IRANIAN JOURNAL OF RANGE AND DESERT RESEARCH
Year:2008 | Volume:15 | Issue:1 (30)|Papers Count:14

More than one-third of land in the world is located in the areas with arid and semiarid climate and desertification has increased in these areas during recent decades. Around 80% of Iran is located in arid and semiarid areas. Sand dunes as an indicator of desert land cover an area about 32 million hectare. Among which 12-mil hectare has not been stabilized yet. Advancing moving sand dunes has resulted in much damage to agricultural products and urban areas. In this survey satellite images and aerial photos are used to evaluate the role of land use changes on desertification in 1955, 1997 and 2002. To do so, IRS image of 2002 and available aerials photos of 1955 and 1997 are used. Following making the aerial photos mosaic processing was done using ILWIS software and needed data completed by field surveying and the land use map was produced for two years. To produce the land use map using digital processing methods 10 sample set (training points) were selected uniformly in the area. After preprocessing including geometric corrections, image enhancement and band composition, image classification was done by maximum likelihood method and the land use map was produced. In this phase, obtained land use map was corresponded to the ground truth map which was achieved by field surveying and recording coordinate of points with GPS pixel to pixel and accuracy obtained from numerical classification estimated to be 45.3%. Then due to obtained low accuracy, the visual method used to produce the land use map so the accuracy of 78.5% achieved. Finally, the area of each land use and the rate of changes were calculated. The results indicate a decrease of 2000 ha in the area of the desert land from 1955 to 1997 and of 160 ha from 1997 to 2002 and an increase in the area of the other land uses. Results show no desertification in the study area, even though land degradation can obviously be identified in the area, which is resulted from the changes of gardens, and agricultural land uses to industrial and urban areas.

The major objective of this research was to evaluate the effect of the 5-year exclosure at Goladam station of Salmas rangelands Vegetation type and dominant species of this area was Bromus tomentellus and Festuca ovina. Changes in total forage production, plus canopy cover percentage, range condition and trend of this rangeland were measured, evaluated and then analysed statistically. Results of this study indicated that range condition and trend of this rangeland improved considerably. Total plant covers and forage production of the protected area increased. Vegetation cover and density of the plant species class I and II increased while species class III decreased considerably throughout the study period. It seems that the 5-year exclosure is an appropriate exclusion period for this area. Further investigations are recommended for find decisions.

In wind erosion process, there are three areas: source area, transport area, and deposition area. The prevention of sediments movement in the source area is a fundamental task. In stabilizing source sediments of sand dunes, recognition of the taking regions is essential. In order to study the in order to study the source of eolian sediments in the Fadisheh region, a step-by-step method (Ekhtesasi-Ahmadi) was used. This study was done in two stages: direction finding and location finding. First, information about the direction of local winds was gathered by questionnaire. Then satellite image (ETM+, 2002) and field investigations, the erg morphological map was determined. By studying wind regime and wind rose drawing, the erosive winds were recognized. After recognition of source sector (southeast and east sector), the location finding phase was started. In this stage by geomorphologic studying of the source sector and sampling into facieses, the mineralogical and morphoscopical studies of sand dunes and source sector sediments were done. Finally, paying attention to other evidences as the direction of Barkhan dunes (Southeast-Northwest), high intensity of energy for East winds, the existence of heavy minerals as Hematit, Chamosite, Edenite and Sphalerite in sand dune and source area soil samples, average median of sand dunes sediment samples (~210micron), symmetrical shape of sand dunes sediments frequency graph, was found that the source of eolian sediments are in the middle distance relative to sand dunes and are as follows: damaged Haloxylon forests, non vegetative area, unutilized lands in the southeast sector of the clay plains, Microlithic pediments and non vegetative lands in the margins of Kal-e-Shoor and Kale- Shoor River bed.

Determination of grazing capacity depends on information about various factors such as forage quality and species nutrient values, and for achieve to ideal animal production information about nutrient value are very important. In this trial, nutrient values of twelve species were to evaluate, that were grazed by Mehraban sheep in two phenological stages (vegetative and maturity) in two sites of AghDagh & Galebor at Hamadan province. Forage quality indices as Crude protein (CP), acid detergent fiber (minus Hemicelluloses) (ADF), dry matter digestibility (DMD) and metabolisable energy (ME) were measured respectively.According to the results, significant differences were observed among the species and phonological stages for all measured and calculated forage quality factors (p<0.05). Generally, Information about forage quality factors is essential for animal nutrition management in rangeland and it should be considered in range and animal management designs.

