جستجوی مقالات مرتبط با کلیدواژه « استان یزد » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

Forecasting changes in the environment has now become one of the important branches of environmental studies. One of these predictions is to investigate the possible effects of temperature changes on plant and animal species. In this research, the aim is used the land surface temperature (LST) of the MODIS satellite, separately for spring, summer, autumn and winter seasons, to investigate the changes in the average LST in the protected areas and the habitat of focal species. Focal species of the province include Panthra pardus, Acinonyx jubatus, Capra aegagrus, Ovis orientalis, Gazella subgutturosa and Gazella bennettii. In a field study, the presence points were collected between 1399 and 1402 from all over the province and protected areas, and the seasonal average of LST from 2003 to 2033 was prepared using MODIS satellite products (MYD11A1) in the Google Earth Engine system. Species habitat was modeled by using SDMs and combining regression models and machine learning. Also, the TSS threshold was used to convert the habitat desirability probability map into a binary map. Man-Kendall (MK) trend analysis test was used to analyze the trend of increasing and decreasing temperature changes at a significance level of 95%. The findings show that the decreasing changes in the earth's surface temperature have occurred in a scattered and non-continuous manner on the surface, but the increasing temperature changes are associated with more spatial continuity. The highest decrease in temperature occurred in the spring season with 15,212.69 hectares in the Iranian deer habitat, while there was no decrease in temperature in the winter season. Protected areas have experienced the least increasing and decreasing LST trends in spring.

Introduction :

Groundwater is one of the most important natural resources in the world. In the current situation, a significant part of Iran's consumption in the drinking sector is provided by underground water sources. In the last 20 years, salinization and reduction of groundwater quality have become one of the serious environmental problems around the world. This issue adds to the importance of proper management of groundwater consumption. Proper management of groundwater consumption is not possible without having sufficient knowledge of the distribution and expansion of saline and fresh groundwater and determining the processes influencing its evolution. Atmospheric precipitation and surface water, passing through different geological formations, dissolve the salts in them. Therefore, the chemical quality of underground water depends on the type of formation that passes through its empty spaces. Also, the time the water stays in the basement has an effective role in the quality and salinity of the water, because the longer the water stays in the sediments, the saltier it becomes.Groundwater in arid and semi-arid areas, especially in Yazd province, is the main and reliable source of water supply for various uses due to low rainfall and lack or absence of surface water sources. In order to check the condition of underground water, it is necessary to check the concentration and type of solutes in the water. One of the factors affecting the quality of underground water in Yazd province is the existence of destructive geological formations. Therefore, the purpose of this research is to investigate the relationship between the quality of underground water in Yazd province and the type of formations.

Yazd province, with an area of ​​about 737.54 square kilometers, is located in the central part of Iran's central plateau, between 29 degrees and 52 minutes to 33 degrees and 27 minutes north latitude and 52 degrees and 55 minutes to 56 degrees and 37 minutes east longitude. Yazd province is bordered by Semnan and Isfahan provinces from the north and west, Khorasan Razavi province from the northeast, Kerman and South Khorasan provinces from the east, Fars province from the southwest, and Kerman from the southeast. It varies from about 666 meters above the level of the open sea (Zarin sand desert near Aqda) to 4075 meters (Shirkoh peak). The present research is about investigating the impact of geological formations and units on the quality of underground water in Yazd province based on the statistics, information, and reports available in the Geological Organization using a 1:100000 geological map. In order to check the quality of underground water samples, 217 wells and aqueducts of Yazd Region Water Company's monitoring network in July 2013, the measured parameters of cations (sodium, potassium, calcium and magnesium), anions The main elements (bicarbonate, chloride and sulfate) present in water, electrical conductivity (EC), dissolved solids (TDS), sodium absorption ratio (SAR) and pH were used. To check the quality of underground water, sampling has been done in 18 regions of Yazd province. RockWorks 14, ArcGIS 10.3 and Excel software were used to draw and prepare maps.

