IRANIAN JOURNAL OF NATURAL RESOURCES
Year:2007 | Volume:60 | Issue:1|Papers Count:33

Studying the influence of water erosion and wind erosion in the given watershed sediment yield and also the importance of estimation and comparison between water and wind erosion sedimentation yield potential and also the determining the efficiency of empirical methods such as IRIFER, S in the estimation of the amount of water and wind erosion are the objective of this research. In this study the homogeneous unit label (Ahmadi & Ekhtesasi method) is prepared and then according to the MPSIAC and IRIFER empirical methods, the amount of water and wind erosion is determined at each homogeneous unit. Furthermore, maps of land erodibility for water and wind erosion are prepared using modified MPSIAC and IRIFER, S models. Sedimentation potential was measured using the relation between sedimentation degree and the sediment production. In these researches, according to climatic and edaphic conditions of this studied region, it was found there is some inaccuracy with the factors like soil moisture and management of land use in order to estimate the wind erosion yield. If the IRIFER, S model is revised and improved it will be efficient in regions similar to the studied basin. It was also concluded that the improved MPSIAC, regarding direct measurements in the zone conducted simultaneous to this research, produces good estimates of water erosion yield. Finally, the research shows that IRIFER, S models quantitatively and quantitatively enjoys a reasonable precision. Quantitatively, the research shows wind erosion and water erosion contribute to decrease in the soil fertility by 22.6% and 77.4%, respectivley. The total sediment amount in the studied regions is 9.7 ton/ha/yr, of which 2.2 ton/ha/yr is produced by wind erosion and 7.5 ton/ha/yr by water erosion.

In this study avalanche release conditions of Se Pestan watershed (2677.2 hectares) in Fereidunshahr town, Isfahan Province, was investigated. Vast field inspections were conducted and information on the history and characteristics of avalanches were gathered from locals. Studies on geomorphology, plant cover, and geology of the region were also performed. By means of the GIS (Geographical Information System), maps on hypsometry, slopes' gradients and aspect, the convexity or concavity of slopes, geomorphology, geology, land use and vegetation cover were prepared. In order to determine high priority avalanche zones, related score tables were prepared in terms of on vulnerability to the avalanche and its probability. These tables are prepared based on 6 indicators, including topography, climate, surface soil condition and vegetation, lithology and geomorphology, snow properties and damage dimensions. These indicators have been divided into sub-indicators and scores have been attributed to avalanche zones with respect to the causes of avalanche and their role and the results have been recorded in order to allow a comparison. Tables of avalanche passes are also provided in 5 hazard classes. Combining these data and aerial photos, the map of avalanche zone for nine zones was produced with reasonable correspondence between the map and field measurement. There are four passes with very high risk and two passes with relatively high risk in this region. The correspondence between field measurements and the information provided by the map show the reasonable precision of the method. At last, in order to facilitate the use of this research by government departments, the map of avalanche hazard priority produced based on the method described above is provided. This research helps identifying and determining avalanche zones where recorded data and figures are not available.

Various limitations, including the insufficient number of hydrometric stations, difficulty in collecting hydrometric data and high cost of data and information collection, requires using hydrologic models to estimate flood hydrographs. Application of rainfall data in un-gauged areas is a feasible option owing to their acceptable accuracy. This research is aimed at examining the possibility of integrating characteristics of hyetographs and hydrographs in order to develop the flood hydrograph and recognize its characteristics in Kasilian region with an area of 66.75 sq km, based on the available rainfall data. For this purpose, 15 characteristics of the hyetograph, 11 characteristics of the hydrograph and 11 characteristics of a time index connecting hyetograph and hydrograph for 49 storms were considered. The relationships were investigated using bivariate and multivariate regressions. Results showed hydrographs may be produced based on components of hyetographs, and as well developing simplest form of hydrographs only by the duration of excess rainfall. An almost perfect hydrograph can be produced by calculating the duration and amount of excess rainfall and occurrence time of 15 minutes maximum intensity.