Weighting lysimeters are good instruments and direct method to plants water needs (evapotranspiration) in arid zones. This research practiced at Yazd Shahid-Sadooghi Desert Research Station. Ten galvanized iron lysimeters (120 cm. diameter & 170 cm. high) were made and constructed after covering with a glass-wool layer to minimize the effect of the environment temperature variation on them. Four hatchways installed at different depths (30, 60, 90 and 120 cm) of lysimeters for root and soil sampling and estimating of soil moisture content by TDR instrument. These containers became full with disturbed local soil (1.s tex.), planted and irrigated respectively at the beginning. Lysimeters weighted by a portable liftract which was linked to a powerful (5000 kg. capacity) and accurate (0.1 % sensitivity degree) balance. Drainage water also collected from outlet tubes below of lysimeters occasionally. Results has shown that this procedure have had a good efficiency because achieving to objectives of this research was available. Saving and analyzing of information by computer and with change of weighting method, would also be probable in the future.

This research was done in order to investigate the seed age effects (longevity) on germination of some sagebrush of species. East Azerbaijan was chosen as the collection sites and seeds of four species such as Artemisia fragrans, A. spicigera, A. campestris and A. vulgaris were collected from these sites. Seed germination of these species was tested in the spring of the three following years and the data analyzed statistically. Results showed that seed ages have positive effects on the viability and germination of all species under study.. Minimum and maximum changes in seed germination belonged to Artemisia vulgaris and Artemisia spicigera respectively.

Zabol region is one of the places that is exposed to severe wind erosion, which is located in southeast Iran Due to the fact that, some stations like Zabol suffers from missing data (having five observations instead of eight), thus, the effects of missing data on prediction of wind speed and direction also needed to be considered. This study aim to determine the minimum years of data required in predicting hourly wind speed and direction, and predicts hourly wind speed and direction, also to verify suitability of Weibull distribution in predicting hourly wind speed and direction and finally to analyze the erosive winds in Zabol region. In this study, the regression coefficients (r) of probability of wind occurrence in various speeds for 16 cardinal directions in two different periods (1986- 1990 and 1986-1995) were separately calculated and compared. To predict hourly wind speed and direction by Weibull distribution, at first its scale and shape parameters (c and k) were determined using the least square method. Then, wind direction distribution, the ratio of maximum to minimum of wind speed, and the hours with maximum wind speed during any month were determined. Using these parameters along with generation of random numbers, the hourly wind speed and direction were simulated. The results indicated five years instead of ten years of data can be used to predict wind speed and direction with a confidence level at 99%. Weibull distribution provided best fit during the months that both the probability of calm periods or standard deviation of probability of wind occurrence in different directions were low. The maximum and minimum wind speed occurred at about 6:00 AM and 6:00 PM, respectively. The probability of occurrence of erosive winds (V³8m/s) were maximum in June, July, August, and September. The analyses of wind data indicated that the most erosive winds were from North-Northwest, Northwest, and North. The wind speed and direction were predicted by Weibull distribution in the region with 99% accuracy. The results obtained from this research can help researchers and soil conservationists to predict and control wind erosion.

Studying the behavior and the way a plant species functions, and investigating on its relationship with biotic and abiotic components of its habitat is considered as autecology of that plant species. This type of studies provides valuable information which is necessary for rangeland ecosystems management. This research was conducted to study the autecology of Stipa barbata. In this study, some topographic, climatic, and edaphic characteristics of the rangeland ecosystem, in which the plant species grows, were determined. Names of accompanied plant species in the ecosystem were listed. Based on physiognomy, this plant is the dominant species in most of its habitats. Its canopy cover, density, and frequency are 4.5%, 32750 plant/ha, and 82.5%, respectively. Phenology, root system, and the way of presence of Stipa barbata in the ecosystem were evaluated. The results showed that the habitats of this species are located in elevation range of 890 to 3300 meters above sea level while the major habitats are including elevation range of 1100 to 2800 meters above sea level. The species grows on slopes of 0.5 to 100%. Mean annual precipitation is 221 mm and 485 mm in Eshtehard and Zidasht Taleghan, respectively. Mean annual temperature is 15.5 and 24.5 degree Centigrade in Firoozkooh and Rood Shoor, respectively. The habitats for this plant species include very shallow to deep soils. Vegetative growth starts in early March and ends in early April. Its flowering stage is from mid May to mid June. Seed ripening stage is from late June until mid July. The plant has a shallow fibrous root system. 

