فصلنامه تحقیقات مرتع و بیابان ایران
سال چهاردهم شماره 4 (پیاپی 29، زمستان 1386)

Higher evaporation compared to precipitation in arid zones causes upward movement of soil water and consequently salts will be accumulated in root zone. Since Salt moves with water flow, salt distribution will fallow a pattern similar to soil water distribution. The amount of applied water or leaching fraction is one of the most important and effective factors on salt movement and distribution in soil. This research was established at Yazd Desert Research Station in weighting lysimeters. Salt profile in soils of three hrrhgation treatments: FC, 1/3 FC and no irrigation were plotted and compared with each others for three times (t1, t2 and t3) in this research. In addition soil moisture was also controlled in different ways. The experhment was done in a completely randomized design and Duncan's test was used for comparison of means. Results indicated that soil salinity increased from top soil to deeper layers and this feauture was more significant in fully irrigated treatments specially at the latest times (t2 and t3). Total accumulated salt was also more at more irrigated treatments. High salinity of water and inadequate of leaching, were the most important factors which led to salt accumulation in the deep layers of fully irrigated lysimeters.

In order to investigation forage production of annual medic Cultivars, under dryland farming conditions of Gorgan, an experiment carried out in Chaleki research station in 2003-2004. The experimental design was randomized complete block with 4 replications. Cultivars were Medicago scutellata cv.Robinson & sava, Medicago truncatula cv. Caliph & Mogul, M. sphaerocarpos cv. Orion sphere, Medicago polymorpha cv. Spinless, Medicago litoralis cv.Herald and an indigenous species (Medicago minima). Forage was harvested at %10 flowering and dry matter (DM) production was measured after shade drying. Results showed that, forage production of cultivars were significantly different (P<0.01), also Interaction of cultivars and year were significantly different (P<0.05). Forage production of Medicago scutellata cv.Robinson (2006.4 kg/ha DM) was higher than other cultivars at the first year and Medicago truncatula cv. Caliph with 2230.1 kg/ha DM was produced the highest forage yield at the second year. Based on results, Mogul and Sava during two growing seasons with sustained forage production relative to experiment conditions were more adaptable than other cultivars. The mean of Crude protein amount of Caliph (37.28 gr/mˆ2) was higher than other cultivars.

Recognition of effective factor in mass movements occurrence and mass movements Hazard zonation is one of the most important measures in prevention and reduction of their hazards. In this research flow and chanallized flow hazard zonation was done in Damavand Drainage Basin with 761 km2 area, located in Southern Albours Mountains with using quantitative method. For doing this, first, flow and chanallized flow inventory map of the area which was prepared using air photos with the scale of 1:20000 and 1:50000 and field works, was used. In this map 56 flow,26 chanallized flow and the total of 82 movements were shown. In this research, the effective factors for flow and chanallized flow occurrence were recognized to be as follows: land use, geological formation, rainfall, slope, aspect and elevation. Then by using flow and chanallized flow inventory map and quantification of effective factor in mass movements occurrence, mass movements hazard zonation was done in the area by giving percentages to each sub factor of above-mentioned factors. This process was done by extensional facilities of Arcview which is called "Extension Spatial Analyst". The raster maps of six factors with cellular resolution of. /0014 meters, for flow and chanallized flow were added together, in order to obtain hazard zonation of each movement. For evaluation of hazard zonation accuracy and separation ability of the used method, flow and chanallized flow hazard zonation maps were overlaid with vector maps of flow and chanallized flow inventory maps.