A debris flow is a phenomenon that usually happens in watersheds and plays an important role in sedimentation. It also creates damage. In many cases, most of experts confuse this phenomenon with flooding and for the same reason fail to take wise measures in managing and controlling it. One of the outstanding differences observed between this phenomenon and is different sedimentological behavior of these two. Finding the origin of debris flow plays a crucial role in determining its nature and developing proper methods to manage and control it. This research, focused on a debris flow happened in Tool Baneh watershed in south of Gorgan, Golestan Province, studies and analyzes the event sedimentologically. This debris flow event occurred in summer 1999 in Ziarat watershed, Golestan province, after a heavy rainfall. The debris flow originated shortly after an intense rainstorm in the upper part of watershed where runoff mobilized the debris. Debris flow event originated only from Tollbooth subwatershed. 12 sediment samples were collected from the deposits left the day after event and the grain size distribution analysis (granolometry) was performed. Field observations showed that debris flow had originated mainly from down the watershed and caused by the land slides in the valley sides of stream. For comparison of sediments of source and deposition area 7 locations in upper part of Tollbooth subwatershed (source area) were selected and 2 samples from right and left bank of the stream were collected that underwent grain size distribution analysis. Krumbine and symmetry indexes and trask coefficient were also computed for each sample.

Facts show that the level of groundwater has notably dropped in the Karaj River basin in recent ears. In the long term, this drop may ultimately reduce the quality of water resources and increase eh cost of waster extraction and cause the depletion of groundwater resources as the result of land settlement. Therefore, a solution to this problem should be found. This research examines the possibility of artificial recharge of the river in an area between Bilaghan diversion dam and grain mines near Sarhadabad in order to increase enhance the aquifer. Based on the facts and figures collected through piezometry wells over the last 30 years, it was concluded that the lever of groundwater has extremely lowered in recent years. In order to establish the existence of sufficient water for recharge, records of the years 1992-2003 were reviewed. The records show the flow of the river at the desired point is 92 million cubic meters per year. To determine the surface infiltration rate of the river bed, two representative infiltration pools were dug. The pools recorded water infiltration with a rate of 103 L/s.ha in a three-week period. Regarding the 150-hectare area of the river basin, above 1.3 million cubic meters of water may be depleted through infiltration and the same amount may be substituted through recharging. To examine the possibility of transmitting surface water to the aquifer, geological sections and texture of the underground soil layers have been evaluated, and regarding the absence of a clay layer with low penetrability and also because of the possibility of transmitting more than 2,000 cubic meters of water per day the feasibility of introducing surface water to groundwater resources was approved. To design the type of retarding structures on the river bed, two methods – balance slope and sediment movement threshold – have been compared. Since the results showed that inappreciable erosion occurs in the design conditions, therefore, the second method was selected as the appropriate alternative. Flood routing, using HEC-RAS computer software were used to design location and height of the retarding dams.

Beech (Fagus orientalis Lipsky) is one of the most important species in northern forests of Iran. This species is a main constituent of northern forests of Iran in terms of both the volume and coverage, hence the survival and protection of this plant is highly important. Therefore, a way to protect and revive this plant is to find the types that are resistant to various environmental stresses, such as late and early cold. Enzymes are the most sensitive causes of physiologic changes in the plants undergoing environmental stresses. In this research, the enzyme content of branch tips of 90 trees in (1,100 m, 1,500 m and 1,900 m) elevations was collected in order to study seasonal qualitative and quantitative changes in proxidase and catalase enzymes within seven months and the results were compared (Duncan test). Proxidase and catalase enzymes were studied quantitatively by spectrophotometry. Furthermore, the proxidase collected underwent qualitative tests based on the PAGE (polyacrylamid gel electrophoresis) method. Results showed that proxidase and catalase are more active and more isoenzyme bands are observed in the cold months as compared to warmer months. In Farvardin (March 21-April 20), catalase is quantitatively more active in higher elevations relative to lower elevations however the number of isoenzyme bands of proxidase in the trees located in lower elevations was more to combat the stress caused by late cold. In Shahrivar (August 23-September 23), the number of isoenzyme bands significantly increases in higher elevation as a means to resist early cold. This research again emphasized the role of proxidase and catalase in the face of physiological stresses, especially decrease of temperature.

A way to protect natural resources is to educate citizens in order to help them know these resources and their importance better. The first step to start such education, it is necessary to know the current level of public knowledge of the issue. The general goal of this study is to grasp public knowledge of natural resources and its importance. The focus of this study is toward the awareness of the students of state universities in Tehran about the forest and its importance. The study method is a two-stage cluster sampling in which 975 students of different faculties were randomly questioned through a questionnaire containing 50 questions with four answer choices. The students questioned divided into six groups, including medicine, technical and engineering, humanities, agriculture and natural resources, basic sciences and art. The questions covered eight different fields such as forest geography, knowledge of natural environment and botany, effect of forests on air and atmosphere pollution control, effect of forests on soil erosion prevention, forest products, forest administration and organization, forest protection and socioeconomic issues, forest management, harvesting, and conservation. Answers of the students in the six categories were analyzed and the extent of knowledge of the issue in each group was determined. The result of the study shows that the differences of knowledge between the students of natural resources and other five groups are significant, while this difference among other groups is not significant. Regarding the students' low knowledge of the issue, the study emphasizes the need to improve students' knowledge.

