نشریه خشک بوم
سال نهم شماره 1 (بهار و تابستان 1398)

Recognition of source areas of sand dunes is very important in wind erosion control projects. Due to the difficulties in application of traditional methods in recognition and determination of the sediment source apportionment, fingerprinting method (source identification), as an alternative and suitable method has been considered in several studies. This method, determines the source areas of sediment using physical and chemical characteristics of sediments, rocks and soils of different sources. In the current research, sediment production share of these sources is determined through the use of appropriate combination of separation properties of sediment. Furthermore, using appropriate combination of geochemical elements capable of isolating different land uses, the contribution of each land use to the production of sand dunes was determined in Gachin, Iran. Initially, 28 samples were taken from the possible sources of sediment and sand dunes, and then statistically investigated through analysis of variance and Kruskal-Wallis to identify the optimal combination of tracing tracers. The results revealed that of the all tracers, P, Na and Mg were the optimal combination for differentiating land uses in the region. Outputs of Composite Multivariate method showed that the percentage contribution of pasture land, agricultural land, forest planting, and bare land appeared to be 31/25, 2/85, 2/85 and 63/05, respectively. The relative error of the hybrid model to estimate the contribution of different applications in the production of sediment was equal to 7/65 % with a correlation coefficient of 92/35. In conclusion, considering the relative error and capabilities of fingerprinting technique, it has been demonstrated that this technique has an acceptable performance for the sediment source apportionment.

Climatic conditions of each region are the primary factors affecting the formation of settlements. Precipitation is one of the most important climatic parameters that contributing in changes in vegetation, especially in arid and semi-arid ecosystems. This study aimed to investigate the vegetation and precipitation changes using remote sensing data. The vegetation index images captured by X TERRA / MODIS between 2001 and 2013 with 8-day interval in May and June months were used as Vegetation Condition Index (VCI). Consequently, VCI as an index was calculated from the annual average of the two months. To evaluate precipitation data, we used data from 28 meteorological stations. The linear correlation between height and precipitation was used to obtain line equation at each station using DEM (Digital Elevation Model) maps to prepare precipitation maps for each year. The VCI images were normalized between zero and one and were grouped into four classes. The area of each class was then calculated in 2001 and 2013, followed by statistical analysis (i.e. chi-square test) . The results showed that both indices were significant at 95% with Sig = 0.000. The VCI index decreases when the precipitation is low, while it shows an increasing trend where the precipitation is medium to high, which in turn approves the vegetation dynamics.

The purpose of this study was to compare the efficiency of two models of IMDPA and ESAs in assessing the intensity of desertification in the drylands of southern Khorasan Razavi province and management based on the best-performed model. For each geomorphological unit, initial data was first collected, and Criteria and indices of the models according to regional conditions, were then scored and intensity of desertification calculated. This was then followed by assessing the risk of desertification from the combination of hazard intensity, elements at risk and environmental vulnerability data. Maps were then verified and validated against ground control points, using Chi-square test and Kappa index. The results showed that based on the IMDPA model, the most intensified area of desertification in the region with 54.7% frequency was the highest area with severe desertification intensity with distribution with the climate and vegetation criteria appeared to be the most controlling factors. In the ESAs, desertification intensity was classified into three classes, with the highest area of the second-class critical class with a frequency distribution of 79%, and the climate and wind erosion rates had the highest impact. This emphasizes that the impact of natural factors on the desertification process in this region. Therefore, based on field studies, expert opinion and Kappa index of 0.897, the ESAs model was selected as the most appropriate model. Risk assessment results show that more than 51.5% of the environmental elements, located mainly in the central and southern parts of the region, are at moderate to very severe risk of desertification, which can generate annual damages of IRR 7.6 billion. Therefore, the implementation of suitable programs for combating desertification in the studied area can reduce this damage and its costs.