Wilted and dried up stands of haloxylon aphyllumspecies in afforested areas of Yazd has allways been a focal point of natural resources experts. Using various pruning treatments, the effect of pruning on the wideness of canopy cover and vigor of 12-year-old semi-trees of haloxylon aphyllumhad been evaluated formerly. That study had been conducted in two different sections of the forest in the winter of years 1994. One section had shown a tree-density of 125 semi-trees per hectare, and the other had represented a tree-density of 250 semi-trees per hectare. The treatments included cutting at different heights of 70, 35, 10 cm and also no cutting (control). The results of that previous six-year study (1994-2000) showed that pruning increased vigority and regrowth of plants treated with different levels of pruning. The 35-cm pruning treatment was preferred over other treatments. At the end of growing season of year 2005, eleven years after pruning treatments, the same trees were evaluated for the second time. Results of the new study (in 2005) showed that while non-pruning (control) 23-year-old semi-trees are wilted and almost dried up, the semi-trees with pruning are vigorous and healthy. In terms of canopy cover and height, no significant difference was found between trees with different pruning treatment in the 5 years of 2000-2005. There was a significant reduction in the canopy cover and height of non-pruning (control) semi-trees (p<0.05). For the semi-trees which had been cut at a height of 35 cm, the diameter of canopy and the height were 262 and 164 cm, respectively. This semi-trees showed a good resistance against movement of sands and sand dunes.

Vegitation cover is one of the important environmetal factors which can determine desert areas. In this article, we determine desert areas in Tehran province by GIS. In the study area, dominant plant types and some of main ecological properties of them were assigned. Finally, by available information and public characteristics of every plant type, desert area was separated. In this area, we distinguish 43 plant groups that 7 types of them belong to desert areas. This area is 307647 hectares which is formed 16.43 % of Tehran province.

Regarding to the importance and role of enclosure as an appropriate management in the natural resources, specially protection of vegetation cover and the soil of pastures, the effects of different grazing intensities on the vegetation cover changesand chemicalsoil properties in countryside pastures of Esklim Rood district (placed in west of Savad kooh township) was studied. These pastures investigated to reveal the effects of prohibition on the vegetation cover changes and some soil chemical properties at three conditions of Reference, Key and Critical areas. The results show that delicious (Class I) in the reference region, average delicious (Class II) in the key region, and low delicious or non delicious plants (Class III) in the critical region, have the most vegetation cover percentage. So that, perennial and delicious grasses such as Festuca ovina L, Ermopoa persica T. Dactylis glomerata L. had the highest vegetation cover percentage in the reference region but by the increase of grazing, delicious species decreased gradually and average or non delicious plants increased. This study revealed that soil of the reference region which had the highest density and vegetation cover had more organic material, total nitrogen, phosphorus, potassium, and less acid in the surface horizon than that of grazing region. Also, results show that short- term enclosure affected on the protection of soil and vegetation cover due to high productivity.

Proper use from water resources, especially in arid and semi arid rangeland are very important. Water is one of a valuable ecosystem component in rangeland management. In this study for surveying of water suitability, tree models including quality model, quantity and distance model made final model. FAO (1991) method (recommended for land capability evaluation) was used for suitability classification. The study was conducted in Halvan region is located in Yazd province. According to the results, water resources distance and accessibility to water is the most declining factor for suitability. Quality factor is a limiting factor in part of the study area, too. Based up on, areas more than 15km far from water point are not suitable, but less than 6km are very suitable. Proper distribution of water resources increases water suitability and cause better and monotonous utilization of rageland.

Nomadic rangeland system is part of rangeland system in Iran and is inflicted to volatility, like nomadism, during decades. The management of this system is imposed to some changes during the past and the effective factors on this system have caused some challenges and the analysis of these challenges lead to some guidance for nomads. In this paper the changes on the past nomadic rangeland management, recognition of effective factors on this management, the occurred challenges and some clarifications at present time are studied and analyzed. These challenges are disequilibrium of rangeland carrying capacity, population pressure on rangelands, contemporary needs occasionally leading to encroaching to rangelands with covetousness, making nomadic decisions, programs and managements distinctively, incompatibility of technology with ecological nomadic rangeland management, and the lack of guidance role of the government in nomads settle down. This paper propose that the development and clarification for these challenges should be based on local participation, so for that, the nomadic social and cultural condition should be considered. Nomadic rangeland management can be done in presence of local social structure, traditional communication and apply of recognized ecological factors. The simulated nomadic production system based on this management could help the decision makers for better programming in nomad’s community.