In this research, forest stands of the two protected and non protected areas of Arasbaran forest region are studied and qualitative factors are compared. For this purpose, the similarity of this stands were studied using aerial photographs taken in 1968 with 1: 20000 scale and similar stands were selected. Then, qualitative specifications of forest stands in 92 line samples (transect) in non-protected area with the statistical network size 150 m × 300 m size were chosen and were compared to specifications of 92 line samples (the correspondent statistical network). The two sites were compared in terms of qualitative characteristics, including percentage of species composition, percentages of height or coppice, percentages of vertical or non-vertical trees, percentages of curved and non-curved trees. Finally it is found that percentages of Carpinus and Querqus composition have significant differences in two forest stands. Also the percentages of coppice and vertical trees in these two areas showed significant differences.

In this study, the line intersect sampling method was employed in order to estimate residuals produced in northern forests. The parameters evaluated in this study were volume and weight per hectare. The results were compared based on the theory of probability, Huber formula and Smalian formula in order to find the best method. The study was carried out in three parcels with a total area of 107 hectares. 100% inventory was used to specify real indexes of the statistical population and then a linear sampling was conducted within a 100m*100m grid with transects with a length of 100 m in order to measure the volume and weight in a hectare. Based on the Tukey's method, the comparison test conducted with the real mean values and the mean values gathered in sampling showed there is no significant difference between real mean values and the mean values calculated in linear sampling based on the Huber formula. Furthermore, as regard the three methods of measurements, the linear sampling includes confidence limit. However, because of the inhomogeneity of the population and the lack of a plenty of sampling line, inventory errors in the linear sampling method is beyond the acceptable level (10%). Regarding the results, it was concluded that a linear sampling method based on the Huber formula is the best alternative to estimate the amount of residuals in forests.

Environmental factors such as water vapors affecting tree’s aerial parts. Clearly, these factors also affect the masses of air and water vapor moving above or hanging over threes. This interaction enhances cloud seeding in forest regions and encourages higher precipitation in these areas as compared to other places. Improper land use shifting (from forest to cultivation or rangeland) not only decreases soil’s permeability, moisture storage capacity and, as a result, mechanical resistance in the face of natural phenomena such as the wind, water and agricultural machinery but also reduces precipitation, which lengthens soil drought period. This study focuses on 4 treatments, including fallow, rangeland, shrub land & forest at the height of 1,700 meters in south of Gilan (Cibon forests). Based on meteorology predication and before clouds cover the sampling region, in 3 replicates the soil’s moisture weight was measured in depths of 0 ,5 , 15, 25, 35 ,50 , 75 cm. Sampling repeated after the rainfall and the moisture percentage was determined in the laboratory. and after ranfall this measurment was repeated. Simultaneously, the soil samples were measured for their specific weights by the SAS statistical software program and according to the GLM method. The result showed that when rainfall does not directly originate from clouds the impact of water and its permeability was significant by 95% and 99%. However, this trend decreases as one leaves the aggregated forest (bushes, pastures) and reduces to zero in more remote distances.

The population structure of pikeperch Sander lucioperca living in the southern waters of Caspian Sea was studied using the truss network system. Samples were collected from the main fishing areas of this species in Iranian shores of Caspian Sea (Western and Eastern shores of Gilan) and also the Anzali Wetland. Truss distance as well as eye diameter and interorbital width of 27 samples were measured. Univariate analysis (One-way ANOVA) of 13 characteristics among the samples showed significant differences with varying degrees that showed relatively high phenotypic diversity in the Sander lucioperca population in the three zones of sampling. Plotting discriminant functions 1 and 2 revealed that the pikeperch of eastern Guilan shore is highly different from the populations found in the western shore and the Anzali Wetland, while the samples from the western Guilan and the Anzali Wetland showed greater similarity. The average of correct assignment of individuals into their original samples was 82.6%.

