IRANIAN JOURNAL OF NATURAL RESOURCES
Year:2007 | Volume:60 | Issue:2|Papers Count:29

Soil erodibility is one of the key factors affecting certain sediment and soil erosion models such as USLE, RUSLE and MUSLE, and is represented as K factor that is the function of particle size distribution, organic content, soil structure and permeability. Traditional methods do not depict spatial displacement and fail to provide information on the precision of approximations by these methods. This study was performed to assess spatial variability of soil erodibility and its relevant variables in Mehr watershed, Sabzevar. The sampling network included 110 nested-systematic points with distance about 50, 100, 250 and 500 meter across the study area at GIS. Sampling was done at depth of 0-5 cm beneath the ground surface and permeability was studied at depth of 5-30 cm. Some soil properties such as particle distribution and organic content were measured at laboratory. Spatial variability of these variables were examined with means such as variogram models, kriging and error maps. Statistical analysis of the soil shows that the studied variables following the gaussian, exponential and spherical models and their range were changed from 320 to 3,200 m. Soil erodibility magnitude ranges from 0.13 to 0.91 and maximum and minimum values were identified in the east and southwest of the studied area. Soil spatial variability pattern is highly corresponds the silt pattern due to high effect of silt on soil erodibility. Spatial variability pattern is also in agreement with geological maps satisfactorily that reveals parental materials controls erodibility of soil with respect to the soil's type.

The spatial resolution of satellite data in determining the area covered with snow was examined in this research. For this purpose, the Advanced Very High Resolution Radiometer (AVHRR) of NOAA satellite, with a nominal resolution of 1,100 m and the TM radiometer of Landsat satellite, with the nominal resolution of 28.5 m, were chosen and the data provided by them were compared. According to this research, which focused on snowy areas of Karun river basin in Iranian Zagros mountain range, the approximate areas derived from images of snow-covered regions produced by NOAA and Landsat satellites in two different dates, one at the beginning of the snow melt season and another at the end of this season, show a discrepancy by 15% and 17%, respectively. Furthermore, the research shows the spatial overlap of polygons by the two satellites is considerably less than the overlap of the images. However, the overlap area in various polygons is significantly correlated with the total area of the snow-covered region. Additionally, as the spatial resolution of satellite data reduces the risk of overestimation of snow-covered area increases. Another issue that must be considered is that only if the size of snow fields must at least is equal to some pixels as viewed by the radiometer distinguishing the fields will be possible.

This study conducted to compare different watershed operations such as pitting, ripping and contour furrow for water conservation in soil and plant cover by using experimental plots in order to determine suitable operations. Random complete blocks carried out this study with eight treatments (pitting, ripping and contour furrow with and without seeding, plot with only seeding and control plots) in three replicates. Plots dimension were 8*40 meters with 6% slope. The two features of soil moisture and plant cover were considered. Soil moisture was measured in 0-50cm depths physically by using sampling cylinder and auger and subsequent drying and weighing the samples. The results derived from statistical surveys showed that at the probability of 1% the samples fall into two categories (a and b) while at the probability of 5% three categories (a, b, c) appear. Maximum soil moisture was observed in contour furrow and pitting with 8.82% and 8.52%, respectively, and minimum was found in the control sample with the value of 7.24%. Plant cover and forage production in two consecutive years were investigated. The results showed again that in the 5% probability three categories may be distinguished (a, b and c) while at the 1% probability two categories (a and b) forms. Maximum plant cover was observed with pitting with seeding with 44.66% and the minimum was found with ripping without seeding with15.891%. Finally, it is concluded that favorable plant cover may be developed in heavy-texture marly lands by building furrow and pitting construction. Rainfall water and soil conservation is another advantage of using these initiatives.

