Desert
Volume:15 Issue: 1, Winter - Spring 2010

Abstract The objective of current research is to investigate distribution patterns of vegetation types and its relation with environmental factors in southern margin of Haj Aligholi Kavir of Damghan. Three vegetation types including Halecnemum strobilaceum, Sedlitzia rosmarinus and Artemisia sieberi were studied in marginal arid regions and uplands of the study area. Firstly, geographic location of vegetation types was determined using GPS. Then the boundary of the region was delineated on the topographic map in scale 1:50000. Elevation, slope and aspect of vegetation types were determined as well. Ten plots were established in the field based on randomized – systematic approach. The area of each plot was determined according to the kind of plant species and distribution of plants. Floristic list, canopy cover and average percent of species canopy cover were determined in each plot. Finally, five soil samples were taken in each vegetation type. The characteristics of soil samples including texture, EC, pH, %CaCO3, %CaSO4, %OM, SAR and ESP were measured too. ANOVA and Duncan''s test were used to analyze the collected data. The result of analysis of variance showed that F test of all studied characteristics except %CaCO3, %CaSO4, %OM and elevation is significant in %1. The results of Duncan''s test showed that soil texture, EC, SAR, ESP and pH of Halecnemum strobilaceum type is significantly different from two other types. Also, SAR, ESP and slope in habitat of Artemisia sieberi and Sedlitzia rosmarinus types were significantly different

A watershed management program is usually based on the results of watershed modeling. Accurate modeling results are decided by the appropriate parameters and input data. Precipitation is the most important input for watershed modeling. Precipitation characteristics usually exhibit significant spatial variation, even within small watersheds. Therefore, properly describing the spatial variation of precipitation is essential for predicting the water movement in a watershed. This study is concerned with mapping annual precipitation in Jam and Riz watershed of Iran, from sparse point data using Inverse Distance Weighting (IDW) method. The objective in the optimization process is to minimize the estimated error of precipitation. Thus the performance of each interpolation was assessed through examination of mapped estimates of elevation. The results show that the estimated error is usually reduced by this method. Particularly, when optimized exponent in IDW method was selected for digital elevation model which, is secondary variable for the annual average precipitation gradient equation. It was conclude that IDW3 with the best conditions and lowest mean standard error provides the most accurate estimates of precipitation

Abstract One basic method of improving rangelands in a country is the use of native as well as exotic species of plants adaptable. Among the but introduced species, Atriplex canescens has been introduced in many rangelands, but it is important and necessary to consider it’s effects on native species. In the current study the effect of chemical competition (allelopathy) of Atriplex canescens on germination of Salsola rigida has been taken into account. Salsola rigida is known as a native species of good quality traits in arid and semi-arid rangelands. In this survey 10% weight/volume (w/v) of extract from leaves and fruits of A. canescens was prepared and 25%, 50%, 75% and 100% concentrations were obtained through addition of distilled water. Distilled water was used as control treatment. Altogether five treatments of four replicates, based on a completely randomized design (CRD) were studied germination during 8 days. Different groups of treatments were categorized through Duncan’s new multiple range test. The results indicated that the available material in shoots of Atriplex canescens (fruits and leaves) exhibited allelopathic effect on germination of Salsola rigida. The highest percentage of germination was obtained from control while the lowest from the 100% treatment. In fact after exceeding of 25% concentration, germination reached its lowest percentage due to Atriplex effects.

Abstract A basic aim of low energy architecture is to create a thermally comfortable internal environment for building occupants whilst consuming the least possible amount of energy. In desert countries this aim is more difficult to achieve since high ambient air temperatures create a barrier to comfort. Traditional building types of these countries, such as courtyard building, have evolved to try and help people to adapt to a state of thermal comfort under these adverse conditions. Their indigenous people were known to have operated sophisticated irrigation systems for their living, and to have adapted to an appreciation of the nature and dynamics of physical systems. This paper looks at the desert climate and its effects on architectural design and the significance of the living conditions in such environments. A best solution for building design, just in terms of building’s form, could be made. The implication of the conclusion on architectural design gives useful guidelines in designing naturally ventilated buildings with internal courtyards in desert condition.

Abstract The main objective in this article is to study the issue of development and lasting competitiveness and to study its dimensions and also to acquainted with its related components and how to achieve it. In fact, to get acquainted with competitiveness is as a development that would prevent imposition of cultural, Economical, and social and/or environment damages on future generations. In this article a reference has been made to roles and requirements and correct management of resources in safeguarding and protecting environment and aims of technology strategy in lasting and permanent competitiveness has been discussed and analyzed. Finally, strategic approaches conclusion and also its related proposals have been delivered and explained. Since the resources are limited and the needs are increasing in the developing countries, writing the required strategy as a framework for optimized allotting of the resources is necessary for all three types of development. This is a fact that the developing countries demand new needs for the people of these societies due to the weak technology and because the public media demonstrate the new life styles on the one hand and they confront dangerous and critical situations on the other hand. On the one hand the gap between these countries with the developed countries is increasing and on the other hand their facilities are decreasing due to various political, social and economical crises and the shortcoming of the initial resources and energy for growth and development. Therefore, there will remain little opportunities for compensating the weaknesses.

