نشریه مهندسی اکوسیستم بیابان
پیاپی 1 (زمستان 1391)

Drought is one of most important factors in desert ecosystems that affect plant growth. In this study some of drought parameters in Calligonumpolygonoideswere studied under control and irrigated conditions in natural condition. Results showed significant differences in water potential between control and irrigated conditions. Proline content in control with the amounts of 3. 1 mg /gfw was significantly higher than irrigated conditions. The highest amount of soluble sugar also found in the controls. These results showed Irrigation significantly decreased water potential (more positive)، proline and total soluble sugar in Calligonumpolygonoides. The amounts of K+ were significantly higher than Na. There are not significant differences in relative water contentbetween stands and in average it was about 32 percent. It is concluded that this speciesadapted to its own habitat and by accumulationof proline، K+ and total soluble sugars regulatesits osmotic potential.

Salinity is one of the main osmotic stresses on growth and production of plants in arid limit. The use of salt endurance species in the restoration and development rangelands, particularly in arid is very important.Given the importance of annual medics in the restoration and development rangeland and the low awareness level of understanding of this species to salinity, This study aimed to evaluate the endurance to salinity during germination were annual medics. Salinity at the germination stage for the creation of Sodium chloride (Nacl) and salinity (0 (control), 0/25, 0/5, 0/75, 1 and 1/25 MPa) was used. Components, including germination percentage, speed and uniformity of germination and seedling growth components, including the shoot and root Length, dry weight root and shoot And their ratio under salt stress was being investigated. The results showed that with increasing concentration of salt in the germination percentage, speed and uniformity germination shoot and root Length and dry weight decreased in both species. The significant differences in the percentage of germination, root and shoot dry weight in salinity were observed among species. In this study, the increased levels of salinity, germination percentage decreased with the decrease in the value of M. scutellata the control treatment to 1/25 MPa Nacl treatment was reduced by 99 percent. M. polymorpha reduction of 96% in comparison to the control was observed in 1.25 MPa. The results showed that the species M. polymorpha and M.scuteellata is more resistant to salinity at the germination stage.

Management and control of poisonous and allelopathic plant species are from the main priorities for restoration of range and desert ecosystems. In a glasshouse experiment, seeds of Agropyron desertorum, a perennial forage grass, were sown within the soil media containing different proportion of shoots (0, 5% and 20%) and root powder, or soil taken from the under canopy of harmal plant. Experiment was conducted in a completely randomized design with 6 treatments and four replications. Seed germination rate and speed, and seedling morphological growth parameters of Agropyron were measured. Under the canopy of harmal plant soil pH (8.13) and texture (sandy loam) was similar to those in open areas, however the electrical conductivity was higher under the canopy (627 vs. 215). A mixture of 20% shoot powder (seed and fruit)and rangeland soil, significantly reduced germination rate and speed, and all growth parameters of Agropyron. Root powder and understory soil treatments did not induced negative effects, they even increased shoot weight of the target plant.According to our results applying a surface root plow, before the flowering stage of harmal plant, may positively increase establishment of Agropyron in the field.

The effect of various concentrations of drought and salinity solutions on germination of two species known as Agropyron elongatum and Agropyron desertrum were investigated according to factorial design. This investigation contains three repetitions, nine drought levels (0,2,4,6,8,10,12,14,16), and seven salinity levels (0,2,4,8,16,33,64). 50 seeds of any species were cultivated in Petri dishes on filter papers inside the germinator during each repetition. Test results show that the maximum germination in drought potential of 2 MP in A.elongatum species has been about 62/70 percent and the maximum germination in salinity potential of 0, in A.desetrum species has been 100 percent. As a result, it can be said that, according to the overall results obtained from this study, the A.elongatum species are more resistant against salinity stress and drought stress,than other species.

In arid and semi-arid ecosystems shortage of surface water has led to a greater use of groundwater resources. Water table in groundwater due to climate and human intervention is always fluctuating. Assessing change groundwater resource in planning and sustainable management of water resources in each region has of great importance. In this study were investigated changes of water table in the plain aquifer Aspas. For this purpose monthly data of 30 well of groundwater observation to demonstrate groundwater fluctuations in statistics course (2002_2009) was used and using nonparametric tests Mann - Kendall and Spearman significant trend for monthly and annual time series were evaluated at a significance level of 95%. For each series, the slope of trend line was computed using Sen's Estimator method. The results showed that in all stations (except stations Pahlevani side drainage and riverside Hajiabad, Babai, kenas - sefli and kenas sefla) groundwater level has a negative trend. Mann - Kendall showed that nearly 83 percent of stations have negative significant trends. Investigate slope of trend line in the Aspas plain shows that water table declined 73.5 centimeter in each year.

Different types of time series analysis models are commonly used for predicting hydrological factors. In this study, the situation of Soleimanieh spring discharge in Kashan was investigated using various time series models and mean monthly flow during 11 year period. Then, spring discharge predicted using the best modals for future 9 years. In this research, the data were analyzed using 12 time series models including Autoregressive, Moving average, Autoregressive-composite moving average, seasonal and non-seasonal models such as Box and Jenkins. Finally, the results showed that the value of AIC is the lowest and model parameters don,t exceed of one in SARIMA (1, 1, 0) (1, 1, 1) [12] model. So, this model was selected to predict discharge data. Then, Komogorov-Smirnov test was used to investigate the normality situation of the predicted data. The obtained results showed that predicted data are normal. Therefore, according to the results, it can be conducted as the type of selected model is very important and it affects the accuracy of output response. Also, according to the uncertain nature of hydrological issues, time series models are one of the best methods in hydrological prediction.

In order to deal desertification phenomenon it is necessary to identify its producing and increases causes. For this purpose several studies conducted inside and outside the country that have been led to submit regional models.. Each of these models has different pattern and use different indicators which can lead to different results. In this study, Fakhrabad plain of Mehriz region by extent of over 39,370 hectares was selected. Whit emphasizing wind erosion criteria, that is the dominant process of desertification in the study area, the current status of desertification evaluated by IMDPA and MICD Iranian models and the results of two models ware compared. The results of this evaluation showed that in both IMDPA and MICD methods, the middle class of desertification has greatest area that is 88/3% and 81/4% respectively. Comparison of desertification scores and different classes of land use using regression comparison of standardized values revealed that correlation between the obtained scores is about 33% while this correlation between the severity classes of current desertification is 42%. Also comparison of similar values of the corresponding showed that classes of desertification in IMDPA model is less than MICD model which can be related to the different nature of models in using of the geometric and the arithmetic sum of the indices. It can be concluded that MICD model is suitable for large-scale (with more accuracy& the less area) and IMDPA model is more fitted for smaller scales (with more area, less accuracy) of capacity.