Erosion is one of the most important threats to natural resources and agricultural lands. In this connection, preparing erosion form maps is most urgent than preparing maps of erosion intensity. For this purpose, various sources, especially geomorphology maps, aerial photos, and satellite images are used in this research. Making field surveys is also highly helpful. The frequency of field survey is usually in accordance with the scale of maps but there is no standard procedure for field surveys. This research, which was carried out in Merek area, Kermanshah Province, is aimed at examining the practicality of the images taken by Cosmos Satellite for geomorphologic studies and preparation of erosion forms maps with a scale of 1:50000. For this purpose, after preparing the erosion forms map and interpreting the Cosmos satellite's image and geomorphologic facies (by GIS), five sloping amplitude in each facies were chosen for field studies. A conclusion based on comparing photos and field studies shows accordance between the photos and results of field study was above 70% when waterways, gullies, and landslides were considered while this conformity for sheet and traces erosion was acceptable to some degree. The comparison showed conformity between the two methods for rills and snow erosion was below 50%. Additionally, the photo is not able to reveal piping erosion. The result of comparison between sloping amplitude in facies for initial conformity degree more than 70% in 29 facies, 60%-70% in 34 facies and less than in 14 facies. Therefore, boundaries of the facies should be adjusted according to field studies and make slight corrections in the second state. Concerning the third state, the facies should be converted into two facies.

In order to assess the current desertification intensity caused by water erosion and to present a desertification regional model, a study was carried out in Mahan basin (Kerman province) in a 90,253 ha area. In this study، based on existing domestic and international methods including FAO-UNEP and ICD, which are most well-known methods at home and in the world, an integrated method was developed. Moreover, it was tried to apply some modifications regarding the current situation of the region. In this case, work units (facieses) were designed based on the geomorphologic studies. Then, proposed model was employed in each unit and subsequently in the whole area. In this study, only the current situation of desertification along with human and environmental aspects was studied. The desertification intensity was classified into four classes: low, average, high and very high. The results showed that 35.57% of the area is threatened by desertification at a moderate rate (class II) and 64.43% of have underwent severe desertification (class III). It also revealed that environmental factors contribute to the desertification process much more effectively than human factors do.

In this research, the HEC-RAS model and its extension HEC-GeoRAS and their applications and capacities, as well as combination with the ArcView software, and introduced and flood zoning concerning the flood plain of Babolrood River was studied and damage to the plain as the result of floods was assessed. For this purpose, maps with 1:1000 scales were prepared and the study began in 103 sections within 5.5 km along the river. Hydrological data were collected and based on the Cawen method the roughness coefficient was determined in ten areas with approximate 500 meter distances between the points. Employing certain methods and operations, maps of the area, depth and velocity of floods in seven flood occurrences in 2, 5, 25, 50, 100 and 200 years ago were prepared, and damage to adjacent rice fields was assessed and related damage curves were drawn. The results had shown that about 89.53% of the flood area over past 200 years is prone to flooding according to the patterns in last 25 years. The damage curve shows that the rate of damage increases with the increase in the flooding depth up to the medium depth (2.82 m) while the damage rate decreases in medium depths more than 2.28 m. among Babolrood section 1, Babolrood section 2 and Sajjadrood, the highest depth of flooding is found in the Babolrood and the velocity of flooding in sections 1 and 2 of Babolrood is higher than the velocity in the Sajjadrood section.

In this research Quaternary Deposits of Taleghan Drainage Basin were investigated, related map was provided and their erodibility was determined. The most widespread Quaternary Deposits of Taleghan Drainage are alluvial terraces which are as follows from the higher elevations to present alluvial river: ˝ Mindel˝ Terrace, ˝Riss˝ Terrace,˝ Wurm˝ Terrace ,˝ Toria War˝ Terrace . The erodibility of alluvial terraces and alluvial fan deposits were investigated by different methods. For this purpose, in the case of ˝ Riss˝ and ˝ Toria war˝ alluvial terraces having thin soil horizon, modified –K parameter in USLE model and rainfall simulator were used. For ˝ Mindel˝ and ˝ Wurm˝ Alluvial Terraces and Jazan– Varkesh Alluvial Fan having thick soil horizon, K parameter in USLE model and rainfall simulator were used. The results of this research have shown that the most widespread Quatenary Deposit of Taleghan Drainage is ˝ Riss˝ with 2743 hectars and 2.4% area. Alluvial Terraces are mainly found in the center of Drainage basin. The amount of modified K parameter in ˝ Riss˝ Terrace is 0.12 and in ˝ Toria War˝ Terrace is 0.17. The amount of K in ˝ Wurm˝ Terrace is 0.23, in ˝ Mindel˝ Terrace is 0.16 and in Jazan–Varkesh Alluvial Fan is 0.05, the order of erodibility from the highest to the lowest is ˝ Wurm˝, ˝ Toria War˝, ˝ Mindel˝, ˝Riss˝ Alluvial Terraces and finally Jazan–Varkesh Alluvial Fan. The order of erodibility from the highest to the lowest according to rainfall simulator is: ˝ Toria War˝, ˝ Wurm˝, ˝ Riss˝ and ˝ Mindel˝ Alluvial Terraces and finally Jazan–Varkesh Alluvial Fan. In conclusion, except for very coarse–grained alluvial terraces in which there are difficulties in using rainfall simulator, the results from K parameter in USLE model and rainfall simulator are in accordance with each other.

