosion processes in western Azarbaijan province due to the drying of Lake Urmia, there is a growing concern regarding the intensification of dust storms. Considering the impacts of this phenomenon on the environment, public health, agriculture, and transportation sections, more detailed studies on its source, severity, and frequency is necessary. Therefore, this study was designed to assess the temporal and spatial changes of dust storm events using satellite data, to detect the dust source, and to analyze the factors affecting the occurrence of dust storms in western Azarbaijan province. Analysis of the number of dusty days using the MODIS-AOD product indicated that the years 2003, and 2008 to 2012 were the dust storm peaks during the period 2000-2020 at western Azarbaijan province. Most dust storm events have occurred in summer and spring seasons, and monthly changes indicate the maximum dust storm between March and October. Trend analysis indicated that there was no significant trend in AOD and dust storm events. Among vegetation and climate variables, there is a significant relationship between AOD and wind speed (i.e., the correlation is about 64%). Spatially, dust storms occur more frequently along the shores of Urmia Lake (mostly in the east and south and slightly in the west).  Southern areas of the province reported a higher frequency of dust event than the central and northern parts of the province.  Due to the direction of the prevailing wind, it seems to be most affected by dust storms coming from the neighboring country of Iraq, however, the areas around the Lake Urmia are the inner source of dust storms.

The aim of the present study is to investigation the effect of different land uses (forest, rangeland, cane brake and bare land) on carbon sequestration and soil erosion in Jazink region located in Zahak city, Sistan and Baluchestan province. For this purpose, following the field evaluation of various land uses, soil samples were taken from at depths of 0-30 cm and 30-60 cm for each land use. Some soil properties including organic carbon, texture, bulk density, sequestered carbon and soil stability index (MWD) were measured according to standard methods. Data analysis was performed using one-way ANOVA analysis in a completely randomized block design, and the averages were compared by Tukey test at 95% confidence level using SPSS software. The results showed that the amount of bulk density at various soil depths in cane brake land use had the lowest of 0.992 and 0.956 gr/cm3, respectively, and in the bare land had the highest value about 1.59 and 1.61 gr/ cm3, respectively. Carbon sequestration in land use by cane brake was 3234.02 and 2455.32 kg/ha, respectively, and in bare land, it was the lowest around 1967.37 and 987.65 kg/ha.  Soil stability in the bare land was the lowest at 0.342 mm and the highest in the canebrake land use at 1.67 mm. Higher amount of carbon and organic matter in the soil and the lower bulk density indicates that the soil is more stable and resistant to erosion. In this region, cane brake and forest land uses have the highest degree of stability and carbon sequestration among land uses. These results can be very useful for decision-making and for choosing suitable management practices and desertification programs in arid areas such as this region.