To check the groundwater type of 217 sampled points in Yazd province, the average data of each region was used. By using the main ions, samples of the type of underground water in each region have been obtained in such a way that by separating the ions and their amount in each region and then implementing them in the Piper diagram, the type of groundwater in the region is obtained. As it is clear in Piper's diagram, the predominant type of underground water in Yazd province is chloride+sulfate and calcium+magnesium. These types cover the largest area in the plains and playas, which have limestone and marl. There is also carbonate type in the region due to the presence of granite formation heights that have better quality water. The interesting point in this graph is that none of the samples are in the fresh water category. The Piper diagram shows that the groundwater of the studied area is located in the hard and completely hard water type due to the existence of terrace deposits and new low-altitude foothill alluvial cones, which cover about 3,383,512 hectares of the entire area of ​​the region. According to the Wilcox diagram of the study area, C2S2 and C4S2 classes have the lowest and highest shares with 0.46 percent and C3S4 and C4S4 classes with 32.26 and 56.22 percent, respectively. According to the results of the Wilcox diagram of underground water in Yazd province, the water quality of the region is too salty and unsuitable for agricultural use. The results show that the high amount of salts is one of the problems of the water that is used for irrigation in this area. High concentration of salt in irrigation water can reduce the growth of crops or even prevent the growth of some crops, which results in soil decomposition and groundwater pollution. In such water, the growth of plants and their quality will be improved by increasing irrigation for washing or using intermittent water with low salinity and good drainage.

If there is a trend of pollution and over-harvesting of the underground water table in the region, in the next few years, with the increase of TDS in the region, the condition of the water in terms of drinking will become worse. The best quality of water for drinking is in the central and southwestern regions where the normal gneiss granite formation with eye grain structure is located in the mountainous area of Shirkoh, and the further we move away from the center, the worse the water quality is. The formation of these areas is of the type of terrace deposits and alluvial cones of new foothills.

To investigate the effect of biomechanical methods on increasing the vegetation in arid areas, three regions (Ashkezar, Ghahar, and Chahmatk of Ardakan) in Yazd province were selected. Statistical sites were determined within the scope of rainfall storage operations and outside it (control), and at the end of the growing season (May 2018), a survey was conducted. To do this, in each area, 100 plots of 9 square meters (3*3) at a distance of 12 meters from each other and along five transects of 300 meters, which were considered in parallel and at a distance of 100 meters from each other were placed. In each plot, canopy cover percentage and density of different species were measured. Data were compared with a t-test. The results indicate an increase in the canopy within the furrow and crescent. The canopy average in the Ashkezar and Chahmatk of Ardakan rangelands in the rain storage region increased from 2 to 3% compared to the control area. Also, an increase in the density of different species was observed in the precipitation storage area. However, sowing has been done only in the year of rainfall storage. In general, due to vegetation status and plant density by species segregation, performing remedial storage operations along with seeding using Artemisia sieberi and Salsola tomentosa species can be successful for desert rangelands with less than 100 mm of rainfall.

Mining has increased dramatically in recent years and, destroys natural resources and the environment. This study was carried out to investigate the effect of mining activities on diversity, richness, evenness and structure of vegetation cover in rangelands around copper mine of Dareh Zereshk located in Yazd province. Three sampling sites (0-200), (200-500) and (500-1000) meters far from the mine were selected for the study. Then, on each site, 3 transects of 200 m with 50 m apart, Were affected Perpendicular to the slope direction. In each plot, canopy cover percentage and density of plant species of existing species was recorded. The results of variance analysis for different indicators of species diversity, richness and evenness showed that all indicators had significant differences in the three study areas (p <0.05). So that the richness and diversity indices increased with distance from the mine and instead the evenness index was higher near the mine. Also, increasing the distance from the mine significantly increased the percentage of canopy cover of Asteraceae, Fabaceae, Poaceae, Chenopodiaceae and Lamiaceae(p <0.05). In addition, some structure of vegetation cover such as geophyte, chamophyte, hemicryptophyte, shrubs, grasses and perennials were significantly reduced near the mine. In general, the results showed that mining operations had a significant effect on the structure of vegetation in the area and reduced plant diversity. Therefore, it is necessary to pay attention to the pasture damage in the rangeland.

In recent decades, among natural disasters, the frequency of agricultural drought has been higher than other natural disasters. The best way to management of agricultural drought was to management drought-stricken society. The purpose of this study was to assess the vulnerability and spatial analysis of drought in Pishkuh watershed in Yazd province. the effective parameters in the vulnerability of agricultural drought in the region became information layers, and after weighting the layers in terms of the importance of agricultural drought vulnerability in the framework of multi-criteria decision making (MCDM) Agricultural drought in the study area was prepared. In order to control, monitoring and evaluation the final map, field studies of the study area were also used. The results showed that the highest weight of the effective parameters in drought vulnerability was related to the precipitation parameter, the value of which is equal to 0.31, and the lowest weight was related to the slope parameter with a value of 0.05. According to the obtained results, the most vulnerable agricultural droughts were related to Sanich, Darashir, Darasir, Eshkaft, Morok, etc. Geomorphologically, these areas were considered to be high and mountainous, more severe than plain areas due to the low depth of sediments, coarse-grained soil texture and aquatic resources (Qanats), mainly their vulnerability to drought, and In terms of time, they suffer more quickly, in other words, they suffer a lot of damage in the short term. While areas such as Islamia, Nasrabad, Mazrea Akhund, Hemmatabad , etc. were in a lower degree of agricultural drought damage. The results indicate that the degree of damage to agricultural drought estimated in the final map is in line with the findings of field studies. Therefore, the map of agricultural drought vulnerability has acceptable and desirable accuracy.