Thirty-five core samples were taken from 35 stems of oak (Quercus castaneafolia C.A. (Mey.)) in Noor Forest Park. Associations between tree-ring chronologies with 85 climatic variables, including precipitation, temperature, evapotranspiration and water balance were examined on an annual, monthly, three-seasonal and growth season basis. Simple linear and multiple regression models were run to evaluate and to estimate impacts of climatic variables in current, and first, second and third preceding years on the growth of oak. Filtration method was used to find the best. Statistical factors, such as coefficients of variations and determination, and residual sum of squares in different subsequence process were attained. The best model for evaluation of the growth of oak could explain total variance by 88 percent. The response of this species was different in different years. The filtration method helped identifying and using the best models in each step. Based on this method, it was understood that the oak's growth responds chiefly to the current climatic variables rather than those of previous years, though there was a correlation between growth and the variables in the last three years, but to a lower extent. The result of this study showed that Caspian oak favors warm weather in the growth season, and growth will be different depending whether climatic variables are favorable or not in the current year and the last three years. Based on the research, climatic conditions of the current year have a greater effect on the tree's growth as compared to the conditions of previous years.

Forest harvesting is a system and the most expensive part of forest management. The main objective of the harvesting engineer is to minimize harvesting costs and damages. To manage such operations properly, it is necessary to understand the components of the harvesting system. Felling is one of the components of the harvesting system, which is carried out by means of power saw in Iran. Tree felling by power saw was studied in Patom Section (113, 116 and 118 compartments) of Kehyroudkenar Forest Research Station using elemental time study method, and felling model was examined. The results of the study indicated that the DBH is the most effective factor on felling time and consequently the cost of felling. Felling time or cost has a positive linear relation with DBH. The chainsaw working team, including one feller and two workers, fells 7 trees per hour in average with cost of 309,785 Rials per day.

Using animals is an old method to transport logs from the stumps to the landing. This method and its cost and destructive side-effect have been studied in countries such as the United States of America, China, India, Chile and European countries. Mules are widely used for transporting billets, firewood, pulpwood and lumbers in Iran. This research was conducted in Aban 1381 (November 2002) in Kheyroudkenar, Nowshahr. After defining the elements of the work, in order to assess the cost of log production and transportation by mules, the continuous time study was used and the models of transporting billets, firewood and lumbers by means of a V-shaped tool were developed. The quantity of produced and hauled billets was 2.135 m3/h that increased to 3.275 m3/h when the V-shaped tool was used. The amount of pulpwood hauled in this way was 1.246 m3/h. According to the agreement with the contractor, the price of hauling billets was 13,382 Rial/m3 that reduced to 8,724 Rial/m3 when the V-shaped tool was employed. The price for hauling pulpwood was 28,663 Rial/m3. In average, based on calculations and regarding cutting procedures in Patom and Namkhaneh, 88.37% of the products is produced using the traditional method and only 11.63% of the products is processed by mechanized methods.

In this research, nonsexual propagation of Iranian maple (Acer velutinum Boiss) through stem cutting was studied, and a statistical survey called random split plot method was used in analyzing the results of the research that was carried out in the nursery No. 1 of the Shastkalateh Research and Experimental Forest Station (Dr. Bahramnia). Another group of the stem cuttings were planted under greenhouse conditions. The cuttings planted were treated with IBA at concentrations 0, 1000, 5000, 10000 ppm. The results were analyzed according to the Duncan test (at 5% level). The results showed that Iranian maple may be propagated in both ways. Furthermore, the hormone at concentration 5000 ppm produced results that were significantly different from other treatments up to 5%. Providing and planting the cuttings in late Azar (late December) also causes a significant difference up to 5% with providing and planting the cuttings in late Esfand (late March). This treatment shows better results in the greenhouse as compared to the nursery, and 76.61% of cuttings have developed roots.

