Year:2008 | Volume:21 | Issue:1 (78 IN NATURAL RESOURCES)|Papers Count:29

In order to knowing, finding and using of applicable in formation in the range management and forage production farms, surveying of ecological characteristics of Poa araratica carried out. The method of studying was as following: In the first step we used the plant coverage plan and surveying of range ecosystems to prepare the habitat of this specious.Then, in the every region, with the concerning of area and plant coverage we selected about twelve sites for sampling and measuring of indices. In the each of these areas, the factors related to total canopy, species frequency and amount of forage yield measured. Also some qualitative characteristics such as root system, phenology, stem, seed quality, regeneration, preference value and chemical composition of the plants were studied. In view point of habitatat, generally these species distributed in the hilly lands, in Ardebil province, the distribution areas of species are Sabalan and Talesh mountains slopes, this plant distributed in this regions in various geographical directions and the existence of moisture is the main requirement for distribution of this species, coverage percent of these species in total plant coverage combination is 4 to 12%. The average deep of root system vary 30 centimeters and optimum level of soil Ec for this species 1< and optimum range of pH is 5 through 7, The seeds of this species are very thing and in average there are about 3.52 million of seeds in 1 kg, the production of seed by this plan is very well, and average range of generation is 60 through 79, growing start point in April is changeable, generally in 2000m above sea level the growing start point is in mid April. Completion of vegetative growth in the late of may. Full flower, ripening and seed dissemination to arrangement in the first of June, first of July and late of July. Due to having high nutritional value (approximately 14.5 percent protein) and low quantity of raw fiber (r.f) approximately 24.8- 31.1 percent in comparison with accompanying species such as Festuca ovina - Bromus tomemtelus Dactylis glomerata - Poa bulbosa etc ... this species have high preference value for animals. This plant have advantages such as easy propagation (with seed) ,adaptation to region, high regeneration, perennial growing and adequate canopy productions and resistance to unsuitable environmental factors (such as cold, freezing ,drought and overgrazing) and can be used in combination with other species in rangelands rehabilitations programmes.

Climate change is one of the most important challenges in sustainable development which has negative effect on terrestrial and aquatic ecosystems. The main agent of this phenomenon is CO2 accumulation in atmosphere. Carbon sequestration in plant biomass by inexpensive and multi-purpose methods in arid and semi arid rangelands is a suitable method of facing this phenomenon. In this study, in order to investigate the effect of floodwater irrigation on rangelands on carbon sequestration of shrub species, some parts of Gareh Bygone rangelands were selected. After determining the key area, dominant species of shrubs in both water spreading and control area were selected. In both areas, the amount of aboveground and underground biomass of species was estimated according by determining the wet weight of each organ. Moreover, the organic C of each organ of different species was determined. The result of comparing data average by independent sample t-test represents that despite of different response of studied species carbon sequestration to floodwater irrigation, carbon sequestration by dominant species shrubs in water spreading area with the average of 100.09 kg ha-1 is about twice as much as carbon sequestration of those species in control area with the average of 50.63 kg ha-1.

Gully erosion in one of the different types of soil erosion by water that initiation and advancement of it can tend to the great changes on landscape, degrades the lands and deteriorates the environment. Considering the variety and rate of different factors effecting initiation and progress of gully erosion which varies from place to place, recognition of the most important factors contributing in gulling that can lead to identify alternative solution for its prevention and control, Arab Gareh Haji watershed locating in Golestan province-Iran, where vast part of it is covered by loess depositions were selected as study area. In order to conduct the study remote sensing data (i.e. aerial photos data 1956 and 1967 together, with land sat ETM+ images dated 2002) using geographic information techniques were applied for Mapping and determining sequential changes of gullied area size. Characteristic of environmental factors were than analyzed to find out probable relations between them and rate of gully initiation and progress on loess depositions using correlation analysis method. Finally based on the results of the study, Alternative solutions were presented that seem to be effective in preventing and/or controlling gully erosion in loess covered areas. Results of the study were shown that initiation and advancement of gully erosion are function of mean annual precipitation, weather temperature, land slope class and aspect, lithology, source of land, soil type and its physical and chemical characteristics, vegetation type, land use and mean annual runoff depth of given area.Accordingly, it was fund out that land slope, and soil characteristics including soil depth, SAR, Ec, Na and TDS of soil are highly correlate to the rate of gully initiation as well as its progress (i.e. morphometeric characteristics of the gullies) thus based on the gained results, the best strategic solution for prevention and control of gully erosion in the studied area and the areas with similar environmental conditions can be prevention of surface runoff concentration and land rehabilitation together with vegetal cover management ,particularly controlling over grazing by livestocks, improper road construction and cutting trees and shrubs throughout the watershed.