Droughts are one of the most common climate changes that surround many arid and semi-arid regions of the world with high intensity every few years. Based on previous studies, the SPI index is one of the most widely used indices for surveying. Meteorological droughts in the world and in Iran. It is also a critical drought that has greatly affected the arid areas, especially the Yazd province. In this research, the characteristics of drought phenomenon such as intensity and continuity at the province level were determined and analyzed. The results of drought severity analysis in Yazd province indicate that the most severe droughts occurred in the year 1998-1999. The results show that the highest drought persistence for 8 years is related to Yazd (stations of Yazd P centers of and Mohammad Abad) and then Bafgh city with duration of 7 years (stations of Qotomr, Koushk). The most frequent drought persistence in the province was 2 and 3 years old

      Plant species have different ecotypes. Identification of ecotypes with more yield operation can be useful and commercially profitable. This is the first study to investigate resin yield amount of Ferula pseudalliacea and edaphic conditions of its habitats in desert rangelands of Yazd province. For this purpose, in each region, 20 plants of the same age (5-6 years) were completely randomly selected and used according to the conventional method. Soil sampling was carried out at a depth of 0-30 cm. All data were analyzed using SPSS16 and Excel software. The results showed that bitter asafetida plants had significantly more resin yield in 7, 8, 11 (P<0.05), 9 and 10 cutting times (P<0.01) but less yield in 3 and 13 times in Chenarnaz habitat (P<0.05). The total amount of resin with 63.63 g showed a significant increase in Chenarnaz compared to Borooieh region (60.14) (P<0.01). The most amount of resin yield was observed in 9 and 10 incisions in both habitats. Totally, it is recommended to harvest bitter asafetida during ten cutting times in Yazd province rangelands for sustainable exploitation. Comparison of soil parameters showed that the sand percentage in Borooieh region and the percentages of moisture, silt, organic matter, nitrogen, phosphorus and potassium in Chenarnaz region were significantly higher (P<0.01). Increasing soil moisture storage, organic matter and essential elements of the plant caused resin yield improvement of asafetida in Chenarnaz region. In this study, acidity had a significant increase in Chenarnaz habitat, which is an effective factor in the growth and production rate of asafetida. Chenarnaz region had numerically more lime and better operation of resin yield. According to the results, bitter asafetida plants of Chenarnaz region had better resin yield operation.

Dust storm is a stochastical event that depends on several parameters, therefore, multivariate analysis of this event is really important. In this study, importance and shortage of multivariate analysis of natural disasters such as dust storm is investigated. For this purpose, Copula theory is used for bivariate analysis of dust storm. Copulas function are useful tools for multivariate frequency analysis of natural disasters. One of the main advantages of Copula theory is that there is no limit to select the type of marginal distribution. In order to perform bivariate analysis of dust storm, severe dust storm was selected based on definition of WMO from 1982 to 2014 in Yazd province. 34 dust storm events were extracted and maximum wind speed and geopotential heights were determined corresponding to stormy days. Finally, the bivariate return period was calculated based on maximum wind speed and geopotential height using the t-student Copula as the best function. Also, univariate return period of dust storm was calculated based on maximum wind speed and geopotential height, separately for comparison with bivariate return period. The results showed bivariate analysis of return period of dust storm is more accurate than univariate return period.