Understanding laws of growth and development, the interaction between structures and natural factors, and evaluating potentials of ecosystems is the first step is providing a well-founded management to meet economic and social needs and help natural ecosystems to preserve their dynamism. Site classification, with respect to ecologic factors, can act as a criterion to assess the quality of forest ecosystems. This research is aimed at classifying sites based on plant associations, and has been carried out in the educational-research forest of the University of Tehran located in Kheiroudkenar, Noshahr. The Braun-Blanquet method was used to study the plant associations. The data on plant associations were analyzed by the ANAPHYTO software product. The associations existing in the region were determined. The associations were classified according to the species arranged in the phytosociology table. Results of the research show that two plant associations may be recognized in this region, while each includes a subassociation:1. Rusco-Fagetum and its subassociation Mercurialietosum perenni and its distinguished species….2. Carpinerto-Fagetum and its subassociation Epimedietosum pinnatii and its species named …..

To perform road construction operations and guarantee the stability of roads it is imperative to examine soil mechanical characteristics and determine the soil's technical specifications. In this study, the mechanical features of Gorazbon Forest section have been investigated. For sampling, pedologiy maps were used and different soil classes, slope classes and aspects were combined. One sample was provided from each section and the samples underwent mechanical soil tests for moisture content, soil texture, and Aterberg limits. Then, the samples were classified based on USCS method. Samples were categorized into two general CH and CL classes. The CH class was divided into two subclasses as CHL (with liquid limit of 50-70), and CHH (liquid limit above 70). In terms of plasticity, the samples were classified as plastic (PI=15-35) and highly plastic (PI> 35). These soils had high cohesion rates and considerable moisture. Drainage in plastic and highly plastic was low and very low, respectively. Their formability was also high. Liquid index of the samples were between 25-50, which means that this soil can be used as the construction material only in dry climate or when its moisture is low. It can also be used as subgrade material but the risk of sinking will do exist. Regarding this rang of liquidity index; the vehicles moving in these roads should be strictly limited to four-wheel drive and rubber-wheeled ones.

In this research, variation in the lipid content of grass carp (Ctenopharyngodon idella) during 20 days of storing it in ice was investigated qualitatively. The quality of the fat of the grass carp, in terms of oxidative and hydrolytic deterioration, significantly reduced over the storage period (P < 0.05). Also statistical analysis showed significant increase in peroxide value (PV), thiobarbitoric acid (TBA) and free fatty acid (FFA), and significant decrease in heme iron (HI). The quality and freshness of the meat of the grass carp was reported good to excellent until the fourth day and as well good to acceptable until the tenth day according to sensory evaluation of texture, general appearance, eye, color and smell of gills.

In this study, preservation of rainbow trout (Oncorhynchus mykiss) sperm and effects of preservation duration and antibiotics and activating solutions on the fertility of sperm were investigated. For assessing the effect of antibiotics on fertility two samples – one including antibiotic and another without antibiotic – were devised. In the first sample, sperms were treated with a solution containing 250 IU/ml penicillin and 250 mg/ml streptomycin sulfate, and in second treatment, sperms were put in plastic plates without being treated with antibiotics and were stored in a refrigerator (2-3oC). Sperm and zygote fusion happened 0, 6, 8, 12, 19 and 25 days after storage in refrigerator. Water and Billard saline solution were used at the time of fusion to evaluate the impact of the type of activating solutions on fertility. The results showed that eyeing and hatching rates decreased with the storage duration. These differences were not significant between zeroth and 6th days (p > 0.05), but after 8 days of storage, significant differences (p < 0.05) were observed. There were not significant differences in eyeing and hatching rates between the two samples (with and without antibiotic) until day 12 of storage, but significant differences were noticed between the two samples (P< 0.05) on days 19 and 25. In all samples, Billard saline solution produced higher fertilization rates as compared to water. In water-treated samples, eyeing rate decreased strongly from 89.06 to 12.15 and zero percent on days 0, 19 and 25, respectively, but in the samples treated with Billard saline solution, fertility decreased from 98.86 percent on day 0 to 74.63 percent on day 19 and 79.78 percent on day 25.