Several cytogenetic investigations suggested that Mentha is a group of polyploids, with different chromosome numbers reported for each of the several species. This may cause the taxonomic confusion among the species. This study was carried out to evaluate the cytogenetic properties of 12 genotypes belonging to M.longifolia and M. spicata, collected from central regions of Iran. Several cytogenetic characteristics such as number of chromosomes, average of chromosome length and width, the largest and smallest chromosome length and width and total chromosome length and width were recorded for each of genotype. Results showed the number of chromosome in three genotype of M. longifolia were 24. Also result of chromosome numbering showed that genotypes number 1, 4 and 8 of M. spicata were diploid and genotypes number of 2, 3, 7 and 12 were triploid and genotypes number of 9 and 10 were tetraploid. Nine genotype of M. spicata representing three cytotypes including diploid, triploid, and tetraploid. Among the three genotype of M. longifolia, average length of chromosome ranged from 0.56 micron in genotype six to 0.93 microns in genotype number five. Among nine genotype of M. spicata, average length of chromosomes ranged from 0.52 micron in genotype number two to 0.88 in 8 genotype.

Determine of rangeland condition is one of the important factors which applicated for management and using of rangelands. For determination there are different methods rangeland conditions. New concept of rangeland condition is based on the premise that the most important and basic physical resources on each rangeland ecosystem is the soil. In this paper used to soil surface condition for determine of rangeland condition. For determine of rangeland function selected Shrubland sites National Golestan Park in heavily, moderate and ungrazed areas. 5 transect 100m located within areas. 10 1m2 quadrats were systematically placed along each 100m transect. Totally 150 quadrates placed in all areas for assessment soil surface properties. The result of study show that different between rangeland function analysis and 4 factors method is significant. In this research presented model for determining of rangeland condition by aspect to soil surface and vegetation properties in the moderate and heavy grazing areas.

Recognition of quality and food value of plants for provide to nutritive material of necessity for animals is important.The different factors are effective on quality and food value of paints, such as factors; refer to the different stages of phenologic growth of plant. In this study was compared quality of species Hedysarum coronarium in three stages of vegetative growth, flowering and seed ripening. For analysis plant, to collect of plant samples in three stages of growing, and was measured in laboratory. The results showed, the different stages of phenologic, were affected on quality of forage, and there were significant difference among the growth stages (at the level %1). Quality of forage at the vegetative growth stage was higher than flowering and seed ripening. The rate of crude protein at vegetive growth stage was %16.68 and at seed ripening stage was %6.98. Therefore with regard to high quality and yield, can be use of this plant at forage production programs.

One of the slope movements is landslide as natural disaster in different regions which causes human loss and economic damages. In this research, at first Gennatroodbar catchment about 5240 hectar in Ramsar city was selected. Then with use of interpretation of arial photos with scale of 1:20000 and 1:40000 related to 1373 and 1380, geological, topographic maps and field survey using GPS, were prepared as dependent variables. Also information layers including slope, lithology, distance from faults, aspect was prepared and digitized as independent variables in GIS environment integrated dependent and independent variables, landslide was calculated in each variable class and weighted in bivariate statistical and LNRF models. Finally, landslide hazard zonation map obtained with weight maps and their algebraic sum. Models evaluation was done with use of density ratio (Dr) and quality sum (Qs). Results indicated that most of the area landslide has occurred in lithological units including marl, clay and silt(90 percent), slope classes 45-70 and 15-25 (50 hectar). Also most of instabilities have occurred in north and west aspects (46.75 and 41.5 hectar), distance from faults 0-2 km (97 percent). This research indicated that quality sum in density area is 2.01, LNRF, 1.28 and information value 1.11.

For reaching the factors between the plant and physical factors in water source with different grazing areas. Galehbore mountain rangeland in Hamedan was chosen. Then 3 water sources were chosen for surveying since they had more importance from the aspect of the animal drinking and the sampling parts were defined around each water source.percentage of slope, geographic direction, height of sea level, percentage of wetness of soil, distance between water source and plants factors were calculated and finally the relation between mentioned factors in every water source were tasted step by step in another way of regression. In the end it was proven that the more distance from water source.The more effect of physical factors on plant covering factors. Slope, height and distance of water source had the most effect on the plant covering but the effect of the geographic direction was less than the other mentioned factors and the wetness of the soil did not have the remarkable effect on plant covering. Physical factors had the most important effect on the percentage of top covering. The condition of rangeland each 3water sources studied before was improved by increasing the distance from water sources.

