IRANIAN JOURNAL OF RANGE AND DESERT RESEARCH
Year:2005 | Volume:12 | Issue:1 (18)|Papers Count:9

Desert as a biome of biosphere, resulted from atmospheric cyclones. It is obviously accepted by anyone, that desertification phenomenon, which is acquired under climate change and insufficient development of human activities, threaten environment. Without considering amount of efficiency of these factors on desertification, what it were not regarded under conditions our country, determination of real desert domain based on different environmental factors. At this paper, we tried to map the desert regions of Khorasan province using climatic factors. In order to reach the results, firstly, meteorological stations net of Khorasan, were identified and 85 station were selected. The local distribution of these stations as a point map was plotted using Ilwis software. Recent layer was used as a base map for other works. Continually, some of climatic factors for example coefficient of variation of precipitation, Demartonne aridity index, isohytes, isotherms, and etc, which reflected climatic characteristics of desert regions, calculated and analyzed for any station. Then, isometric maps of each climatic factor plotted using Surfer software. Finally different layers overlaid together using Geographical Information System and three zones released on final map. Inter zone with harsh conditions was contained real or natural deserts with over of 22 million hectare area and middle zone which is named Semi-desert, included desert and non-desert characteristics. Results showed that environmental factors varied gradually and desertification processes, were active on transition zone.

Systan plain is located in the east of Iran and has the fastest dust storms in the world. Existence of suitable water resources has caused dense population in comparing with other regions in Iran with high wind erosion features; so more investigation was needed in this area. Distinguishing the erosive wind directions is the first step in wind erosion control projects, which usually determined by wind data analysis, field work and aerial photo interpretation. In recent years progression in remote sensing technology raised new possibility to use especially high resolution Satellite images like aerial photos for this purpose. But multiplicity of MODIS images could be used as an advantage for storm tracing. So in this research we have used 4 MODIS images from June to August in 2001 for determining the average storm direction in 18 locations and compared with 17 observations on sand dunes and also wind direction in Zabol synoptic station. The results show that there are good agreements among storm directions on images with other observations. Nevertheless we showed 10-31 degrees deviation among these two groups of data near villages and agricultural fields, which demonstrate the effect of buildings, wind breaks and other barriers on deviation of general wind direction. We also showed 5-23 degrees differences range among storm direction in different images which assert wind direction change by time. So it is necessary to use more than one image for getting an average.

Sistan plain is located near Afghanistan neighborhoods. There are three lakes (Poozak, Saboori and Hirmand) in the Sistsan region. Natural and human ecology in Siststan affected by wind erosion and lakes function. Wind erosion is a big problem in Sistan, because all of human activities are affected by sundun transition and sedimentary. Every year many types of equipment must be used for decreases above problem. Suggested location of sand dunes transition and sedimentary can be used for solving problems. Two main objectives of this study are to investigate the use of satellite image data for detecting active dust storms to wind erosion for active dust storm detection, the satellite image data investigation includes those images collected by the Landsat Thematic Mapper (TM). Images collected by Moderate Resolution Imaging Spectroradiometer (MODIS) have been added, and analyzed these data. Results of researches shows that three places are located of sun dunes: Second is the contacting place located of Far Rood River with Savory Lake, contact of Savory with Harman Lake and third is west of Harman.

Application of petroleum mulches for soil stabilization and sand dune fixation dates back to the early 1900s. The number of methodological research reports on these subjects, however, is very limited. Most of such reports speak approvingly of the mulches for temporary fixation of the moving sands. The disadvantage of these mulches is their impermeability to water and increasing the temperature maxima of the buried sand.Despite these shortcomings, these materials, especially the semi permeable emulsified types, are unsurpassed in temporary fixation of extensive areas covered with the moving dunes. Environmental impacts of such activities, however, should be contemplated beforehand.

Sanguisorba minor is one of the important species in plant composition of mountainous rangelands. Its cultivation in Gorgan had good results. For this reason it was necessary to study the cultivation problems of this species. Determination of seed rates and planting spaces for yielding the maximum forage yield was the main objective of this study. This research was conducted in Chalaki Station which receives about 450-600 mm rainfall annually. A split plot design with 4 replications applied. The treatments were seed rates (10,15,20 kg/ha) and planting spaces(40,60,75,100 cm). Results showed that 40 cm planting space and 15 kg seed rate produced maximum forage yield (5250 kg/ha ). The treatments had different results in 4 years of study period.

Water spreading influences on quantitative and qualitative of vegetation cover in Varamin were evaluated by measuring plant productivity. These factors were measured on water spreading area by 50 sample plots, and 20 plots on control area. Dimensions of plots were 1x1 meter. Three plant species were sampled and determined crude protein, ash, calcium, and phosphorus. Plant productivity didn't indicate significant deference a 95% confidence interval on water spreading area and control area in 2001 and 2003 years. Also, plant productivity ANOVA on water spreading areas has not been had significant a 95% confidence interval. There wasn't deference between crude protein, ash, calcium and phosphorus on water spreading area and control area. There were flooded 711078 in 1998, zero in 1999, 393549 in 2000, 2523694 in 2001, 2628549 in 2002,960606 cubic meters in 2003 year. In addition enough flood has not spread on water spreading area, so has not varied vegetation cover until now.