نشریه مهندسی اکوسیستم بیابان
پیاپی 2 (بهار 1392)

Sentence determine the stability mechanisms to stress in Agropyron trichophorum at test with four different levels of osmotic potentials resulted from PEG 6000 including 0، -3، - and -9 executed in factorial and accidental manner with four interactions in hydroponic environment. Three genotypes of Agropyron trichophorum pasture types were used Arak (3755)، Semirom (3. 13)، and Faridan (4007) and four drought care (-3، -6 and -9 times distilled water). In this essay the sprouting percentage root length، shoot length، seedling length، root to shoot rate، seedling dry weight، seedling fresh weight، dry to fresh weight rate sprouting rate and seed health index were determined. The results showed that with increasing the drought stress، the root to shoot rate، seedling dry weight and dry to fresh weight rate factors increased and other attributes were reduced significantly. The best levels to assess the stability to drought were the -6 and -9 load potentials in all drought levels. In general، in tested genotypes، Arak (3755) genotype showed a better sprouting in under study potentials and had a meaningful preference to other genotypes. From assessed parameters، seedling length and seed index standard showed the most possible reaction to changing potential of water.

Seed priming is a common way to increase the speed and uniformity of germination under Under stress and non-stress conditions. The aim of this study was to investigate the effects of different levels of gibberellic, salicylic and ascorbic acid on improvement of germination indices of Zygophyllum atriplicoides under salt stress in laboratory Chemical stimulators used in this study include: 3 levels of gibberellic acid (125, 250 and 500 ppm), 3 levels of salicylic acid (100, 200 and 300 mg/l), 3 levels of salicylic acid (100, 200 and 300 mg/l) and 5 levels of salinity treatment (0, 0.2, 0.4, 0.8, 1.2, 1.6 m/l). Factorial test in the completely randomized design with four treatments was used to analyse data.. Results indicated that salt strees had inhibitive effect on germination and early seedling growth of Zygophyllum atriplicoides. Early seedling growth of Z. atriplicoides increased by pretreatment of seeds in chemical stimulators. Also tested the interaction of treatment showed that salinity levels and the greatest impact on increasing concentrations of gibberellic acid ppm250 germination characteristics of this plant. It can be concluded that seed priming seeds by gibberellic acid can cause resistance to the stage germination Z. atriplicoides salinity prone areas.

In order to evaluate effect of salinity on the germination and vegetative growth of grassland different salad burent Poterium sanguisorba two different experiments were conducted under laboratory and glasshouse conditions in summer 2010. In the first experiment six ecotypes (Semirom, Fereidonshahr, Tehran, Karsang, Damavand and farokhshahr) and four levels of salinity (0, 4, 8 and 12 dS m-1 of sodium chlorid under laboratory condition and in the second experiment four ecotypes of Semirom, Fereidonshahr, Tehran and Karsang and four levels of salinity (0, 4, 8 and 12 dS m-1 of sodium chlorid under greenhouse condition were carried out in factorial experiment with three replications. Traits of germination percentage, germination speed, length of radicle and plumule and seedling wet weight in the first experiment, protein, proline content, percent of Cl and Na above ground plant in the second experiment were measured. The results under laboratory condition, showed that with increased in salinity stress, percent of germination and speed germination, length of radicle and plumule and seedling dry weight were significantly decreased. Based on the greenhouse result, protein content significantly decreased, percent of Cl, Na and proline concentration significantly increased. In the germination stage and seedling stage, Ecotype of Tehran showed the maximum resistance to salinity stress.

Using seasonal floods is very important in arid and semi arid areas. Suspended sediments in the flood are caused changes in soil properties. The aim of this study is to investigate the soil chemical and physical properties affected by low quality floods irrigation. Sampling from three phases, in each phase three points (beginning, middle and end of the row) and in the depths of 30-0, 60-30 and 90-60cm were done. The results showed that the electrical conductivity, sodium, carbonate, potassium, gypsum and pH decreased but organic matter, phosphate and bicarbonate have increased in the most samples so that these changes are significant at the 5%. About soil texture, sand increased and clay has decreased in the depth of 0-30 cm so, soil structure has improved.

In this research study the daily and annually trends of precipitation in the central Kavir basin of Iran during 1951- 2007. The pixel data of daily precipitation from APHRODITE’s data base with a spatial resolution of 0.25˚ have been used. The Mann-Kendall (MK) nonparametric test has been used for determining the precipitation trend in this area. The trends have been tested in 3 levels 90%, 95% and 99%. This study illustrated that in confidence level of 99%, some area such as Loot Kavir had decreasing trend and some other area such as western and north heights of basin had rising trend of precipitation. But more than 80% of area doesn’t indicate any significant trend for annually precipitation in this 58 years period.

over-exploitation of groundwater resources in Chaharmahal va Bakhtiari province led to prohibition of some plains in this province. One of these plains is Sefiddasht aquifer. Artificial recharge can be an effective method to raise the groundwater table and resolve the groundwater crisis in this province. The most important step for successful accomplishment of artificial recharge is locating suitable areas for artificial recharge. In this research, Slope, surface infiltration, alluvial thickness, alluvial quality and land use parameters were analyzed, classified and map of every parameter prepared using GIS. To overlay the affective parameters in artificial recharge, there were used Boolean and Fuzzy models. Results showed that 1.43% and 9.97% of Sefiddasht aquifer are suitable for artificial recharge based on Boolean and Fuzzy models, respectively. Using land use layer, these values decreased to 0.92% and 4.12% based on Boolean and Fuzzy models, respectively. So, land use is a limitative parameter in Sefiddasht aquifer.

Timely and accurate change detection of earth surface features is extremely important for understanding relationships and interaction between human and natural phenomena in order to promote better decision making. Remote sensing data are primary sources extensively used for change detection in recent decades. In this study, images of Landsat (TM) 1985 and Landsat (ETM+) 2007 were analyzed using six change detection techniques in 55986 hectares in the region of Dehloran, Ilam province. Considered techniques of change detection were included: image differencing, principal components analysis differencing, NDVI differencing, canonical components analysis differencing, tasscap differencing and post-classification comparison. To determine threshold level, the statistical method has been applied which was achieved from thresholds changing. In this study, threshold level was set at ±1 standard deviation from the mean. After determining optimal threshold, areas having decreasing change, increasing change and no change was determined. Based on ground data and field visit and Google Earth, accuracy assessment of change detection techniques was carried out using overall accuracy and Kappa coefficient. According to the results, infrared differencing with overall accuracy of 90. 49 and Kappa coefficient of 91% showed the highest accuracy among applied change detection techniques and on the contrary, CCA2 differencing with overall accuracy 25. 48 and Kappa coefficient of 38% had lowest accuracy in land use/land cover change in study area.