This study was investigated to determine the effects of production variables on physical and strength properties of air-formed wood fiber / polymer composites. A combination of 9 treatments of wood fibers and coupling agents for air-forming is investigated. Physical and mechanical properties of the sample were analyzed using factorial experimental design with completely randomized and DMRT test is used to classified the averages. The influence of mechanism on mechanical properties is described. The results of this study showed that addition of 70% fibers to the polypropylene in air forming resulted in composites with higher strength and modulus of rupture and 55% fibers increased internal bonding, tensile strength and modulus, and lowered water absorption and thickness swelling. Thickness swelling and water absorption after 2 and 24 h water-soak or 2h water -boil Test were improved by addition 2% coupling agent.

Determination of forage quality of available species is one of the fundamental factors for the management rangelands.Forage quality affected by location and phonological stages. In this study we investigated forage quality of two halophyte species, Halocnemum strobilaceum and Halostachys caspica in three phonological stages (vegetation growth, flowering and seeding). For this purpose, 10 replications were randomly selected from each phonological stage in Gomishan range. In this experiment crude protein, ADF, metabolizable energy and dry matter digestibility were measured using invitro procedures.Data were analyzed using one way and Duncan tests. Results indicated that in both species forage quality in vegetation growth stage was more than flowering and seeding stages. Comparing forage of two species showed that in Halostachys caspica crude protein (21.5 p.), metabolizable energy (10.21 Mj/kg) and dry matter digestibility (71.86 p.) indices were more than Halocnemum strobilaceum while ADF (18.06 p.) was low in all stages. These result suggested that forage quality of Halostachys caspica was more than Halocnemum strobilaceum.

This research has been carried out for the purpose of providing wood-polymer composites from palownia, aspen, maple, and hornbeam species; In order for improving their physical properties and enhancing their applicability in industries. Styrene was chosen as a monomer for impregnation. In order to achieve the above mentioned goal; the specimens were first impregnated with styrene monomer which was already mixed with ethylene glycol dimetacrylate as well as benzoyl peroxide as an initiator. Full cell process with the exception of final vacuum was applied for impregnation. Impregnated specimens were then heated in order to polymerize the monomer by placing them in the oven. After the preparing wood- polymer composite, evaluation and comparison of the physical properties (specific gravity, swelling, and shrinkage) in control specimens and wood-polymer composite specimens were done. The analysis of data and results reveal the improvement of physical properties of all 4 species comparing to the (control) untreated specimens. Specific gravity increased in wood- polymer composites as follows: Palownia species 154.93, aspen species 127.75, maple species 47.73 and hornbeam 37%. Also the percentage of increase, in dimensional stability of palownia wood polymer composite was 36, aspen 33.56, maple 30.09, and hornbeam 22.90.

Iran has recently moved toward more trade liberalization in order to adapt its trade regulation by international ones. Removal of tariff from some imported goods (Le. timber) is an example of such policies. In order to estimate the benefits from tariff removal of imported timber a two country trade liberalization model was adopted. Three potential effects were specified from the trade liberalization i.e., tariff removal on timber.Three potential effects are (1) the deadweight gain, (2) the labor displacement costs, and (3) the reduction in social costs associated with forest destruction. To estimate the monetary values of these effects the usual mathematical logics used in micro and labor economics was utilized. Some data were collected from Bureau of Census and some from libraries, local governments, as well as through questioner. Cost-Benefit analysis was used to estimate the social benefits and costs. The estimated social benefits and costs are 1018165 milion Rials, and 326.015 milion Rials. The value for Benefit-Cost ratio was 2.12, which suggests removal of tariff from timber imported to Iran.