Resistant species to salinity and aridity and temperature fluctuation are approximately introducer of desert. These species have particular morphology compatibling themselves to fragile and acute condition of desert area. Some species accumulate water in their tissues. Some other species decrease leaves area and develope their root systems to use groundwater resources and some have particular phytocynthesis systems. As a general desert species with different mechanism resist against acut climate condition and unsuitable soil properties of desert regions. Characteristics of desert species distribution area can be determined the geographical domain of desert area. In this study dominant plant types in certain gropes and some of main ecological properties were assigned and related map in GIS environment was prepared. Finally, according to public characteristics of dominant species of every plant type and accompany species, desert area was sperated. In study area 22 plant group, each consist of some plant types was recognized. The distribution area of plant groups of Zygophyllum atripolicoides, Gymnocarpos decander and Hammada salicornica is about 730132, 599941 and 53260 hectar respectively.

Desert wheatgrass, Agropyron desertorum (Fisch. ex Link) Schult, is one of important perennial grass species that naturally grows in Zagrous and Alborz mountains rangelands in the west and north of Iran. In order to identification of superior genotypes for both seed and dry matter (DM) yield, 31 genotypes were sown in two separate experiments under optimum and drought stress condition using randomized complete block designs with three replications in Arak, Iran, during 2004-2006. Seeds and DM yield in optimum (Yp) and stress (Ys) condition for each genotypes were used to estimate the five drought resistance indices as: tolerance index (TOL), stress susceptibility index (SSI), mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI). The data subsequently used in principal components analysis. Based on bi-plot of the first two principal component scores, genotypes were distributed into four groups. For seed yield 631P5, 747M, 747Pll and 213Pll with average values 430 to 503 kg/h and for DM yield, 3477PM, 3477PM, 3965Pll and 341Pll with average values 2060 to 2260 Kg/h were recognized as the best varieties for dry condition. The 742P5, 1369P6, 3477P4, 287P8 and 341M for seed yield and 3477M, 3965P15, 631P2, 4036M and 341PIl for DM yield were introduced as the best genotypes for cultivation in semi arid regions. In simultaneous selection for both seed and DM yield, 631P5 (Ghazvin), 747M (Ghazvin), 341M were introduced for arid regions and 3477P4, 341P11, 287P8 (Ramadan), 1369P6 (Ramadan) and 3477M for semi arid regions of central province of Iran.

In order to improve seedling growth and establish alfalfa in arid and semi-arid regions of Iran a factorial experiment was conducted using 3 alfalfa varieties and 2 levels of Sinorhizobium strains with 4 replications in Alborz Research Center. For this propose nitrogen fixed nodules were collected from root of alfalfa plants. They were washed several times with distilled water and then were sterilized in the laboratory. Seed samples were inoculated by Sinorhizobium strains solution and then they were sown in plastic pots containing sterilized sand. Data were recorded and analyzed for seedling characteristics of alfalfa such as plant height, root length, seedling length, stem dry weight, root dry weight, seedling dry weight, and nodule number per plant. The results showed significant effects (P£1%) of Sinorhizobium strains on nodule number, seedling height, root length and seedling dry weight (Biomass).The results of correlation analysis showed positive and significant relationships among nodule number with root length, seedling length and seedling biomass. It was concluded that the effects of seed inoculation, not only improve seedling establishment, but also increase forage yield and soil fertility. Therefore, it is recommended that inoculation of proper Sinorhizobium strains with alfalfa seed could be possible to extend cultivation area of alfalfa in arid and semi arid regions of Iran.