مجله مدیریت بیابان
پیاپی 19 (پاییز 1400)

This study aimed at predicting the effect of climate change on the geographic distribution of Thymus kotschyanus Boiss and Hohen in Mazandaran province. Species presence data were recorded via the Global Positioning System (GPS). The distribution of T. kotschyanus Boiss and Hohen under current and future climatic conditions 2050 and 2070 (1428- 1448 Solar) applying  two scenarios of RCP 4.5 and RCP 8.5 climate change by using the GCM data series of general circulation models BCC-CSM1-1، CCSM4 and MRI-CGCM3  and the five species distribution models such as Generalized Linear Model, Generalized Additive Model, Classification Tree Analyses, Generalized Boosting Model and Random Forest methods was investigated. For this purpose, layers of environmental factors, including six bioclimatic and two physiographic variables, were used as inputs to species distribution models. Among the environmental variables, precipitation seasonality, precipitation in the coldest quarter, and isotherm had the greatest impact on habitat suitability. The assessment of the modelling indicated that the Generalized Additive Model and Generalized Boosting Model had better predictions of climate habitat than the other models. The results also indicate that climate change will change the range size of the T. kotschyanus Boiss and Hohen, and will move toward higher elevations in the future. The results of the present study may be used to plan habitat protection for the medicinal species of T. kotschyanus Boiss and Hohen, as well as its restoration and rehabilitation in the vast regions of the country.

Wind erosion is one of the problems in arid and semi-arid regions that is associated with the process of detachment and transportation of soil particles by wind. The Wind Erosion Risk Index is a framework for modelling wind erosion that examines the sensitivity of land to wind erosion based on a set of surface and climate thresholds. The purpose of the study is to assess the risk of wind erosion in various geobiofaces at Abarkouh plain, Yazd province, using the WEHI model from 2003 to 2017. Three factors including frequency of erosive winds, percentage of bare land and soil surface moisture were used to run the model. Wind erosion risk map was produced under three categories: low, moderate and severe. To evaluate the effectiveness of the model, aerosol optical depth (AOD) data were used that confirmed the accuracy and significance of the model (α=0.01). The results showed that 107,369 ha of lands in the severe wind erosion category was increased. Wind erosion is widespread in the study area, particularly in the geobiofaces of the salt-lake and saline lands. The risk of wind erosion is reduced only on near-dense farmlands. This may expose the land upstream of the study area to the hazards of salt storms given biological, economic and social threats.

Selenium (Se) and silicon (Si) are identified to affect plant physiological attributes and yield parameters. Se and Si’s effective roles in reducing various environmental stresses in plant of Origanum vulgare L. are unknown and need to be investigated. This study aimed to examine the role of Si and Se application on O. vulgare under drought stress and the effect of these two elements on physiological traits and yield parameters of O. vulgare. The impact of the foliar spraying of Se and Si under drought stress conditions was studied through a split factorial experiment with three replications in greenhouse conditions at the Yazd University. Drought, as the first factor in three stress levels of 30, 70 and 100% of field capacity, and nutrient factors including Se in three levels of control, 15 and 30 mg/l, and Si in three levels of control, 150 and 300 mg/l were sprayed. Foliar spraying of Se 30 mg/l had a significant effect on the increase in proline, soluble sugar, chlorophyll, carotenoids, phenolics compounds, and fresh and dry shoot weights. The foliar spraying of Si 150 mg/l had a significant effect on the increase in proline compared to the control traits. The change in foliar spray quantity of Si has no significant impact on changes in yield parameters. The combined foliar spraying of Se and Si to reduce the effects of drought stress has been more effective than applying just one of these elements in improving the physiological attributes of O. vulgare. The solution of 30 mg/l Se and 15 mg/l Si has a higher yield under drought stress conditions of 70% of the field capacity.

Nowadays, desertification and land degradation are among the most important environmental chalenges caused by various factors, including climate variation and human activities, especially in arid and semi-arid regions. Therefore, understanding of the desertification status is essential for future management and planning. In this regard, using remote sensing indicators to prepare basic desertification maps and its monitoring can be efficient. In this study, Topsoil grain size and albedo indices were used as indicators to identify desertification in the center of Khuzestan province. After constructing the above-mentioned indices using Landsat ETM+ sensor image, the values of 411 randomly selected samples on the images were used to construct the Albedo-TGSI feature space model. The correlation between the variables was 0.83. The DDI desertification degree equation is then obtained based on the slope of the fitted line. In the next step, by applying natural break classification on the DDI index, different levels of desertification and the break values ​​were obtained for random samples. These break values ​​are then applied to the whole study area, and finally, the 2018 desertification status map was obtained. Results indicated that about 70% of the study area fell under the severe and high desertification intensities, whereas 18.3%, 8.3% and 4.1% fell under the medium, low and none desertification grades respectively. The accuracy of the produced map with a kappa of 92.1% and an overall accuracy of 94.3% showed that the feature space model is a useful and robust tool for extracting desertification degrees in barren lands or areas with extremely low vegetation coverage.

Community participation in desertification projects lowers costs and makes projects more effective. Through strategic policies for the restoration, conservation and sustainability of natural resources, the government is implementing programs, and individual, cultural, social and economic factors play an effective role in increasing the participation of villagers in desertification projects. The objective of this study was to study and prioritise factors affecting the participation of villagers in Mohammad Shahkaram area of Zahak city, where desertification projects have been implemented in its northern zone. Data collection tool is a questionnaire. According to Cochran's formula, the number of samples required was 358 questionnaires and for questionnaire reliability, 30 questionnaires for the sample were tested in advance. The analysis of the data was based on descriptive statistics and inferential analysis. Results of the AHP method and multivariate regression analysis showed that the independent entered variables can predict 57% of the variables related to the village participation rs in desertification projects. Among the variables studied, age and work experience of individual factors with a Pearson coefficient of 0.216 and local responsibility from social factors have the highest correlation with participation rate.  Maintaining desertification projects in the region puts in the first rank, and sociocultural index factors have a higher priority than variables dependent on participation in desertification projects than economic index and planning.

In many areas of Iran wher water is scarce, including the western Khorasan, people have understood the importance of water and soil resources. They have made great efforts to protect them, and they also gained valuable experiences. The use of these experiences in the construction of the Bandsars allowed optimizing the water and soil resources and the localization of  watershed management operations which will improve the effectiveness of those operations. The bandsars cause the sedimentation of suspended particles by controlling the flow rate, and consequency, in addition to the increase in soil fertility, improve the recharge of groundwater, vegetation cover and desertification control. This research studies the effect of the use of flood in bandsars,  located in the south of the city of Sabzevar on soil fertility using both field and laboratory methods. To achieve this, 5 Bandsars sites were selected in the study area, and in each site 3 soil profiles inside the bandsars and also 3 profiles outside the Bandsars with 60 cm depth were digged. The soil samples were collected from three depths of 0-20, 20-40 and 40-60 cm. Soil samples were transported to the laboratory and the amount of organic mater, N, P and K were measured. Results were analysed using t as well as Dankan tests. Results showed that the values of the fertilizing elements such as organic mater, N, P are different between inside and outside the bandsars, and are higher inside the bandsars comparing to the related outside areas. Although this difference is not statistically significant in some cases, it can be concluded that Bandsars improved soil fertility.