Ocimum basilicum L. is belonging to the lamiaceae family which is cultivated as a culinary, industrial and medicinal plants in some countries from thousands years ago. The seeds of this plant are rich in poly un-saturated fattyacids (PUFA) and produced a large amount of mucilage. The oil of seeds were extracted separately and converted to fatty acids methyl esters, and composition of fattyacids in seed oils was determined by Gas Chromatography. The results show that the highest amount of total fat between (AW.L.P.), (28.98 % of dw) in Ardabil (L.P.) and lowest (17.25 % of dw) in AG.2 (W.P.). The highest amount of palmitic acid is between (A.W.L.P.), (34.81 mol%) in Kermanshah (L.P.) and lowest (2.05 mol%) is in Kerman (L.P.). The highest amount of stearic acid is between (AW.L.P.), (7.56 mol%) in Ahvaz (L.P.) and lowest (1.42 mol%) in Ardabil (W.P.).The highest amount of oleic acid between (A.W.L.P.), (22.81 mol%) in Ghom (L.P.) and lowest (11.10 mol%) in AG.2 (W.P.). The highest amount of linoleic acid between (AW.L.P.), (25.60 mol%) in A.G.1 (L.P.) and lowest (15.55 mol%) in Kermanshah (L.P.). The highest amount of linolenic acid between (AW.L.P.), (53.89 mol%) in AG.1 (W.P.) and lowest (28.08 mol%) in Kermanshah (L.P.). The results also definite clearly that the seeds of O. basilicum L. populations have large amount of un-saturated fatty acids, mucilage (that formed supriour outer layer)and they have a few amount of saturated fatty acids.

In this research the effects of acetylation and press temperature on mechanical properties of medium density fiberboard (MDF) were investigated. Sample boards were made from acetylated poplar fibers, which were treated with different weight percent gains (WPGs of 0, 2.22, 15.97, and 19.08%) at two press temperatures (170 & 185 oC). The results were analyzed based on a complete randomized design (CRD) under a factorial experiment with two factors (WPG & press temperature). Results showed that the acetylation increased MOR and MOE in MDF. The MOR and MOE properties were determined as 17.80MPa and 2184.17MPa in the acetylated boards (19.08% WPG) and 17.48MPa and 1793.5MPa. in untreated boards respectively. Internal bond strength (IB) was higher in acetylated boards than in controls. The IB in the boards, which were made at 185oc press temperature, was determined as 0.44MPa in the acetylated MDF with the highest WPG (19.08%) and 0.29MPa in the control boards.

A usual method for river bank protection is using gabion groin structures. If this permeable structure is designed and constructed appropriately, it will control bank erosion and reclaims flood plain areas. Since there are some uncertainties in the determination of length, space and shape of gabion groins, this experimental project was performed. In this investigation a laboratory movable bed flume with 17m length, 1.5m width and 0.8m depth was used to study local scour around the head of unsubmerged gabion groins. Groins with two different shapes (L shape and straight groins) were constructed perpendicular to the flume's wall. Two different lengths of groin, 15 and 22.5 centimeter (10 and 15 percent of width of flume) resulting in two contraction ratios (20% and 30%), four different spaces between successive groins (resulting in four ratios of space to length, SIL) and three different discharges with a constant bed material and slope were used in the experiments. Based on the experimental results, and using the dimensional analysis technique, a dimensionless relationship was derived for estimating local scour around the head of gabion groins.

Dead wood is considered important in forest conservation. In this research, diversity of fungal and bryophyte communities occurring in dead beech trees were analyzed in mixed beech forest in north of Iran. The aim of this study was to analyze fungal and bryophyte communities occurring in dead beech trees. Altogether, 205 dead beech trees were investigated in this research. All dead trees (downed logs and snags) were measured. Results showed that, bryophyte communities was covered different in two general directions. In slopes with northern general direction, bryophytes communities cover was higher than another directions. Effect of dead wood size, decay stage (quality of dead wood) and species were also analyzed. Results showed that, there is no significant difference between bryophyte communities and them. Study diversity of dead wood inhabiting macro fungi showed that, there is significant difference between decay stage (quality of dead wood) and dead wood size and diversity of macro fungi as well. Meanwhile, macro-fungi were identified in recent research. According to the results derived from this research, most of macro-fungi belonged to Ascomycetyes and Basidiomycetes inhabited most of them on downed logs. It is concluded that, in this forest type fine woody debris is important for diversity of wood-inhabiting fungi, especially ascomycetes. However, coarse woody debris must also be provided to insure the occurrence of many species of basidiomycetes.