The increasing of environmental stresses concerned identification of plants that have high performance in both normal and stress conditions. Ideal genotypes have high performance in normal conditions and show the fewest changes under stress. Euphrates poplar (Populus euphratica Olive.) is the unique poplar species in desert areas with high tolerance against some environmental stress, including salinity. This research was carried out with the objective of investigating the effects of different salinity levels on the yield of different ecotypes and introducing the best ecotype. In this study cuttings were taken from 12 ecotypes of Euphrates poplar in Iran and treated by salinity levels of 0, 75, 150, 225 and 300 mM NaCl. The research was conducted in Two-way Factorial arrangement on a CRD design with three replications. The yield and productivity index (diameter and height growth, biomass production; leaf, stem and root biomass (dry weight) and total biomass) showed significant difference (p<0.01%) in salt levels treatments and ecotypes. The indices such as MP, GMP, HarM, TOL, SSI and STI were evaluated for each ecotype and salt treatments. The Hamidyeh ecotype was located higher than others in Duncan’s Multiple Range Test; and 75 mM NaCl was located higher than other treatments. In fact, the salinity increases growth rates and Euphrates poplar showed some halophytes’ characteristics. There was a high positive correlation among yield and indices GMP, GMP and SSI; while there was a negative correlation among yield and indices HarM and TOL. There was no correlation between yield and STI (p<0.05). Therefore, SSI is a suitable indicator of stress tolerance. The cluster analysis divided the ecotypes into four groups: Jolfa, Manjil, Sarakhs, Gonbad, Dezful and Mahallat in the first group, Hamidieh and Masoumieh in the second group, Maranjab and Gilvan in the third group, and finally, Marand and Mahanshan in the fourth group.

Dust storm and its mitigation require in-depth knowledge of prevailing parameters and their interaction. Accordingly, study of dust storm motion and its deposition have special significance. Among the dust storm studying methods, simulation is important because of its lower cost and independency on experiment or satellite. The goal of this study was to simulate the motion and deposition of clay dust storm particles with size of 0.001 to 200 micron affected by wind speed of 1, 3, 10 and 20 m.s-1 on a smooth land and hypothetic obstacles with a height of 6 and 12 m. Gambit and Fluent are used for creating the simulation environment and solving the continuity and Navier-Stokes equations coupled with turbulence intensities equations. According to the results, wind speed is a negative factor for dust storm particle deposition on earth and obstacle surfaces and it is independent of the obstacle height. Therefore, particles under one micron remain primarily in the air and they deposit lower than 10 percent, so they can transfer to farther distances. The larger the particles, the more efficient the gravitational mechanism in their deposition phenomena; such a way that the deposition calculated more than 30 percent for particles larger than 100 microns. At the same wind speed and particle size, the 12m obstacle postpones the deposition because of the separation of the flow from the surface and turbulence and it also decreases the deposition of particles under micron to lower than 1 percent. The deposition of these particles doesn’t vary with wind speed but the one for particles larger than 10 micron is inversely proportional with wind speed.

General circulation models (GCMs) have been used to predict future climate change by climate agencies. GCMs outputs as local interfaces have larger spatial resolution than the simulated variables. In the present study, the Statistical Downscaling Model (SDSM) was applied to estimate the variability of rainfall and temperature in Kashan and Khur and Biabank synoptic stations in Isfahan Province, based on climate change scenario downscaled from HadCM3 Model. For this reason, firstly, the variation of mean temperature and rainfall for base period was investigated under A2 scenario of HadCM3 model using the daily long-term data from the stations.The estimation and prediction of future periods (2039-2010), (2069-2040) and (2099-2070) was then carried out. The results showed that in both stations, simulated temperature and rainfall values had a close consistence with observed values, but the performance of downscaling process in rainfall prediction was less than temperature during calibration and validation periods. Results showed that for Kashan station the mean temperature will change by 0.42, 1.08 and 2.16◦C during (2010-2039), (2040-2069) and (2070-2099) for A2 scenario as compared to the baseline period (1987-1987). The results also showed a decrease in average temperatures in January, February, March, September and December, and an increase in other months. The results of Khur and Biabank station also showed that temperature will continuously increase in the region. Furthermore, the average annual rainfall increases 1.38 mm under scenario A2 during the prediction period (2070-2099) compared to the observation period.