Due to some factors such as limitation of water resources, increasing demands in all aspects and also the impact of climate changes, the optimal management of water resources and their efficient use is an essential task. To achieve this effective management, appropriate water resources planning can be utilized. One of the basic parameters of the water management is the accurate calculation of water balance components. Present study was conducted to determine the effects of Haloxylon aphyllum artificial forest on groundwater extraction from Yazd-Ardakan aquifer. To achieve this, numbers of Haloxylon aphyllum shrubs were counted using JMicrovision software on the preprocessed Google Earth images. Then considering annual water needs of Haloxylon aphyllum- obtained from lysimetric data of previous studies- and number of Haloxylon aphyllum counted from Google Earth images, water extraction of planted forest was calculated. In next step, using GMS 8.3 and Modflow model, the aquifer balance and effective storage coefficient were obtained for calculating groundwater extraction of Haloxylon aphyllum in Yazd-Ardakan aquifer. The results showed that the 4423640 Haloxylon aphyllum existed in the Yazd-Ardakan plain and there is 56 million cubic meters of shortage in reservoir capacity. The amounts of groundwater extraction by Haloxylon aphyllum forest was estimated about 1.614 million cubic meters per year. The positive role of reforestation in relation to the dust storm damage reduction rounded and included the use of water should not be ignored. The results of the research are applicable for water resources and water use management of plantation forests.

This research aims to study temporal and spatial variations of groundwater quality of Marvast Plain to manage these recourses. For this purpose, total anion and cation, a percentage of sodium, Ca, Cl, EC, HCO3, K, Mg, Na, pH, SRA, So4, TH parameters were prepared and a statistical period of 14 years (1377_1390) was selected using the evaluation of incomplete data. Semivariograms and cross semivariograms were potted to perform geostatistcal methods and the best model was selected with regard to more R2, less RSS and a strong spatial structure, and an exponential model was fitted for most parameters. Then, interpolation methods, such as Radial Basis Function (RBF), Inverse Distance Weighting with powers of 1 and 2 (IDW), Kriging and coKriging were used. The most accurate method was selected for parameters using cross validation method and error estimation indexes such as Mean Absolute Error (MAE), Mean Bias Error (MBE) and Root Mean Square Error (RMSE). The results showed that coKriging is the best method for estimating most parameters (total anion and cation, EC, Cl, Ca, K, Mg, Na, TH). Kriging is defined as the most suitable method for estimating SRA, So4 and pH, and RBF and IDW with power 1 are the most fitted methods for a percentage of Sodium and HCO3, respectively. The results showed that the density of most parameters increases from west to east and south to north of the study area. Also, decreasing underground water quality is observed over the time.

Participation is a multi-dimensional phenomenon, heavily depending on various variables each with its own relative weight. Carried out in 2016, this study strives for critical understanding of the inhibiting parameters in public participation, as a social phenomenon, for developing of livestock drinking water in Yazd Province's rangelands. In this study, effective parameters were determined using the Delphi technique in three rounds through filling questionnaires. To elicit knowledge a group of experts consisting of 15 members of academic scholars, officials from Natural Resources and Watershed Management Office in Yazd province and some selected people from local communities were participated. Consensus among the experts on the influential parameters has been achieved after three rounds, entailing three criteria including: a least agreement of 75%, average, score of 4 out of 5, and Kruskal-Wallis statistical test. In this research, a total of 15 parameters from social, economic and climatic criteria were determined on the basis of the standpoint of the expert group. Analysis suggests that lack of inclusive rural cooperatives (weak role of NGOs), reduced rainfall and looming droughts, jointly have major impact on the social participation, by a score of 4.53 and 90.7% consensus. Meanwhile, low income and financial dependence of ranchers on the government subsidies and loans respectively by 85.3 and 82.7 percent of specialist group consensus were identified as the important economic factors. This research assists policy makers and managers of natural resources in removing the obstacles of the pathway of participation and improving public participation for livestock drinking water management in the rangelands of Yazd Province.

In order to assess drought situation in Yazd province and planning programs, zoning drought map should be prepare to reduce damage resulting from this phenomenon. For this aim, in this study after calculating standard precipitation index in time series of 6 and 12 months in 39 meteorological stations located in Yazd province, Kriging and Inverse Distance Weighted 1 to 5 were used to interpolate Standardized Precipitation Index in March 2010. Then error maps were estimated using cross-validation, root mean squared error (RMSE), mean absolute error (MAE) and coefficient between estimated and observed values (R2). The Results showed in time series of 6 and 12 months, IDW3 and 2 are more accurate, respectively. Also, the drought severity classification showed that the most percent of area belongs to low class of drought in time series of 6 and 12 months. However, with increasing time step the wet severity is decreased in the north and high drought has been changed to the moderate class in the south of the study area.

