نشریه مهندسی اکوسیستم بیابان
پیاپی 8 (پاییز 1394)

Detecting the spatial distribution of dust storms in the deposition regions is an essential step for managing this natural and human-induced crisis. This study aimed to investigate the performance of the Normalized Differences Dust Index (NDDI) applied to MODIS data (4/7/2009) for detection of dust storms in the Khuzestan Province. The extracted NDDI map was classified by value pixel in six classes including very severe، severe، medium، low، very low and non-affected and their accuracy were assessed using visibility data recorded at meteorological stations and PM10 data at two air pollution stations in Ahvaz town. According to the results 64814 out of 94579 pixels of the study area were between threshold values between -0. 8 – 0. 9 which covers 68. 59 percent of the region. In spite of the good performance of NDDI in the previous studies، results of mapping dust intensity in this study in comparison with visibility and air pollution data indicated that this index underestimates the concentration of dust in the Khuzestan Province. It seems that this low performance of NDDI relates to land use/cover and topographical differences and also chemical characteristics of dust minerals in the study area.

Selecting appropriate alternatives considering effective criteria are useful to decision making for arid areas managers. The present study tries to present the main desertification strategies based on quantitative method. Other methods of the assessment of desertification strategies do not study the dependency and the relationship between criteria and alternatives in decision-making level. These methods only rank criteria and alternatives with the hierarchical structure, from up to down, and specify their weights. But complex internal relations between criteria and alternatives and their effects to achieve the ultimate goal requires a network analyzer. So in this study network analysis process (ANP) model were used. For modeling and analysis the data, internal and external dependencies matrix between alternatives and criteria were calculated. Alternatives were weighted using the designed network model and the main alternatives were evaluated and prioritized. The results showed that among 16 criteria and 40 final alternative surveyed, the results showed that the alternative of vegetation cover development and reclamation (A23) with general rating (Di= 0.2249) is the most important alternative in combating desertification process in the study area, and alternatives of prevention of unsuitable land use changes (A18) and modification of ground water harvesting (A31) were in the next priority with general rating of 0.2245 and 0.1852, respectively. Therefore, it was suggested that the results and ranking obtained should be considered in controlling and reducing the effects of desertification and rehabilitating degraded lands plans.

World reserves of petroleum are being consumed rapidly and expected to exhaust by the middle of this century. This realization has led to the introduction of various grades of ethanol supplemented fuel. However, ethanol demands met from sources used for food may cause food shortage. This necessitates exploiting saline lands to produce non-food ligno-cellulosic biomass which, may be converted into ethanol without compromising human food production. Halophytes which produce plenty of biomass using saline resources (water and soil) may be an important alternative especially in desert regions. In current study, Atriplex leucoclada and Suaeda vermiculata were collected from Fars, Hormozgan, Khozestan and Semnan provinces and ligno-cellulosic composition was investigated. According to the results, Atriplex leucoclada has the potential as bio-ethanol crops. It is a perennial species and resistant to salinity, with high growth rates to produce ligno-cellulosic biomass of good quality (25-29% cellulose, 22-25% hemi-cellulose, and less than 8 % lignin).

Soil physical and chemical properties are the most important factors affecting plant growth Considering variability of soil properties in different areas, investigation on their effects on the plant growth is important, therfore, in this study the contribution of soil factors affecting the unwanted and invasive species in Lashgardar region at Hamedan province was investigated. Sampling was performed by Systematic – randomize method in 4 key areas and totally 45 plots were established (The key areas were identified by field survey and each plot had 3m2 area). In each plot, the percent of canopy cover and density of studied species were measured and two soil samples were taken from depths of 0-10 and 10-30 cm. Soil factors including pH, EC, percentage of nitrogen, percentage of organic matter, and soil texture were determined in laboratory. Data analysis was performed using multiple regression analysis. The results demonstrated that only 32 percernt of vegetation changes occur because of soil properties and soil texture has the gratest effect between them.

This study was conducted to investigate the effect of magnetizing fresh and saline water and seed on Atriplex lentiformis seed germination. This study was done in 2011 at the Yasuj University Lab and the study followed completely randomized factorial design. The treatments were as follows: water factor at 5 levels (0, 2/5, 5, 7/5 and 10 KGauss) salinity at four levels (0, 100, 200, and 400 mM sodium chloride and calcium chloride with proportion of one-one), and two types of seed (with normal and magnetized seeds) with four replications. The results of variance analysis revealed that there was a significant difference at at 0/01 for most of properties and for seeding weight the significant difference was shown at 0/05 level. The results also indicated that magnetic field level of 7.5 K Gauss was the most effective on saline water and it increased the figures of measured parameters. It showed that salinity and magnetized seed mutual interaction effect had significant difference on germination speed, seeding weight, and seed vigor properties. Among magnetized seed treatments, 7/5 K Gauss had a better performance in comparison with other treatments. There were significant differences among mutual interaction of water and magnetized seed of Atriplex lentiformis at 0/01 level in most studied properties. In general, it can be concluded that treatment of magnetized at 7/5 K Gauss is the most effective treatment in terms of effect on measured parameters.