In this research, based on an experiment, the number and size of malpighian bodies in juveniles of Caspian Sea brown trout (Salmo trutta caspius Kessler-1877) with different weights placed in solutions with various salinity were studied. For this purpose, juveniles with weights 2, 5, 10, 15 and 20 g were directly transferred to saline solutions with concentrations 0, 4, 8 and 12.5 g/L and were kept there for a period of 120 hours. By observing the results of histological changes, it was shown that the number and size of kidney malpighian bodies increase when the weight is increased. Also the number and size of kidney malpighian bodies are decreased when salinity increases. The results of mortality percentage until 120 hour shows that the juveniles of 2 up to 20 gr have no mortality in water salinities ranges of 0 up to 12.5 gr/lit which is a cue to the fact that they have a remarkable adaptability to the environmental condition changes. Considering the sub target of this study that is determination of the proper weight and salinity for releasing juveniles Caspian sea brown trout as well as the obtained results of the experiment, it seems that juveniles of 2 up to 20 gr could be directly released in salinities of 0 up to 12.5 gr/lit and it is predictable to survive at such condition. But due to the fact that releasing the juveniles with higher weights in salinities near to seawater salinity by having an eye on the reduction of staying time in freshwater and also the reduction of the distance between releasing area and the sea could be helpful for the success of releasing process, it is recommended to release juveniles caspian sea brown trout of 10 gr which showed the proper histological changes among other weights as well as no mortality in salinities of 8 up to 12.5 gr/lit (same as estuary to seawater salinity) to achieve the proper releasing process.

Fruit and vegetable markets in Tehran are managed under the supervision of Fruits, Vegetable and Agricultural Products Wholesale Markets Organization. There are eight wholesale markets, including 327 stands in Tehran. In order to examine the waste produced in wholesale fruit an vegetable markets in winter 2002 and summer 2003 qualitatively and quantitatively, sampling was carried out as minimum and maximum and in a random mode. The average percentage of the components of the waste materials and their specific gravity and chemical composition were determined as follows: fruit & vegetables 84.35% , glass 0.19% , wood 3.85 %, paper, card board and carton 3.59 % PET and plastics 3.03 % , metals 0.19 %, bone and protein materials 1.50 % , dry bread 0.40 % , fabrics 0.50% and miscellaneous materials 2.35 %. Average specific gravity of the waste is 283.3 (kg/m3). Results of the chemical analysis of the waste produced in wholesale fruit and vegetable markets were as follows: moisture 80.94% , salinity 9.33% , acidity (pH) 5.52% , SP 88.75% , OM 65.88% , ash 29.19 % , N 1.38% , P 0.24% , K 1.43% , Na 0.47% , O.C 36.32% and C/N Ratio 31.30. Results indicate fruit & vegetable markets waste are suitable for production of high quality compost in Tehran city.

Mercury is one of the most poisonous elements in the environment and causes horrible damages to living creatures so that it has attracted most attention from among heavy metal pollutants. In order to determine mercury contamination of wild fish-eating birds and understand its biological effects, the concentration of Mercury in common cormorant (Phalacrocorax carbo), collected in Fereidoonkenar region in the north of Iran, was measured. For this purpose, 14 cormorants were captured with nets from three stations in the aforementioned region in the fall and winter 2004. The mercury concentration accumulated in the fishes' muscle, feather, liver and kidney was measured by the Mercury Analyzer, Leco AMA254. The average concentration of mercury in muscles, livers, kidney, and feather was measured 2.06, 8.32, 9.25 and 4.44 mg/kg. Mercury concentration was significantly higher in the kidney and liver (p<0.01). Hg concentration in liver and muscle increased significantly with their growth from juvenile to adult (p<0.05). Also, the Mercury concentration in feather indicated a significant positive correlation with the body length (r=0.547).

The purpose of this research is to investigate characteristics of the paper made of Paulowina tomentosa and Populus deltroides. Anatomic and chemical properties of the fiber of these plant species were measured at first. According to the measurements, Paulowina tomentosa and Populus deltroides, with average fiber lengths 1,064.60 mc and 977.606 mc, respectively, are categorized as broad-leaved threes with medium fiber length. As compared to Paulowina, Populus deltriods contains more cellulose and less lignin and extractives. Cooking the paste was performed according to the NSSC process and the wood was treated with 15% sodium sulfite and 7% sodium bicarbonate based on the o.d. weight of the wood material. Regarding the optimum freeness for the NSSC process, freeness of 409 CSF was obtained for Paulowina pulp at the 7,200 rpm while this index was 415 CSF at 3,600 rpm for Populus pulp. The variable in this research was the percentage of the two components in the processed pulp (100% of each species, 90% Populus deltroides + 10% Paulowina tomentosa, 80% Populus deltroides + 20% Paulowina tomentosa, 70% Populus deltroides + 30% Paulowina tomentosa). Investigation on these paper characteristics shows that adding paulownia to pulp up to 10 percent is acceptable and it doesn't affect the strength characteristics of the paper in comparison with the paper of made exclusively of Populus pulp. On the other hand, adding 20% of Paulowina paste to the pulp up to 20% reduces strength characteristics, including burst strength, breaking length and tensile strength but doesn’t affect some other strengths such as tear strength and ring crush (RCT).

