Desert
Volume:11 Issue: 1, Winter-Spring 2006

The kind of land use and intensity of its change is considered as important desertification indices in different models. Land use change is one of the main anthropogenic factors in the desertification. The current research was carried out around Imam Khomeini airport, with an area of 32000 km2, in order to evaluate mentioned area''s land use changes effects during 1955-2003 on desertification. To study the changes, aerial photos of 1955 (1:55000) and 2003 (1:40000), in addition to IRS (Pan and LISS III) and ETM images of 2003 were used. Boundaries of different land uses were determined based on aerial photos and satellite images. In the next stage, boundaries were controlled in the field. Five kinds of land uses including agricultural land, abandoned agricultural lands, rangelands, industrial regions and complex, were distinguished in the study area. The extent of land uses areas, except to complex, has been changed during the 48 years. Rangeland has least change (1.5%), while 14% of agricultural areas have been changed into abandoned and industrial areas. This research showed that biomass has been decreased to 24355.6 ton during the last 48 years. This leads to the decrease of organic matter and decline of soil quality, which in turn causes a 32.9% increase of area regions with severe and very severe desertification intensities.

This study determined some spectral characteristics and relationship between Landsat spectral reflectance and soil surface color in the arid region of Iran (Kashan). The study carried out in the kashan area that covers 90000 ha. Consisting of mountain, hills and flood plain. Enhanced Thematic Mapper (ETM+) data collected on July 2002 were used for this research. The color composite images produced from ETM+7, ETM+4 and ETM+2 as red, green and blue respectively used in order to choose sample sites. The twelve sample sites were chosen based on resampled 3*3 pixels (90*90 m). In each site, the soil surface conditions and the munsell color of the soil surface were investigated in the field. Some physico-chemical properties of soil samples were also determined in the laboratory. Soil surface particle sizes were categorized into three classes: bare soil <2 mm in diameter, coarse fragment >2mm in diameter and vegetated soil. The results of this study indicates that munsell notation of hue, value and chroma are significantly correlated to the visible bands of Landsat (ETM+) data. From this study it may be concluded that visible reflectance of Landsat can be used to estimate soil color, if very precise result is not expected. More investigation are necessary in order to improve the obtained results.

The high quality and quantity seed production in old saxual shrubs are essential for regeneration and sustainable development of saxual forests in desert areas. The objective of this study was to determine the effects of different pruning height on saxual seed production. The study was carried out in an obviously wilted saxual forest located in Ashkezar desert in Yazd in 1994. The experiment was carried out in a split-plot design with 3 replications, with saxual density (250 and 125 shrubs/ha) as the main plots, and pruning height (10, 35, 70 cm, and a no-cut check) as the sub-plots. Pruning was done on autumn 1994. The forest was protected completely and the quality and quantity of seed production of marked shrubs were investigated on autumn 1999 and 2000. The 2-year results showed that saxual density did not have any significant effect on quality and quantity of saxual seed production (P<0.05). Pruning height had significant effect on percent seed longevity and net saxual seed production (P<0.05). Although no significant difference was observed in viable net seed production under different pruning height, the amount of viable net seed production at 35cm pruning height was 9.7 kg/ha, which seems adequate for saxual regeneration.

Laboratory studies were conducted to examine the effects of different concentrations of wild barley (Hordeum spontaneum Koch.) shoot and seed extracts on germination and seedling growth of wheat (Triticum aestivum L.) and wild barley. In this study, all wild barley shoot extract concentrations (with exception of lowest concentration) significantly reduced wheat seed germination after 7 days. Shoot extract concentrations of 60 and 120 g / L significantly reduced shoot and root lengths, shoot fresh and dry weights, and, root fresh and dry weights of wheat. Seed germination of wheat was not affected by intermediate wild barley seed extracts. Considerably, some extracts of wild barley seeds stimulated the germination and growth of wheat. Wild barley shoot and seed extracts at low level stimulated the growth of its own plant, however, its germination and seedling growth were inhibited at higher shoot extract concentrations. The results of this investigation show that wild barley shoot extracts exert more allelopathic effects on germination and growth of wheat and its own plant than those of seed extracts.