In this research, 15 male brood stocks in three age groups of 2+, 3+ and 4+, and 8 female brood stocks were used in order to study the correlation between the spermatocrit and the period of sperm motility as a qualitative indicator, on the one hand, and the fertilization rate and the formation rate of eyed eggs, on the other hand, were used. Five brood stocks were used in each age group. Results of the research showed that correlation between spermatocrit of male brood stocks in the same age group with fertilization rate (r=0.804) and eyed egg (r =0.836) is positive and significant. Correlation between spermatocrit of male brood stocks in one age group and the duration of motility was negative and significant (r=-0.374), and correlation between duration of motility with fertilization rate (r = 0.271) and eyed egg (r = 0.031) was not significant. There was a significant difference in the average spermatocrit of various male age groups (P³0.05) while 2+ years males were the highest (32.66±0.46%) and 3+ years males were lowest (23/26±0/18%) percentage of spermatocrit in this range. 2+ years males showed lowest duration of motility (24.50±0.2 sec), and 4+ years males showed the highest time (27.40±0.14) at (P£0.03). Fertilization rate in 2+ years male were highest (87.52±1.16) and had significant difference as compared to 3+ (79.39±2.2) and 4+ (80.45±2.02) male ages (P£0.031). Eyed eggs in 2+ years male were highest (82.52±1) and had significant difference with others groups while 3+ years males (74.60± 0.8) showed lowest eyed egg rate.

Antioxidants are the agents used to prevent or retards the deterioration of the materials that tend to be oxidized during storage in refrigerators. In this study we studied the effect of citric acid on preserving the quality of Rainbow Trout in cold storage. Two samples of the fish were dipped in two citric acid solutions with different concentrations – 1.5% and 3% – of for 60 minutes. The control sample was prepared without dipping in the antioxidant. Peroxide value (PV), total volatile nitrogen (TVN), total microbial count (aerobic mesophilic microbes) and organoleptic tests were performed twice in four months. Results showed that the sample containing citric acid (C2) had the lowest peroxide value, TVN and microbial load measured 8.4 meq/1000g, 19.7 milligram percent and 1.5×103, respectively. The control sample had the highest PV, TVN and microbial load, and the organoleptic test created a more satisfactory result with the sample containing citric acid.

Effects of carbohydrate to lipid ratio at two different protein levels on the activity, growth, chemical composition of the body and the Hepatosomatic index of rainbow trout (Oncorhynchus mykiss) were investigated in this trial. For this purpose, fishes with the average weight of 60 ± 0/55g were used. The fishes grew in 1,000-L tanks filled up to 500 L of water for a period of 60 days. The experiment was conducted as a 2 × 2 factorial at two protein levels (40% and 45%) and four carbohydrates to lipid ratios (0.5, 1, 1.5 and 2). The experiments were carried out randomly in triplicate. The food quota was almost fixed and equal to 4,000 kcal/kg. The food to be daily consumed by the fishes was determined as 2% of the biomass in each tank and the fishes were fed twice a day. The weight of the biomass was measured every 14 days though biometry and growth indexes were calculated. Results showed that the increase in the protein content produces almost no significant difference among the treatments in terms of growth indexes (p³ 0.05), and this increase did not improve growth indexes (weight gain, SGR, and PER). The FCR and price index were also better at the lower protein content (40%). On the other hand, an increase in the carbohydrate to lipid ratio (increase in carbohydrate and decrease in lipid) showed no significant difference among the treatments in terms of growth indexes (p³ 0.05) but the growth improved at the ration of 0.5 in general. Results of this research shows the most favorable conditions for growth exist at lower protein content (40%) when the carbohydrate to lipid ratio is 0.5 without any negative effects on the liver.

Natural Forest Parks are complex ecosystems. The dual and simultaneous aim of conservation and tourism developments in such areas could be achieved by creating a balanced relationship between human activities and natural environment. Although evaluating ecological potential is one of the ways to provide balance in forest parks, minding people's needs and preferences is extremely important since they are real conservers of the forest parks. Sisangan is one of the most popular forest park in Iran which also known as a botanical reservoir of rare Buxus hircana, a species threatened with extinction. Inattention to preferences of users of the park no only has weakened the quality of the park as a recreation facility but also has encouraged the users to help the destruction of this invaluable natural treasure. This research is an effort to assess users' aesthetic preferences through q-sort method, and also to investigate recreational activities based on observational studies. Besides studying public preferences, the ecological potential for tourism was also determined by the use of b classification method based on type and density of plants in Sisangan forest park. Although this park has been designed with respect to the extent of recreational activities and ecological potential as well, this design has not been able to meet needs of users of the park as a recreational facility. Finally, the research presents ideas for designing concentrated and extensive recreational areas in view of popular preferences.

