| چکیده انگلیسی مقاله |
1- Introduction
One of the most important factors of desertification is wind erosion, whose importance and danger on a global scale is no less than water erosion (Refahi, 2010). The emergence of sand dunes in some countries such as China is one of the examples of progress and development of the desert, and in some countries exposed to desertification, this process is less important and other processes such as salinization, destruction of plant resources, etc. are important. It can be said that one of the natural forms and symbols of desert areas is the sand dunes that occupy a considerable area of the desert compared to other natural forms of the desert (Mashhadi et al. 1385). The total area of these hills and sandy areas that occupy or threaten the outskirts of cities, villages, communication lines of the country and infrastructure facilities is estimated to be 13 million hectares, of which about 5 million hectares are active hills. And the rest includes fixed or fossilized hills (Khatsasi et al., 2014). One of the most obvious characteristics of sand dunes is their movement, which causes the loss of non-economic land uses, natural vegetation, etc. to increase the movement and displacement of the dunes. (Dang et al., 2000). Therefore, the timely and correct identification of the changes of such complications creates a basis for a better understanding of the connections and interactions between humans and natural phenomena for better management of resources. Having three wind erosion crisis centers, namely Yaztepe wind erosion crisis center and Mohiniran border post, Gonbadli and Abmal wind erosion crisis center and Samad Abad wind erosion crisis center, in recent years it has been severely affected by wind erosion and expansion There are sand dunes that have caused many problems for people.
3- Results
Based on the studies of the atlas of wind erosion centers in 1379 by the country's forests and pastures organization, the studies of three critical wind erosion centers named Yaztepe-Gonbadli, Abmal and Samadabad have been identified in it, and each center is divided into three regions., transportation and sedimentation have been separated into low to high intensities. These studies are related to the last 20 years, which were compared and analyzed with the areas extracted in 2000 and 2005. The sand areas prepared in 2000, 1250 square kilometers and in 2005, 976 square kilometers have a good match with the locations of wind erosion crisis centers. In the review studies of the critical centers of wind erosion of ferns, which was carried out in 2019 by the engineers of the Tak Sabz consultant, the critical center of wind erosion of Chale Zard was identified and it was suggested by this consultant to prepare additional studies in the areas of wind erosion in 2010. In this research, which is related to the last ten years, the direction of the sandy areas is towards the center of Chale Zard, and this confirms that despite the prevailing wind direction in the area, which is from the northwest to the southeast. is, the advance of the sand flats is towards the west of the region, and it is possible that the only reason for that is the presence of the Tajen river and the agricultural lands in the east and northeast of the region, which hinder the advance of the sand flats. It goes parallel to the direction of the prevailing wind in these areas. The area of sandy areas in 2010 has increased by seven percent compared to 2000. The area of sandy areas in 2015 is 1356 square kilometers and its front is towards the northwest of the studied area. As mentioned earlier, there are three critical centers of wind erosion in the region, and identification studies and suggestions for preventive and curative measures have been presented in these studies. Therefore, priority has been given to parts of the region that were not previously in the territory of the city's sandy areas, and according to the research conducted, they are currently located in this area. Based on this, in the north, north-west and west part of the study area up to the location of Samadabad wind erosion center, considering that the majority of the area is poor pastures, there are 21 villages, 177 kilometers of communication roads and 10 km of railway is located in this area, it is considered as the first priority of management planning to prevent the development of sandy areas. The second priority in the central part of the studied area is between the critical foci of wind erosion from Gonbadli-Abmal to Samadabad, which is due to the conversion of pasture lands into wet fields, wrong agricultural patterns, lack of management and excessive livestock grazing, causing pastures to become plains. It has become sandy. If management plans are not implemented to control desertification, in the not-too-distant future, critical conditions will be reached on a wider scale, which will lead to transregional environmental problems. The priority of three areas is according to the location of the critical centers of wind erosion, Yaztepe-Khangiran, Gonbadli-Abmal and Samad Abad, and restoration projects for the harvesting, transportation and sedimentation areas of these centers have been presented in past studies.
4- Discussion & Conclusions
The results of this research indicate the different changes of sand areas in 5-year periods. Although the area of these zones has increased during the studied period, which is 15 years, but in some periods, due to different climatic conditions, the area of the zones has decreased. According to the results of this table, the area of sand dunes in 2000 was equal to 125,000 hectares, which reached 135,000 hectares in 2015, and almost 10,000 hectares have been added to the area of these zones, but the area of sand dunes in the year it decreased in 2005 and 2010 and increased in 2015. The area of wind deposits decreased in 2005 and 2015 and increased in 2010. All these results confirm the non-uniformity of changes in these areas in different years, which depends on various factors, including the climatic conditions of the region. Also, the prioritization of the sandy areas in Sarkhes city was based on the threats to the resources and strategic areas of the city, which include population areas, important regional facilities, touristic, cultural, economic, agricultural areas, and communication routes. Was performed. According to the areas of wind erosion in 2015, a total of 24 km of Sarkhs-Mashhad railway, 295 km of communication roads, 25 villages, 4801 hectares of hand-planted forests in the region and important areas such as Almas Airport, Nazbiran Refinery, Khatun bridge and the special area of ferns were located in these areas. |