Desert
Year:2000 | Volume:5 | Issue:2|Papers Count:6

Salty clayey lands that are dominated sebkha are sensitive to wind erosion. There lands are scattered in desert lands and in Iranian central palteus. Biological methods for their control are impossible because chemical and Physical characterization soils are unfavorable. However, gravel mulch plan was used. This paint is natural in the desert lands in pavement regions namely Hamada. This research was made with four gravelly coverage density, 0%, 25%, 50%, and 70% on three groups of sensitive lands to wind erosion in Yazd - Ardekan plain. Kind of selected gravels were in sizes such as almond, sand and stone that were provided form mines. Winds with determined speed were produced by wind erosion meter instrument that is kind of wind tunnel. Much scattered lands with different densities are affected with wind in 10 ms^-1 speed and 20cm height (egual to 76 Km hr^-1 with 10 m height) for 30 minutes. Gathered sediments in determined area (30cm * 100cm) was compared with control units (bare and without mulch). Obtained data were surveyed in the basis of factorial expen.i1ent as CDR with Mstatc programme. Results show significant differences in all of treatments because of effect of mulch due to reduction of wind erosion. There isn't significant difference between almonds gravely mulch and oversize kind as over-size mulches are cheap and available, they are used in applied plans. Comparison between effect of mulch densities between 50% and 75% showed that there was not significant difference and maximum difference was between mentioned densities and 25% and 0% (control). According to research results, oversize gravels (small stones) in sand mines with 50% density are suggested as the most suitable gravel mulch in lands sensitive to wind erosion. Production of monotonous coverage and survey of marginal effects are cases that in different research plans must be studied.

In this study phonology of Stipagrotis plumosa, Astragals squarrosus, Smimovia iranica and Zygphyllum eichwaldii in different stages of vegetion growth, flowering and fallig seeds were investigated in each stage, the effect of minimum and maximum air and soil surface temperature were considered. The study was carried out in the sand dunes of Band-e-Rig of Kashan in the centeral part of Iran. These species are important in terms of wind erosion control and livestock feeding in arid areas. The results have showen that during the growth stages air temporar, ranged in stipaqrostis plumosa from -2.2°C to 41.5°C, in Astragalus squarrosus from -1.8°C to 42°C, in Smirnovia iranica from -1.8°C to 48°C, in Zygophyllum eichwaldii from -2.2°C to 41.5°C and soil temperature varird in Stipagrostis plumosa -3°C to 52°C, in Astragalus squarrosus from 4°C to 48°C, in Smimovia iranica from 1°C to 80°C and Zygophyllum eichwaldii from -4°C to 48°C.

In order to evaluate the potentiality of satellite data in classification of Saline Soils a thematic mapper subscene of Hoze-Soltan area in Qom province, Iran dated september 1991 was analysed. The satellite image was evaluated qualitatively. Geometric registration of image data was implemented using ground control points which were taken with DGPS. The RMS error was calculated to be about a half-pixel (0.55m). Different image enhancement techniques such as Band-Ratioing and PCA had been determined. 52 samples were taken random and systematically from topsoil and subsoiL The salinity parameters such as Electrical Conductivity (Ec) pH and soil texture of the soil samples were determined in the labratory. By specifying sample site on the geocoded satellite image, digital number (DN) relevant to the samples were extracted. Relationship between extracted DN and measured soil parameters were studied. According to the results, correlation coefficient for TM4 and TM3/TM4 was higher than other origin and synthetic bands. Although, the highest obtained coefficient (r=0.54) is significant at the 1% level, but it is not sufficient in order to use in classification of saline soils.

A laboratory experiment was conducted to study the effects of calcium ion (0, 10 and 20 me/lit) on germination and seeding growth of lentil (Lens culinaris M., var. Ghaxvin) under deferent levels of sodium chloride salinity (5, 70, 140 and 210 me/lit). The results showed that seed germination. Radicle and plumule lengths decreased with increasing levels of sodium chloride concentrations. Addition of 10 me/lit calcium in the growth media increased both seed germination percentage and lengths of radicle and plumule. When calcium concentration in the growth media irrespective of salt concentration was raised to 10 me/lit, percent germination, radicle and plumule lengths were increased by 50, 111 and 124 percent, respectively. The results also showed that when Na+: Ca2+ ratio in the growth media was 14: 1, the delitereous effects of sodium chloride on lentil seed germination and seedling growth was reduce. The results indicated that, to some extent, calcium ion in the growth media offset the harmful effects of sodium on both germination and lengths of radicle and plumule of lentill.

The above mentioned project was executed in South of Semnan (Koh Sorkh) Formation of koh Sorkh is Upper Red Formation (U.R.F) Including, Mad, Anhydrite, Shale and Evaporate, including; Halit, Gypsum, Anhydrite. Lithology and geomorphological studies showed that Pseudokarst phenomenons occur in U.P.R and Salt Domes. Geomorphlogical studies showed that Pseudokarst landforms are as follow: 1- surface landforms or landforms resulted from surface weathering includes, rain pit, solution flutes.2- Landforms resulted form Water Erosion includes badland and natural bridges.3- Composition of surface and underground forms includes, landforms resulted from Piping erosion.Studies and field observation showed that the most interesting Pseudokarst phenomenon is Piping Erosion. This phenomenon in studied area is formed in different forms and dimension. According to geomorphological studies, this landform is affected by washing out of particles, Solution, available relief, Texture and Bedrock of formation, soluble salt content, hydraulic gradient, rates of surface runoff and denudation.

One of the main problem in hydrological studies of low -water flow (drought) and high - water flow periods is absence or deficiency of hydrometric statistics. This problem is due to high expenses of establishment of hydrological stations, difficulty in maintenance of stations and the fact that not all drainage basins are accessible. In this research after investigation of hydological stations present in salt Lake Drainage Basin. 19 stations which have the best stations in the view of length of statistical periods and the other properties, were chosen and seven day low flows (minimum flows). Q %90 and maximum discharges were extracted. After reconstruction and extension of statistics, done by HYFA computer program, the above - mentioned factors were determined for 2, 5, 10, 25 and 50 year return periods. For determining analogous drainage basins and homogeneous groups, 14 morphometric, climatic and geologic parameters of selected drainage basins were extracted and important and independent parameters were chosen by analysis to factors. Then by using chosen parameters, analogous drainage basins were determined by two methods of numerical homogenization (such as cluster analysis) and non - numerical homogenization (such as Andro curves). Then the minimum and maximum flows for each station were estimated by area - ratio between analogous drainage basins. At the end, the efficiency of graphic and numerical methods for determinations of analogous regions and also the efficiency of transfer method of indices in estimation of minimum and maximum flows were discussed.