Unlike countries such as Chin and India, Iran has not large rivers, and is classified as a dry country in the world. Correct use of water resources based on engineering and water resources management may help planning the best method of utilization. Man should accurately recognize the accumulative negative and unpleasant effects of development along rivers and plan methods to prevent this serious risk. This paper tries to investigate the cause of pollution of Meymeh River in Ilam Province. In this research, the quality of water of the river is assessed and analyzed based on the data collected in 11 sampling stations in various seasons of 2001. The samples were analyzed based on results of BOD, DO, turbidity and pH tests. According to these results, climatic conditions, topography, geology and the soil type of the region are the factors that affect the quality of the water of Meymeh River. Although, the discharge of urban and rural sewage into the river has not yet been a serious problem this may turn into a crisis in the future. Pathologic signs of pollution are not observed but their existence within Meymeh town cannot be ignored.

The aim of the present study was to determine a method to find optimum routing considering effective environmental parameters by using GIS. For this purpose, an optimum route for a by-pass road in east of Tehran (Parchin Road) was studied. First, environmental factors, such as geology, erosion, soil type, slopes, land use, hydrography, faults and elevation were identified. Soil and land use maps were generated by employing Satellite image. Other maps were compiled and digitized. These factors were prioritized according to the pairwise comparison method. A questionnaire was designed to seek experts' opinions on the relative importance of above factors. According to the importance of the parameters, the friction and cost maps were prepared. In two scenarios, several proposed points for the start were specified and various routes were automatically plotted by means of the GIS. The routes were compared as well as maps of other effective parameters. Finally, the optimum route was determined using the Analytical Hierarchy Process. The resulted route is satisfactorily corresponds with pre-determined priorities and limitations. Results of this research showed that identifying effective parameters and using GIS facilitate determination of optimum routes by considering environmental principles.

In this research, environmental impacts of development plans on the pollution of water resources of Rasht County were studied. Two important rivers passing through Rasht are the major source of water for domestic and agricultural uses. Zarjub River that provides the major portion of water used in this country is the most polluted river in Gilan Province and even in the country. This river plays a crucial role in spreading microbial diseases directly or indirectly. The sources of pollution of the river may be classified into industrial wastewater, urban sewage and agricultural wastewater. All shops and markets introduce their waste materials into this river. This study tried to introduce the factors explaining pollution arising from industrial development in urban and rural areas. In order to measure the degree of pollution, BOD, COD, pH, NO3, TSS, DO and coliform tests were carried out. Samples were collected in 12 points (agricultural, industrial and urban areaz) were collected for analysis every three months and the results were compared to environmental standards. Result shows that pollution of the river is above allowed levels and that the river lacks any self-refining system. Ten TSS tests out of 12 (with concentration 500 mg/L), ten TDS tests, seven BOD tests, eleven COD tests, four FTU tests, three pH tests and all coliform tests revealed the fact that pollution in this river has exceeded allowed levels.

Based on mathematical programming models and the concept of linear programming, this paper uses and aimed at presenting an optimized model for establishing and developing complex pulp and paper factories with an annual production capacity of 75,000 MT. Regarding limited resources and variable cost of factors of production, including raw materials, such as various chemicals used in the process, additives and conifer fibers, labor force, potential demand, and the lead time for the production of one ton of the product from cereal straws, an optimized model is presented with the purpose to maximize annual profit. Studies show that over 1.7 million tons of cereal straw is produced annually in Mazandaran Province. If %20 of the straw produced may be used as raw material in the intended paper industries, it will be possible to found two pulp and paper factories with a production capacity of 50,000 MT of chemical pulp (soda process), 80,000 MT of writing and printing paper and 75,000 MT of neutral sulfite semi chemical pulp (NSSC process) and 108,000 MT corrugating medium (fluted paper). Newsprint production is not economic and profitable. Raw material is the most important limiting factor in determining the economically reasonable scale of production.