Kusalan range is a northwest-southeast mountain near Sarvabad, west of Kurdistan. The habitat includes a complex set of ecological functions and unique mountainous values such as Quercus forests, dense ranges, as well as various springs inside and around the region. So far, there was no study on the bioenvironmental habitat potential. This persuaded us to conduct a research on the habitat and ecosocial potentials according to IUCN categories using data bases like other literatures, 10 m2 panchromatic SPOT5 2005 data, expert opinions and field studies. Analysis of ecosocial and ecological bioenvironmental sources was implemented through a geographic information system (R2V, Arc/Info, Idrisi and Arc View). After qualitative and quantitative evaluation of various sources, land units were observed from overlaying maps of land form, soil categories, vegetation type, wildlife habitats, land use and conventional territory. Illustrated map show that about 70 percent of the area has a great conservational potential thus, the zonation process on the basis of IUCN definitions executed. The studied area was a habitat for 224 species of flora and 195 species of fauna classified as 5 categories: 29% core zone, 41% buffer zone, 14%expanded recreation zone, 3% intensive recreation zone and 14% cultural historical zone of Hawraman city and Pir-Shaliar annual ceremony and 13.2% reclamation zone including scientific, training values, virgin features and unique landscapes. Thus, Kusalan habitat worth to be introduced a national park (II) as a member of quadruplet national protected area in Iran. According to the results, GIS and RS approaches (hybrid interpretation of high resolution SPOT5 images) certainly can support determining and preparing bioenvironmental map sources in impracticable areas for conservational studies on IUCN criteria basis.

Remote sensing technology is useful tool for spatial and temporal monitoring of natural phenomenon. Secondary salinization is known as the main causes of soil degradation where inappropriately land management occurred in a region. Total saline and sodic soils in Hamedan province are estimated at 70,000 hectare that includes 9.5 percent of total cultivable lands in this province. This paper tries to show important aspects of applying remote sensing in classification of sodic soils in Qahavand plain. The objective of this study is to monitor the sodic soils by using satellite information landsat-5&7. Classification of satellite imagery for alkalinity was carried out by investigation various bands and indexes such as PCA57, PCA123, NDVI, GRI, BRI. The supervised classification and spectral response angular mapping method used to classify the images. The soil maps were prepared by geographic information system in 1:50,000 scale. The results showed that total sodic soils areas were extended during last 11 years by 9.8 percent. The change in low sodisity class (A1) was 23.1 percent; in medium sodisity class (A2) was 13.7 percent and in sever sodisity class (A3) was 0.3 percent. The area of bare soils was 3005 hectares which is estimated 8446 hectares now and increased by 181 percent. The most important reasons for extension of sodic soils in this region are lack of proper land use and water management and conversion of land uses.

Knowing forage quality is necessary for assigning grazing capacity in range management program. For this aim, forage quality of two dominant range plants, Artemisia aucheri, and Peteropyron aucheri were studied in water spreading area of Heart station in Yazd province. Plant samples taken for two subsequent years from water spreading and control plots. Plant samples analyzed in laboratory and elements such as P, Ca, Mg, K, Na, Fiber, Fat and Proteins were measured. Statistical analysis indicated that in two years of study period, some elements has increased in water spreading plots (p<0.05), but, acceptable changes in forage quality of the two specie can not be reported.

Remotely sensed data has high potential for characterizing land use/cover types. Traditionally, most of remote sensing image classification techniques are based on pixel-based procedures. In contrast to pixel-based procedure, image objects can carry more attributes than only spectral information. Object-based processing not only considers contextual information but also information about the shape of and the spatial relation between the image region. In this paper, we address the concepts of object-based image processing and presents an approach that integrates the concepts of object-based processing into the image classification and land use land cover type determination. The scheme proposed in this study is applied to classification of Landsat7 (ETM+) data of Kasha area. This study shows the applicapability of object-based approach for classification of Landsat7 (ETM+) data as well as show high overall accuracy (95%)of land use/land cover map. From the obtained results, we concluded that the main land cover types of the arid region could be discriminated with a high level of accuracy by object oriented approach