Mycorrhiza is a mutualistic relationship between plant roots and fungal hyphae. Mycorrhizal associations significantly contribute to the ecological sustenance of the stressful environments such as arid and saline habitats of Mouteh region, Iran. Mouteh Wildlife Refuge, a 220000 ha reserve, is located in the northwest of Isfahan province and south of the Markazi province. Climate of the region is arid to semi- arid with hot Summers. Nowadays, management of plant-microbe symbioses such as Vesicular-Arbuscular Mycorrhiza (VAM) is considered for restoration of disturbed ecosystems and sustenance of natural ecosystems. In this investigation, we have studied occurrence of VAM in the rhizosphere of major medicinal plant species in Mouteh. Eight sampling stations were selected. Plant and soil samples were collected from 32 plots (10x10 m) during Fall and Spring of 2003. Soil and root samples from the top 30 cm were collected and relevant ecological data were recorded. Samples were transferred to the laboratory in proper conditions and were stored properly. Soil was sieved through 720, 420, 250.170, 106 & 38 mesh screens to remove large pieces.Root pieces were isolated and air-dried. The soil was analyzed chemically, physically and biologically in the lab. Some root pieces were used for preparing longitudinal sections manually and were stained with lacto phenol cotton blue. Soil samples were used to isolate mycorrhizal spores and sporocarps by sucrose density centrifugation method. Plant and mycorrhizal species were identified taking advantage of their macroscopic and microscopic characteristics and using reliable flora and fungal keys, respectively. Results of this study showed that there were 315 vascular plant species belonging to 209 genera and 55 families from which 50 species were medicinal plants. Legominosae, Compositae, Cruciferae and Poaceae have the most number of medicinal species. Dominant VA mycorrhizal species was Glomus geosporum. Presence of mycorrhizal associations in the medicinal plant communities characterizes the importance of such symbiotic relationship in the sustainable exploitation of plant resources.

Physiological reaction of different Eucalyptus species to drought stress can help to recognize effective mechanisms in drought stress and choose the best species for planting in dryland of Iran. This study was carried out with polyethylene glycol 6000 as diminutional osmosis with different drought stress treatments: 0, -0.1, -0.3, -0.6 and -1.2 MPa on established seedling in hydroponic culture in greenhouse. Factorial experiment, based on a completely randomized block design with three replications was tested on Eucalyptus camaldulensis, E. microtheca, E. meliodora and E. viminalis. Sampling were carried out from stamen leaves of different treatments and pigments concentrate (total chlorophyle, chlorophyle a, b and carotene), soluble sugar, prolin and growth parameters included biomass, leaf area, relative water content (RWC), water saturation different (WSD), specific leaf area (SLA), leaf water content per unit leaf area (LWCA) were calculated. Increased drought stress led to increase in prolin, soluble sugar and decrease in pigments and growth parameters at four species. Prolin and soluble sugar have important plane in osmosis regulation and osmosis protection so increase in content of these substance led tolerance of plant again osmosis stress. Decrease in pigments is because of decomposition enzymes activity.E. microtheca was the most tolerant species to drought stress, although had the highest quantity of prolin, soluble sugar, pigments, biomass, LWCA and RWC.

Certain ration exist between hydrologic events such as flood flows with watershed physical and climatic factors.Understanding flood generation mechanisms and the influence of morphologic and climatic properties on such mechanisms is very important in hydrologic engineering. In this paper, variation of flood peak discharges of different return periods were studied through multivariate regression models and flood index approach. Physiographic factors such as area and slope were extracted on the basis of digital elevation model (DEM). Annual rainfall raster map was prepared by applying interpolation methods on point rainfall data. The slopes were classified into three classes of 10-25%, 25-35% and 35-45% whereas rainfall was grouped into less than and more than 800 mm. The results showed that flood curves against area in 35-45% slope and rainfall less than 800 mm has a rising and falling portion. The peak on the curve occurs around 400-500 Km2 area. This implies that in large watersheds which receive lower rainfall, the runoff coefficient and specific discharge decreases due to channel transmission losses.

This paper was conducted to investigate the physical properties of compression wood, normal wood, and opposite wood of spruce (Picae ahies).In the case of stand moisture content, there was no significant difference between the normal wood and compression wood, whereas the opposite wood was significantly different from the woods. The highest and the least stand moisture content values were observed in the compression wood (~45%) and opposite wood (~118%), respectively. The green and dry densities of the compression wood were higher than those of the other woods. There was no significant difference in the water absorption content of the normal wood (109%) and opposite wood (112.5%), whereas water absorption content of the compression wood (53.2%) was lower than that of the woods. The results also indicated that the maximum longitudinal shrinkage and swelling values of the compression wood (~3%) were higher than those of the normal and opposite woods (about 0%). In contrast, maximum radial and tangential swelling and shrinkage values of the normal wood and opposite wood were higher than those of the compression wood. Compression wood had lower maximum volumetric shrinkage and swelling compared to the other woods. Based on the findings of this study, in the same relative humidity and temperature conditions, compression wood had lower equilibrium moisture content in comparison with the normal and opposite woods.