Abstract Flood causes great and uncompressible damage to people’s life and properties as well as environment each year in Iran. This research was carried out at the west section of Jazmurian basin that placed in the southeast of Iran. In this research physical characteristics such as area (A), perimeter (Pr), average elevation of basin (av.e), average slope (av.s), gravelious coefficient (G), length of main stream(L), pure slope of main stream(Pur), Lc, Tc and Tl for independent variables and hydrograph component such as Qp, Q25, Q50, Q75, Tp, T25, T50, T75 and Tb for dependent variables were used. For this the data of 12 hydrometric stations were used. Normality test was done by kolmograph- Smironov. After that using two and multiple variables regression analysis and with the use of modeling, the relation between dependent and independent variables were defined. The evaluation of hydrologic model behavior and Performance is commonly made and reported through comparisons of simulated and observed variables. Frequently, Comparisons are made between simulated and measured stream flow at the catchments outlet. Significant models are included the models that have correlation coefficient bigger than 0.325 at 1 percentage level and bigger than 0.250 at 5 percentage levels. We used three criteria such as RMSE, RE and CE for selecting the ultimate models. These models have less RMSE and RE and more CE. The results approve that with the use of physical characteristics of the basin we can determine the synthetic hydrograph. The results also show that the two- variable models have higher efficiency in estimating the discharge variables of the simulated hydrographs

Abstract Over the last fifty years, most of the semi-arid rangeland in Iran has been converted to cropland without an equivalent reduction in grazing animals. This shift has led to heavy grazing pressure on rangeland vegetation. The present study has been conducted in Sisab Research Station in the North Khorasan Province to evaluate effects of long-term grazing exclosures on biodiversity of range plants. The study was initiated in May 2008 using three transects within the exclosure and another three transects near exclosure, each with 100m length in the vicinity of exclosure has been established to determine differences in plant composition between areas that have not been grazed in 22 years with neighboring grazed plant communities. The sampling method was randomized systematic one comprised of 10 plots, each of 1m2 in area. A total of 53 plant species were identified in the study area with the ungrazed plots containing 18 plants more than the grazed plots. The major species were Festuca ovina, Centurea depressa, Stachys turkamanica, Stipa barbata, Astragalus sp and Phelomis cancellata. Grazing impacts on forbs were more pronounced than for grasses and shrubs. Based on Jaccard’s index, there was only a 45% similarity of plant species between the two treatments. Our study led to four generalizations about the current grazing regime and long-term exclosures in the semi-arid rangeland around the study area: (1) exclosures will increase species richness, (2) heavy grazing may have removed some plant species, (3) complete protection from grazing for a prolonged period of time after a long history of grazing disturbance may not lead to an increase in desirable plant species with a concomitant improvement in range condition, and (4) research needs to be conducted to determine how these rangelands can be improved.

Abstract The impact of rainfall and light interception by litter on maintenance of surface soil water content is determined in an arid rangeland in Khabr National Park in south-east of Iran. Litter weight sampling is done by 90 square plots, each 1 m2, that are randomly placed within site. After determining the intensity of a typical storm of the region (20 mm/h), the rainfall duration required to saturate the litter from dry-weight to constant-weight is determined from the litter wetting curve. To plot the wetting curve, an outdoor rainfall simulator is used to wet the litter. Then drying curve of litter moisture content is determined from obtained field data with four replications. For measuring soil water content, three treatments are tested i.e. bare soil, soil with wetted litter and soil with dry litter. Average of the measured interception loss of four samples was 0.64% of this specific simulated rainfall (5.2 mm). This study clearly showed that rangeland litter decrease evaporation of the soil water content and light interception by litter have more important role in decreasing evaporation from the soil water content than the rainfall interception by litter.

Abstract Nickel is a heavy metal distributed ubiquitously in nature. It accumulates in soil as a result of human activities, including mining and industries development. It may be poisonous to plants, humans, animals and microorganisms. The present study was implemented as a factorial experiment with a Randomized Complete Block Design (RCBD), of three replications in calcareous soils of Karaj and in greenhouse conditions for detection of the effect of nickel polluted soil, Ni125, Ni250, Ni500, Ni1000 (mgkg?1) in comparison with control (Ni0). The inoculant of resistant native bacteria to nickel in three levels, of: control (B0), Bacillus mycoides M1(B1), Micrococcus roseus M2 (B2) were examine on nickel phytoremediation in alfalfa (Medicago sativa L.). Results demonstrated that by increasing the polluted nickel concentration in soil, its absorption by the alfalfa have increased significantly (P<0.05). The plant growth and biomass accumulation severely decreased by increasing nickel concentration in soil. Application of native inoculant (B1 and B2) resistant to nickel significant increased the nickel concentration in plant shoot compared to control, and also increased the concentration of iron, zinc, copper and manganese in plant shoots. The highest nickel uptake occurred with B2 inoculant and during the second cutting of the plant growth, which was 350 µgPot?1