The majority of Iran’s area is covered by arid and semiarid climates. In these areas، wind causes more erosion compared to water. Therefore، determination of wind characteristics especially its velocity is very important. One of the simplest methods that can supply researchers with the origin of wind erosion in the shortest time is synthesizing sand rose model and interpretation of aerial photographs or satellite images. The main purpose of this research was to find the relationship of soil drift potential. Sand rose is a diagram that shows not only the direction of wind transportation but also the wind erosion potential. Using a formula، soil ablation potentials were determined for drawing sand rose. A computer program was used to simplify and speed up the computations and increase the accuracy. Two stations in Sistan – Balochestan province، namely Zabaol and Zahak were selected. These two stations are located on flat lands and are naturally faced with higher wind erosions. The two stations are faced with the 120 days winds of Sistan and have very high drift potential. The results of this study show a south- southeast direction of drift potential، which exactly matches the direction of 120 days Sistan winds. Interpretation of aerial photographs and satellite images confirmed the sand rose study results because most of sand dunes showed a south – southeast direction of wind. Considering the location of sand dunes result drift direction، and the distance that sand can be transported، the locations of sand ablation was identified to be waterways and pediments of Sistan and also agricultural lands around Zabaol and zahak.

Estimation of the magnitude and frequency of maximum instantaneous discharges and hydrographs are used for a variety of purposes, such as the design of bridges, culverts, flood-control structures; and the management and regulation of floodplains. Fuller (1914), developed a flood-frequency formula based on analysis of flood peaks in hundred of streams to provide simple methods of estimating maximum instantaneous discharges, and sought to link maximum instantaneous discharges having various average return periods to the mean of the maximum annual discharges with a factor calibrated for different catchments. The aim of this study is the evaluation of the mentioned method in order to estimate maximum instantaneous discharge and calibrating its considered coefficients in Kaal Shour Sabzevar region. Therefore, the collected data from 10 hydrometric stations in the region were used in analysis and regional coefficient was obtained 0.041 and regional inundation coefficient is from 0.88 to 2.23 in 5 to 200-year return periods. The results showed that thedischarge calculated by Fuller’s empirical formula is less than values calculated by statistical distributions.

There are many medicinal plants in Iran but there is lack of information about plants'' growth condition and application. Autecology is a science which can help us to investigate seasonal and morphological changes and condition that effect on plant distribution.In this study, the autecology and phonological studies for P.abrotanoides were done. At first, vegetation habitats of this plant were chosen in different regions of Kashan and six sites were selected. The observation and recording of plant in dormancy and activity periods were done every 15 and 7 days, respectively. All samples for measurement were selected randomly.This research revealed the temperature, air humidity and soil condition necessary for plant growth and development. During the two years of study, no pest or diseases were seen. This can be attributed to the existence of high amounts of plant essence.No ecological study has been done on this plant yet in Iran. Regarding to its vast distribution in Iran, other autecology studies are needed for comparing different habitats of this plant species.

Soil organic matters are considered as the animal and plant residues and active components of soils. The cultivation practices will cause the quick removal of organic matters in soils even in those which are not affected by erosion. This study was carried out to assess the level of soil humus in the pilot area, to investigate the positive or negative effect of humus level on soil and to introduce the most appropriate farming systemThe area is 12409 hectare located on the eastern north of Khodabandeh city. In order to identify land uses, aerial photos and topographical maps were used and supported by field surveys. Four stages were followed in Khodabandeh in order to investigate on humus status in the regions. The results were compared using MSTAT statistical soft wares. In order to compare treatments, Duncan test was applied.The results obtained from the studying surface and sub-surface layers of the area show that rangelands which have not been disturbed by anthropogenic activities are classified between irrigated and drylands. It can be said that the irrigated farming, especially alfalfa farming, enhances soil humus content due to nitrogen fixation done in the roots. But, the drylands especially those with high slope cause degradation of soil organic matters, fertility and production yield and also increase soil erodability.