In this research, the effect of MAPP coupling agent on the mechanical and morphological properties of wheat straw-polypropylene composite was investigated. This composite is prepared using melt blending at 190oC . Measuring the mechanical properties of the composites indicates that MAPP improves tensile strength, tensile modulus, notched Izod impact and hardness of the composites and reduces tensile elongation at maximum load. SEM micrographs of tensile fracture surface of the composites indicate that MAPP improves interaction and adhesion between polypropylene and wheat straw particles, and due to activating effect of MAPP; the wheat straw particles are coated by polypropylene more effectively.

Different factors influence physical and mechanical properties of recycled papers. This study investigates the effects of aging and sodium hydroxide on major physical and mechanical properties of recycled papers. For this purpose, four levels of aging (0, 4, 8 and 12 months) and five levels of the sodium hydroxide applied (0, 0.5, 1, 1.5 and 2%) were selected, and three important properties– "breaking length", "fold strength" and "water absorption" – were measured. The results indicate that aging has a negative effect on the strength but increases water absorption of recycled papers. In contrast to aging, higher amounts of NaOH used in recycling process increases both breaking length and fold strength but decreases water absorption. Also, the results indicate that floatation, followed by washing screens, has a negative effect on mechanical properties but increases water absorption as compared to blank samples.

In this study, recycling of printed mechanical papers and its blending with CMP pulp from Mazandaran Wood and Paper Mill was investigated in production of printing paper. On the basis of deinking experiments, the optimum conditions were determinde as following: - Sodium hydroxide: 2% on the basis of o.d. weight of fibers- Hydrogen Peroxide: %1/5 on the basis of o.d. weight of fibers- Pulping time: 10 min.- Pulping temperature: 65ocThe results of deinking experiments showed that not only chemicals, but temperature and time of pulping directly influences the brightness of deinked pulp.Therefore,increasing temperature or time of pulping or both,increases the brightness of deinked pulp.In addition, the results of physical, optical and mechanical strength tests of handsheets made from pulp samples, indicated that recycled mechanical waste paper can be substituted with some portion of CMP in production of printing paper.The optimum combination was found at %45 CMP, %30 WCP and %25 L.F.

This research is aimed at studying the effect of acetylation on the optical behavior of the CMP pulp made of bagasse. Results show that acetylation considerably improves the brightness of the processed papers. Treatment with acetic anhydride slightly reduces the brightness of the papers bleached by hydrogen peroxide. Results of accelerated aging show that acetylation of free phenolic hydroxyl groups in lignin notably improves the stability of papers. Additionally, the reduction of pulp borohydride sodium improves brightness and other chromatic properties but does not enhance the photostability of papers, and color reversion in reduced and acetylated papers is equal to the reversion in the papers merely acetylated. The research proved in general that properties of mechanochemical pulps prepared from bagasse may be improved through acetylation and this process enhances mechanical and optical properties of the publp. Reduction treatment does not affect photoyellowing process to a considerable extent and only slightly prevents color change in bleached pulp. Reduction by borohydride sodium and subsequent acetylation has stabilizing effect as acetylation by itself has.

Knowing the compounds that provide food reserves of plants is an important factor in range management. Perceiving how these compounds are produced and in which parts of plants are stored and what their concentration is helps determining the most suitable time for grazing, as well as the frequency and duration of grazing. The objective of this study was to examine to how factors such as being the member of a certain species, the phenological stage, plant parts and growth form affect soluble carbohydrates concentration. The six species studied were Bromus tomentellus and Dactylis glomerata as grass, Frula ovina and Coronila varia as forb, Salsola rigida and Artemisia aucheri as shrob. Samples were collected from two highland ranges in Vard Avard and Gachsar regions. The samples were dried, ground and finally analyzed according to standard phenol-sulfuric acid method. The results showed statistically significant differences in soluble carbohydrate concentrations among the species in three stages of their growth. The soluble carbohydrate concentration were measured in different life forms and various plant parts including root, collar root and above ground (P<0.01). According to the results, highest soluble carbohydrate obtained from Coronilla varia in seeding stage. Among three life forms, forbs produce highest soluble carbohydrates with the concentration highest in above-ground part as compared to root and collar root.