Land degradation in arid and semi-arid regions caused by climate change and human activities makes it more susceptible to desertification. The aim of this research is assessing the intensity of desertification in Roudab plain of Sabzevar city using IMDPA model. So two criteria of climate and water as the main criteria affecting desertification process were considered based on field observations and regional conditions and scoring the indicators of these two criteria was accomplished according to their effects on desertification intensity and the model tables. Then integrating maps of indices related to each criterion by geometric mean method, desertification intensity map of climate and water criteria was obtained and finally, desertification intensity map was provided by integrating two climate and water criteria maps. The results show that climate criteria with the score of 1.71 and the water criteria with the score of 2.60 are both in medium desertification class. The ultimate desertification intensity map of climate and water criteria indicated that 10.85% of the studied area falls within the low class, 48.27% in the severe medium class, 34.63% in the severe class and 6.25% in very severe desertification intensity class. To prevent desertification process, it is suggested using modern irrigation techniques to prevent of quantitative and qualitative of groundwater reduction.

One of the methods of biological sand dune stabilization and reclamation of desert, Planting resistant species in areas of bare and covered with dry conditions. One of the plants used for the purpose of is Atriplex canescens. Considering that the successful establishment of plants in arid regions is a prerequisite for the success of the restoration area and since the medium first is where the young seedlings in the field of natural encounters, Therefore, the effect of soil factors on the establishment of Atriplex canescens research in in two planted areas with Atriplex in Omrani Gharbi of Gonabad city and Chah Goji of Mahvelat city. Data Measurements of vegetation (Crown diameter, canopy volume, production&…) and soil parameters (EC، pH, Nitrogen, carbon, texture &…) in each region was evaluated by Minitab software with two-sample t-test. The results of this study showing, soil parameters, including increasing soil Saturation percentage, reducing soil reaction and increase the amount of carbon and nitrogen in furrow cultivation and low electrical conductivity in the hole is filled with sediments and fine-grained texture in two types of cultivation can improve the growth of Atriplex. As well as soil saintly does not effect on the viability of this plant.

Determining the allowable use of key species in rangelands of Iran is necessary to range management. Despite of the importance of the subject, little information is available in this regard. The aim of this study was to investigate the response of plants to harvest intensities in order to determine the allowable use of the key species of steppe rangelands. Two key species, Artemisia sieberi and Eurotia ceratoides, were studied in Nodushan rangelands of Yazd province in this research. Study was performed in an enclosure area of rangeland in Nadoushan which is known an important pole ranch of Yazd province. Four different harvesting intensities, 0, 25, 50, 75%, were implemented for 4 years in this study. The results showed the tangible effect of year on the production of the studied species.In case of E. ceratoides, different harvest intensities had significant effect on the production where the removal treatments of 0 and 25% were obviously different from those of 50 and 75%. Then the allowable use for the E. ceratoides was established 25%. No significant effect of harvesting on A. sieberi was determined in this study suggesting the A. sieberi species is resistant to pressure of grazing and intense harvesting, at least in short term. This characteristic may be a major reason for the undisputed presence of this species in desert, arid and semi-arid areas of the country.

The protection and improvement of natural resources especially for desert vegetation need a comprehensive recognition of natural resources and relationship on Soil characteristics. One of the most important species growing in sabzevar desert is Stipagrostis pennata and in the current research the relationship between the physicochemical properties of the soils and growth characteristics of the S. pennanta including density, canopy cover and amount elements of soil have been studied in the land. A random systematic design has been applied in 4 sites called A, B, C, and D within a distincthabitat of S. pennanta. Soil samples have been taken from 2 depths (0 - 30 cm) and 30-60 and prop Hon of clay, silt and sand content, amount of N, P, K, C, Na, Ca and Mg have been determined in a soil lab. The soil physico–chemical and plant growth data have been analyzed through statistical methods using the SPSS software. Further finding of this study show that the growth characteristics of S. pennanta such as density, canopy cover and forage production rarely depend on soil chemical properties but there is a statistically significant positive correlation between the canopy cover and amount of Ca. This has been shown by higher canopy cover in site B which has higher Ca..The results show that there is direct relationship between the amount of nitrogen and growth properties off of Stipagrostis pennata and other elements of the soil was not significant.

In order to evaluate and compare the yield of mixed and pure range land species, this research was carried out of semi-Arid of Gonbad Kavous. The plan was designed complete Blok with three replications in crop year of 2012-2013. The treatments were with 5 levels of monoculture planting pattern included, Festuca ovina L, Festuca arundinacea Schreb, Medicago scutellata L, Agropyron elongatum Analysis of variance showed that planting pattern in forage yield and seed yield have significant effects (1%) Results showed that the highest yield was in mixed cultures by 2018.01 kg/ha and lowest yield by 416.96 kg/ha. The highest seed yield was 969.34 kg/a for M. scutellata. Comparison of means treatment showed that maximum of dry matter digestibility was for M. scutellata and cultures treated by 64.45 percent and at least some of traits of pure treatments by 49.54 percent (A. elongatum). The highest percentage of water soluble carbohydrates from pure cultures treated with M. scutellata 13.8 percent and minimum value of A. elongatum with 6.07 percent. Maximum crude protein was for M. scutellata pure cultures treated by 20.55 percent and minimum attribute the F. ovina monoculture treated with 11.83 percent. Maximum crude fiber was for A. elongatum with 46.39 percent and minimum treatment was for mixed cultures with 37.32 percent. Comparison of means treatment showed that ash forage cropping patterns to pure cultures of F. arundinacea treated with 9.83 percent and at least some of the traits of pure cultivation treatments of M. scutellata with7.45 percent, Land equivalent ratio (dry matter basis) for the species equivalent of 1.18 of the LER> 1 indicates that the result has been a mixed culture is better than in pure culture.