Calligonum polygonoides is one of the shrub plants resisting to drought climate. This desert plant has an important role improving soil structure and organic matter, sand stability and windbreak in Sistan and Baluchistan Region, Iran. In this research, dispersion of C. polygonoides in three regions of Sistan and balochestan (Zahak, Tahlab and Jazmurian) was evaluated by quadrat-based methods (Taylor, Iwao, Morisita, K and variance to mean ratio) and distance-based methods (T-square, Hopkins, Holgate, Johnson, Zimmer and Pielou) using a simple random sampling campaign. That way four transects (each one 100 meters) was placed in three areas of 5000 m2. The result of this research showed that C. polygonoides is randomly distributed in Sistan and Balochestan. Taylor and Morisita of the quadrate-based methods and Pielou and T-square indicators of distance-based methods appeared to be the most appropriate techniques for determination of the plant the dispersion in conclusion, result showed that quadrat-based methods have more accuracy with same performance compared to distance-based methods.

The herbicidal properties of some plants species can be exploited successfully as a tool to reduce the herbicide application. Wild plant species, including medicinal herbs, usually contain much higher levels of chemicals compounds than the cultivated crops; therefore in the present study, the effects of drought stress on inhibitory properties of Esfand on purple weed in both laboratory and greenhouse conditions were investigated. Factorial design experiment in a completely randomized design with four replications was used. In laboratory conditions, the factors studied included the concentration of extract in four levels (0, 0.4, 0.8 and 1.2%), irrigation treatment on the mother's base of the plant manufacturer in Esfand was irrigated at two levels (native rootstock and Irrigation was not done) and the type of extracted organ was considered in two levels (shoot and root). In greenhouse conditions, instead of extract of Esfand plant residual (0, 4, 8 and 12 g) in 1000 g of soil was used. The results showed that in both greenhouse and laboratory conditions, with increasing concentrations  and amounts of shoot and root powder, the inhibitory effect was significantly increased on the most traits measured in the purple species (p

Wind speed is one of the most complex meteorological parameters in a specific region Furthermore, climate behavior in an area is influenced temporally in short and long terms. In the present study, Mann-Kendall and Petit nonparametric tests were applied to analyze the trend of monthly and annually wind speed data series in four synoptic stations of Lake Urmia (Tabriz, Urmia stations with 50 years, Mahabad and Sahand with 28 years). The results of the aforementioned tests, based on annual and montly scales, showed that the average wind speed at all stations has an increasing trend at 99% confidence level. However, the concerned years were not appeared to be quite identical in all stations. These changes occurred at Mahabad station in 2000 and at other stations in 1995. Also, the wind speed increased at Mahabad station in winter and at other stations in spring and summer.

The earth landscape is always changing due to human activities and natural phenomena. Therefore, in order to optimize the management of the natural areas, knowledge of the trend and extent of land cover / land use changes is considered necessary, and the estimation of these changes is of great importance. Reviewing these changes through satellite images and predicting and evaluating their potential through modeling can help environmental planners and natural resource managers to make more informed decisions. In the present study, quantitative detection and evaluation of changes in vegetation was performed in the areas with combat desertification projects, Shahdad and Bam in Kerman province and Garmsar in Semnan province, during a 30-year period within 1987, 2002 and 2017. The NDVI vegetation index and land use maps were produced using the ETM + TM and OLI satellite images in the three corresponding periods for the vegetation lands/non-vegetation lands, and agricultural lands. The Kappa coefficient of 0.83 to 0.86, 0.91 to 0.92, and 0.94 to 0.95 was calculated for 1987, 2002, and 2017, respectively, and the total accuracy was between 88 % and 97 %. After providing the land use maps in different years, the monitoring of land use changes was investigated using the change detection methods. According to the trend of changes during the studied periods, our results showed that the vegetation lands in these three areas had an increasing trend, and the non-vegetation lands were turned to vegetation lands over time. Moreover, an increasing trend was found for the agricultural lands during these three periods. Finally, the cost-effectiveness of projects implemented in the studied areas was calculated and evaluated.