IRANIAN JOURNAL OF RANGE AND DESERT RESEARCH
Year:2005 | Volume:12 | Issue:3 (20)|Papers Count:8

It is necessary to recognize the ecological characteristics of dominant species in desert and arid ecosystems for plant conservation and sustainable utilization. In this study botanical and ecological characteristics such as root extension, phonological stages, distribution sites, habitate conditions, vegetation composition, plant regeneration and grazing of Hammada salicornica were considered H. salicornica is a perennial plant belonging to chenopodiaceae family in which distributed in vast areas in the south of Iran.Hammada is a dwarf shrub with multiple stems and succulent leaves.Generally the only main root extends vertically in fine soils. It grows in soil containing large amount of gypsum or lime with fine texture. Hammada is observed in many plant communities as dominant or accompanian species: It is distributed from about sea level up to 1800 meter of altitude in areas with annual rainfall between 60 to 300 mm. Phonologically, the growth starts in late winter and reaches to flowering and maturity in early and late autumn, respectively. The regeneration of plant is from seed in natural habitats. It is grazed by animals mainly in the end of growing season. In general this plant has a good perspective for using in desert reclamation.

In order to evaluate of soil physicochemical characteristics by using seasonal flood at Tangestan research station in Boushehr province, 3 sites among of 10 sites (1200 ha) were selected. Two treatments (with and without water spreading) in each site were applied and 30 soil samples from 0-25 cm depth in each treatment were taken. Soil samples were analyzed for texture, bulk density, particle density, saturation percentage, total porosity, electrical conductivity, pH, organic matter, total nitrogen, calcium carbonate equivalent, solution cations and anions and sodium absorption ratio. The Factorial design with 2 factors (water spreading and site), was selected as the statistical design and the results were compared, by Duncan' s test. The final results showed that the soil texture has become heavier about one class; sand was decreased, silt and clay were increased due to floodwater spreading (significantly at 1%). The changes of soluble ions, total nitrogen and organic matter showed an increase without statistical significance. Total porosity, pH, and SAR amounts were not significant.

Investigation of documents and references related to desert pattern shows that there is not any integrated definition for deserts. In this article, by considering the climatic factors, desert and non-desert areas have been determined. For this purpose, after identification of climatological stations in Esfahan province and investigation about their statistics quantitatively and qualitatively, 46 stations with enough data were selected. The related maps were prepared in GIS. The factors for desert identification could be found mainly among those, which compose desert climate. The amount of precipitation, coefficient of variation, irregularity coefficient and daily average intensity of precipitation, annual average temperature and amount of evaporation are the factors which were calculated for each station separately.By use of averaging method, the isohyet's maps were prepared for each factor. Through determination of a number as a scale for distinguishing of desert and non - desert area for each map and checking them on the site and overlaying the maps, a buffer were made between the verification lines which did not coincide with each other. As the result, 3 different zones could be distinguished on the final map. The internal zone resembles the specifications of desert, outer zone non - desert and the zone located inside the buffer as semi - desert area. The result of this research shows in Esfahan province, desert, semi desert and non desert areas are 4840450, 1775412, 4840450 hectares respectively.

Range condition can be considered as an important indicator of management assessment. Method known as four factors was used to assess range condition each year. Some important communities of Yazd province were selected. In each community a key area was determined. Fifteen key areas were selected in whole province. In each site for every year, soil erosion, canopy cover, plant composition and vigorey of plants were monitored. The result showed no significant difference between above mentioned factors during five years (p> 0.05). However, factors significantly varied between sites in different years. In spite of constant vegetation condition trend rainfall varied among years. So marks recorded for each factors during the period of study were compared using principal component analysis and clustering. Sites in terms of condition, vegetation cover and soil were classified. Correlation between value of each factor and condition value showed that vigorey had no significant relationship with range condition by these sites. Generally Yazd's rangelands classified in poor to fair condition with constant range condition trend in period of five years.

This experiment examines the influence of rock fragments on soil erosion, sedimentation and percolation of water through soil profile.Laboratory experiments were carried out to control the effect of stone cover percentage on runoff and sediment yield using rainfall simulator and small flume facilities. 312 series of experiments were conducted on two different soil samples taken from Saveh and Amameh catchments. Saveh soil was a light soil with a sandy loam texture and soil samples from Amameh catchments had a clay loam texture. For all experiments approximately 100 Kg of soil sample was packed in the 1x1 meter flume's tray and leveled manually. For each experiment, four slopes ranging between 5 to 20 percent and three-rainfall intensity of 25 to 75 mm/h were used with six different treatments of stone fragments ranging from 10 to 60 percent cover. Two types of stone-cover placement were used namely at rest and embedded position on the top of soil surface. Runoff water, sediment yield and percolation water were measured for each run. The effect of rock fragment on infiltration rate, runoff and sediment generation are proportional to cover percentage. Despite the general assumption that the existence of rock fragments on soil bed would decrease the sediment yield, the result of this experiment showed that when sediment concentration plotted against stone cover percentage at different slopes and rainfall intensities, it was found that the relation between sediment concentration and stone cover content was not linear. In the other word there is a convex-upward relationship with highest runoff and sediment yield at 15 to 20 percent of rock fragments for Saveh and Amameh soil samples respectively. As stone cover percentage increases above 15 to 20 percent, sediment yield decreases sharply becoming minimum at 60 percent stone cover. A second order equation would fit this relationship with R2=0.79 and 0.55 for Saveh and Amameh-catchment soil respectively.

The main objective of this study was to determine the effect of Atriplex plantings on soil characteristics of different locations of Gorgan region. Five locations were chosen and soil profiles were performed, samples were collected, analyzed and compared with control area.Results show that the positive and negative effects of planted Atriplex species on soil characteristics based on different environmental conditions which major may not be favorable for that site and the planted species.By Atriplex planting in the rangeland areas of Maravetappeh and Chaparghoymeh the salinity of the soil were increased, but in Dashliboron, Chaat and lncheboron, salinity of the soil decreased. Other soil parameters, like organic carbon, Nitrogen, Phosphorous, Potassium, ect. were also changed in the same manner.

The main objective of this study was to determine seed germination rate of Aeluropus lagopoides and A.littoralis. Accesion. In this Study we have used factorial complete randomized design with Seven salinity rates of 0, 75, 150, 225, 300, 375 and 450 Mm NaCl. The experiment was carried out for germination test with 70% relative humidity at 25°C with a Photoperiod of 14:10 hrs light/dark. Germination percentage was measured, and the data were analyzed by one- way ANOVA and Duncan's multiple range test. The results showed significant effect of salinity on germination percentage. Despite high tolerance of halophyte to salt, the maximum germination occurred in salt free treatment. Aeluropus littoralis was more resistant to salt.