In order to adjust kiln drying conditions for hornbeam (carpinus betulus L.) lumber with 7.5 cm thickness in a way that the lumber's quality is preserved, a, drying down to the final moisture content of 8±2% was carried out through three schedules designated as T3-B1 (general acronym of FPL for Ulmus crassifolia), T3-B2 , T4-B2. The initial dry bulb temperatures were adjusted to 44, 43 & 44oC for three schedules, respectively, and the final dry bulb temperatures were set to 71, 71 & 82oC, respectively. Duncan test showed that there was no significant difference between the thicknesses of three charges, which had been commercially cut, at 99% confidence limit. The thickness of 95.4% of the lumber used in the test was measured and it was found that the thickness range is between 72 mm and 78 mm. Therefore, this research recommends adjusting the schedule at 75 mm for drying the lumber. The warp, including bow, crook and twist of lumber, were examined in all stages of drying, and analyzing the results through quality control diagrams prepared by the Excel software program showed first and third schedules fall within the favorable quality control range as compared to the second schedule. However, the third schedule produces results with more consistency relative to the first schedule. Therefore, T4-B2 (FPL) is the best schedule for drying lumber of carpinus betulus with a thickness of 75 mm. Conditioning for 24-40 hours is recommended if reducing internal stresses is required.

By carrying various cooking from sunflower stack chips using NSSC pulping process, optimum cooking at pulp yield of 43.8 % and kappa number of 82.6 was selected under cooking condition of 20 % chemical charge based on sodium oxide, cooking time of 180 min, and maximum temperature of 170 degree Celsius. The pulps were refined to obtain freeness levels of 328 ad 372 ml, CSF, by PFI mill revolutions of 150 and 500, respectively. Standard hand sheets with grammage of 127 g/m2 were made from both sunflower NSSC pulps, at three levels of 10, 20 and 30 % in admixture with hardwood NSSC pulp from Mazandaran Wood and Paper Industries (MWPI), and their physical and strength properties were measured. Statistical analysis showed that, up to 30 % of sunflower NSSC pulp with freeness of 328 ml, CSF can be blended with hardwood NSSC pulp from MWPI, to make fluting paper. It has been also shown that, up to 30 % of hardwood NSSC pulp from MWPI can be substituted by sunflower NSSC pulp at freeness level of 372 ml, CSF, if 5 % unbleached softwood kraft pulp can be used in the furnish.

This study examines the effect of indicates the effect of adding maleic anhydride polypropylene (MAPP) and polybutadiene isocyanate (PBNCO) on improving mechanical and practical properties of modified wood fiber/polypropylene composites. MAPP and PBNCO were studied with three and two parts applied, respectively. Results show that using 30 % fiber content with 3% MAPP and, 5% PBNCO improves adhesion between fibers and consequently mechanical properties of the wood fiber/polymer composites and reinforces the polymer matrix as well.

The selection of appropriate methods of utilization assessment is of great importance for evaluation of grazing management. To compare accuracy, expenses and time requirement of some utilization measurement methods for Eurotia ceratoides, an investigation was conducted in Hanna range Semirom, Isfahan. In this study, paired cages (for control) before and after grazing, height-weight measurement, ocular estimate, reference unit, plant count, stem count, production index and twig length measurement methods were used. All methods were compared by using paired cages (control test) based on Duncan multiple regression test. Analytical Hierarchy Process (AHP) was also employed to rank the methods in terms of accuracy, expenses and time requirement. Comparing methods showed that the stem count method is the most rapid and least expensive method with 0.207 and 0.215 priority rates, respectively, for time and expenses appeared to be the most proper method. However, comparing all criteria (accuracy, cost and time) concerning the methods shows that the height-weight method with the priority rate of 0.14 is the most suitable method for utilization assessment in E. ceratoides.