The major portion of rangelands of our country is laid in arid and semi-arid regions. Fluctuation in precipitation year by year is an important factor that influences the vegetation cover. In dry years that a decrease is rainfall is experienced ranges are damaged and the cover and production is reduced. The decrease in forage production exerts more pressure on ranges. This study was conducted in ten years in Polour with the aim of examining the effect of decrease in precipitation on the canopy cover and production in Polour. The canopy cover and production was measured every year in permanent and random plots, respectively. Figures on precipitation were collected from nearby stations. With a considerable decrease in seasonal rainfall in first years of the study, a dry period began that continued until 2001 while 2000 was the driest year in this period. Results show that most of plant species are affected by rainfall fluctuation. The vegetation cover and production declined in dried years and a meaningful relationship between rainfall level and the amount of canopy cover of many species was observed. The total canopy cover of species in wet years was two times greater than it was in the driest year. The forage production was also influenced by fluctuation in precipitation, and the correlation between these two concerning certain species was statistically significant. However, various species reacted differently to the rainfall decline in terms of cover and production. In general, precipitation in the growth season had a greater effect on the cover and production in some species. Based on rainfall data in this period it was possible to anticipate change in plant's cover and production. Total forage production in wet year was 2.5 times greater than production in the driest year. This ratio was 2 in grasses and approximately 5 in forbs.

The purpose of current study is to investigate the cause of plant species' distribution in association with environmental factors to find the most important governing factors in the relation to vegetation cover and environmental factors (soil characteristics, slope, aspect, elevation and precipitation). Working units serving as the bases of the research were established, and after preparing maps of slope, aspect, elevation, lithology and geomorphology and combining the maps, a single working map was compiled. In order to study plant cover in each unit, random-systematic sampling was conducted in 10 plots. Regarding the species studies and distribution, the area of each unit was determined based on the minimal area method. Floristic list, canopy cover and density of species were determined in each plot, and vegetation type of each working unit was listed with respect to two dominant species. Furthermore, 5 profiles were sampled within the plots to study soil characteristics in 0-50 cm depth as the effective depth of rooting. Subsequently, the texture, percent of lime, gypsum, organic matter as well as pH, EC, SAR and ESP were measured. To study the soil and vegetation cover the Principal Components Analysis (PCA) was used through PC-ORD software program. The results showed that among environmental factors, elevation, precipitation and slope as the first set of factors determine the change in the vegetation cover by 39.29% while the second set of factors, including sand percentage, loam and ESP plays contributes to the change by 20.5%. These two sets of factors altogether explain 59.79% of vegetation cover variation in Damghan region.

This study is aimed at finding ecological similarities between plant communities in the Mahmoodabad river basin, 5 km north of Shahindezh city, located between 36o42´ to 36o51´ north latitude and 46o30´ to 36o49´ east longitude, with an area of 26,826.95 hectares. The plant communities of the region were classified based on the floristic-physionomic method and their similiarities were determined according to polar ordination (Berry and Curtis) and using Sorenson index. Physicochemical characteristics of the soil were also studies with respect to each plant community. In the course of floristic studies, 408 plant species belonging to 245 classes and 59 plant families were collected and identified. The research also identified 18 plant communities in this area. It was concluded that altitude, soil texture and biological factors were the most important factors determining change in vegetation communities.

In order to examine and evaluate the variety and process of deterioration of Agropyron elongatum seeds available at Natural Resources Gene Bank, research programs were carried out using 11 types. The 11 accessions underwent separate germinator and greenhouse experiments randomly in three replicates. The recorded traits of the Germinator test included viability, speed of germination, vigor and germination percentage (G.P.). The recorded traits of the test in glasshouse included viability, G.P., speed of germination, plant height, number of tillers and root length 40 days after planting. Significant difference was found between accessions for all of the studied traits. In addition, the reduction in viability and the weight of 1,000 seeds at the time of entering the cold storage were measured. Characteristics such as viability, speed of germination in the germinator and the greenhouse, the length of roots were statistically different that shows the variety of the accessions. There existed also a close accordance between correlation coefficients determined in the germinator under greenhouse conditions. The results of correlation coefficient showed that, Speed of germination, could be indicator of seed vigor. This result was confirmed by a step-by-step regression model. Negative correlation was found between reduction of G.P., speed of germination and seed vigor in germinator condition and G.P., speed of germination and plant root height in glasshouse condition. Therefore, seed deterioration not only reduces viability but also the speed of germination, seed vigor and the preliminary growth of the plant's root. According to this research, viability is extremely influenced by the origin of seeds. In all of the Agropyron elongatum accessions, because stored samples of each year were different from other years, therefore reduction of G.P., was highly affected by origin of accessions. It was not possible to differentiate between the effect of maintaining condition and effect of the seed origin. Therefore, it is not recommended to multiply and revive such seeds after several yeas. Preferentially, every accession should be revived individually.