The aim of the study was to investigate Q. castaneifolia seedlings growth and development at different irrigation treatments. For this purpose a trial under completely randomized design using four irrigation periods [0 (control or rainfed), 2, 4 and 6 days] was conducted on a sandy soil at coastal part of the Caspian region of Iran (Noor city). The results at the end of first growing season revealed that the seedlings under rainfed condition obtained least survival, collar diameter, leaf area, length and number of nodes at 2nd growth flush. However, there was not significance differences among treatments in root length, stem length, length and number of nodes at first growth flush. All characteristics measured did not significantly differ at three irrigation regimes (2, 4 and 6 days). If seedling production of Q. castaneifolia with high growth is an aim, it is suggested to irrigate the seedlings at 6-day period (instead of 2- and 4-day periods) and to maintain them under shade.

In order to evaluate light extinction coefficient and radiation use efficiency of Kochia scoparia in response to saline stress, a study was performed at Birjand, South Khorasan, using three levels of salinity in irrigation water (1.5, 8.6 and 28.2 dSm-1) with three replications. Several measurements were conducted during growth season to calculate radiation fraction passed through plant canopy, and also leaf area index (LAI) and total dry matter (TDM). Light extinction coefficient calculated with correcting fraction of plant light absorption for whole day, and using dry matter accumulation, radiation use efficiency obtained in each different salinity level. The results showed that light extinction coefficient of Kochia was equal to 0.59 for solar noon and 0.75 for whole day. The radiation absorption of kochia rose as LAI increased, and 95% of radiation was absorbed at LAI equal to 4 to 5. LAI and total dry matter accumulation were highest in moderate salinity level. In general, increase in salinity caused a delay in early season development, and accelerated plant maturity at late season. This caused plant canopies at the highest salinity reached to maximum light absorption later in growth season. Increase of salinity from 1.5 to 8.6 dSm-1 was responsible for little increase in RUE from 2.4 to 2.5 g per MJ absorbed PAR; however, it reduced with further increase in salinity. Thus, it seems that moderate salinity levels stimulate growth and dry matter accumulation of kochia and cause kochia canopy convert the absorbed radiation to dry matter more effectively.

The objective of this study was to investigate the utilization of grape tree pruning in middle layer of particleboard with poplar wood as surface layer. Experimental boards were produced using of 80, 70, 60 and 50% grape and particles in middle layer and 20, 30, 40 and 50% of poplar wood particles in surface layer, resin content (UP) at 10 and 12 percent. 24 boards were produced and physical & mechanical properties of the boards were measure and analyzed. The results indicated modulus of rupture (MOR) and modulus of elasticity (MOE) of boards increased with increasing resin content and poplar wood particles significantly. MOR and MOE of boards produced with 12% resin content and 50% grape particle with 50% of poplar wood particles achieved DIN standard requirements. The results indicated that the internal bond (IE) of boards with increasing resin content consumption and increasing of poplar wood particles were modified and the highest of IE observed in boards produced with 12% resin content consumption and use of 50 and 60% grape wood particles. In order to the lowest of thickness swelling (T.S) of boards observed in same conditions. The results of this study showed that over than 50 percent of wood materials that utilized in particleboard production, can be obtained from grape pruning residues and with apply of their in middle layer of particleboards can be produced particleboards in standard levels.

The current research was carried out to find the most effective environmental factors in plant species diversity. For this purpose, study was conducted in Poshtkouh rangelands of Yazd province. Sampling was done in homogeneous units, which these units resulted from overlaying of hypsometry, aspect, slope, geology and vegetation maps. Within each unit 3-5 parallel transects with 300-500 length, each containing 30-50 quadrates (according to vegetation variations) were established. Quadrate size was determined for each vegetation type using the minimal area method. Soil samples were taken from 0-30 and 30-80 cm in starting and ending points of each transect. Measured soil properties included gravel, texture, available moisture, saturation moisture, organic matter, lime, gypsum, pH, electrical conductivity and soluble ions (Na+, K+, Mg2+, Ca2+, Cl-, CO2-3, HCO-3 and SO2-4). To determine the most environmental effective factors on plant diversity, PCA method was applied. The results indicated that soil salinity, texture and available water play the main role in plant species diversity.