Determining row spacing and the proper method of harvest of Atriplex lentiformis is a research priority in the regions where shrub cultivating in deserts is possible. For this reason, a site measuring 4.5 ha in the margin of Kavir-e Siahkuh, Yazd Province, was chosen and was brought under the cultivation with the shrub. This research was carried out under the split split-plot scheme with 2, 4 and 6 meter spaces between the rows of the main treatments. Concerning the sub-treatments, the shrubs were pruned at height of 0, 20, 40, 60 cm and no pruning (control) on annual, biennial and triennial bases. Harvesting and weighing forage began in fall 1993 and continued until late 2001 according to the schedule. Results showed that there was a significant difference (P<0.10) between the cumulated forage harvested in terms of spacing treatments, and maximum yield attained in when a two meter spacing was adopted between the rows. There is no significant difference in terms of pruning regime. The difference in pruning height produces more distinguished differences toward the end of the test period. Maximum forage production was found in the treatment with height 60 cm. examining interactions of row spacing, pruning regime and pruning height, the treatment with 60 cm height and two meter spacing that underwent annual pruning yielded maximum cumulative product during the test period and was introduced as the optimum treatment in this research.

Rangelands in Iran are utilized for grazing in three ways: nomadic, semi-nomadic and rural. Each utilization type puts its effects on the rangelands. Increase in the number of livestock-raiser and their animals, decrease in the per capita area of rangelands and consequently decrease in livestock-raisers' income, on the one hand, and the exhaustion of rangelands, on the other hand, has damaged the balance between the animal, rangeland and human. As the result of this imbalance, rangelands no longer meet needs of nomadic livestock to forage. The Nomads' Organization Plan and subsequent plans for the settlement of nomads were set in motion since the last decade. These plans are aimed at encouraging nomads to stop migration and settle in certain areas in order to improve their living conditions. In this research, 13 nomadic communities organized in three groups, including spontaneous nomadic settlements, planned nomadic settlements and migrating nomads, in four zones of Fars Province, were studied. Regarding the role and importance of rangelands in providing forage for the nomads' livestock, this research was carried out in 2001 and 2002 in order to compare the livestock's dependence on the forage obtained from rangelands and from other resources in both rainy seasons and in drought, in winter and summer temporary settlements. For this reason, based on the researches conducted in the past and field studies, as well as distributing questionnaires and making interviews, required information was collected and classified and was later analyzed statistically using statistical software products. The research show a significant difference among the three groups of the nomads – spontaneously settled nomads, the nomads settled according to plans, and still-migrating nomads – in their dependence on rangelands and other resources for forage during drought and rainy seasons. Furthermore, this research proves that despite the exhaustion of rangelands, nomads are still highly dependent on rangelands for providing forage for their livestock and it seems this need has caused the persistence of traditional nomadic mode of life.

Despite their high importance, the degradation of rangelands has accelerated over the years. The livestock in excess as compared to rangelands’ grazing capacity, along with the excess number of human exploiters are (among other factors) two main causes of ongoing severe degradation. The national plan of the Balance between Livestock Number and Grazing Capacity (BLGC) is aimed at mobilizing all elements involved in policy-making, planning, execution, supervision and evaluation and is intended to eliminate the above-mentioned destructive factors. The executives of the plan along with exploiters constitute the core of the plan. Knowledge of these individuals’ participation in the plan in the recent years would pave the way for the participation of others. Having this in mind, the present research was carried out in 2001. One hundred and nineteen individuals from among the executive officials participated in the plan from 15 provinces of the state constituted the study population. There is a significantly positive correlation observed between characteristics of the Plan for Balancing Livestock with Grazing Capacity (its feasibility and ability to meet expectations) and educational programs (symbolic events, video-films, radio and television programs & extension publications). Multivariate regression results indicated that the variable "realization of expectations" puts the most effect on the extent of participation of individuals in the plan. From among the variables categorized under "individual characteristics" title, the level of education plays the most important role in encouraging individuals to be involved in the plan, and from among the variables “related to educational and xtensional methods” the variables of symbolic events and meetings with natural resources experts has the strongest effect on the participants’ share in the realization of the objectives of the Balancing Livestock with Grazing Capacity Plan.