One of the major natural disasters that caused tremendous damages each year in many areas of the country is desert، especially in Yazd، Iran. Strong winds and the formation of dust storms will take place several times each year. In this study، data from meteorological stations in Yazd (thunder storms، wind magnitude (size، amount)، wind duration، visibility، fastest wind speed، average wind speed، prevailing winds and dust storms) in the period 1953-2005 were used on a monthly basis. In order to determine the most appropriate combination of neural network and input parameters (inputs) that influence the phenomenon of dust storms from Variable reduction technique of factor analysis (maximum likelihood، principal component)، principal component analysis، stepwise progressive and gamma test were used. Each of the methods presented، each with a different combination of these compounds neural network feed Forward back propagation with the algorithm of Levenberg-Marquardt have been used. The results showed that the stepwise progressive R² = 0. 87 and RMSE = 0. 04 provides the most suitable combination for a neural network. Comparison of simulated dust storm phenomenon in seasons and months in different years showed that the phenomenon of dust storm in summer and spring seasons and months of April، May، June، July، August and September are different. In comparing the neural network feed forward back propagation models with algorithm of Levenberg-Marquardt and decision tree with algorithm CART، Neural networks model with a correlation coefficient of 0. 87 and the root mean square error of 0. 04، the decision tree method with a correlation coefficient of 0. 86 and the root mean square error of 0. 06 has more carefully in order to simulate dust storm.

Rainfall erosivity is one of the most important factors in determining soil erosion. This factor is usually expressed as erosion indices that are based on rainfall characteristics.In this study, after construction of 12 runoff-sediment plots in Nir Research Station in Yazd province, the amount of runoff and sediment from each plot were monitored and measured for 12 rainfall events. Then, based on a world wide literature review, 61 rainfall erosivity indices were identified. The rainfall erosivity indices were determined for each of the storms with extracting the required parameters. In order to determining suitable rainfall erosivity indices, the correlation between the rainfall erosivity indices and soil loss values were determined. The results showed that PI602, PI302, RPI602, RPI302, RI60 with 0.730, 0.713, 0.703, 0.694 and 0.664 percent had highest correlation with soil loss amount. Generally, in the climatic condition of study area, the indices based on rainfall intensity with total amount of rainfall multiply in the square of 60 and 30 minutes rainfall are better than other indices.

Vegetation and soil characteristics are highly affected by herbivores and exploring these relationships is essential for rangeland management. This study aimed to compare the plant composition and physico-chemical soil properties under livestock (sheep and goat) and wildlife (deer) grazing regimes in Kalmand-Bahadoran plain rangelands of Yazd province. A random-systematic method was used to collect the data from 10 randomly established transects with 100¬ meters lengths and 3 plots of 2 m2 were placed on each transect. CANOCO4 software was used to analyze the collected data. According to the results, livestock and wildlife grazing were identified as the most responsible factors, describing the sites places along the first axis of Redundancy analysis (RDA) plot. The frequency of some species such as Colchicum kotschyi, Stachys inflata, Iris songarica, Lolium rigidum, Boissiera squarrosa, Noaeae mucronata, Astragalus sp. and also stone percentage increased in the sites grazed by wildlifes. On the other hand, the frequency of Echinops sp., Scorzonera sp., Launaea acantodes, Zygophyllum eurypterum, Stipa barbata, Peganum harmala, litter and bare soil percentage raised in the sites grazed by livestock. livestock and wildlife grazing did not have any significant effects on the frequency of Artemisia sieberi as a dominant species, Lactuca sp. and Cousinia sp. Soil texture, soil moisture and soil organic carbon content did not varied significantly in the two studied areas but some soil characteristics such as EC, pH, TNV and soil bulk density were higher in the sites grazed by livestock than the other site. Wildlife grazing resulted to some positive changes in soil characteristics and vegetation composition, therefore it can be concluded that similar management practices experienced in sites grazed by wildlife can enhance the range condition of other sites.

Knowledge on changes of the factors affecting range forage production is the main prerequisite for understanding the processes and optimal management of rangelands. In this research، the effects of precipitation variables، temperature and wind velocity were studied on annual forage production of some dominant range species، in Sadr-Abad steppe rangeland of Pish-kooh region، Yazd province، during 9 years. Canopy cover percentage and forage production were measured in randomly located plots along fixed transects، annually. Climatic data were collected from the nearest synoptic station. Relationship between production values and climatic variables were analyzed by correlation coefficients and stepwise regression. Results showed that، among studied climatic variables، December-March precipitation، December-April precipitation and April precipitation had the most effects on annual production of Artemisia sieberi، Iris songarica، Stipa barbata and Stipa Arabica، species respectively. While، annual production of Stachys inflata was affected، mostly، by July mean temperature and December-March precipitation. Annual production of Iris songarica and Stipa barbata affected by wind velocity in April، as well as precipitation. Results indicated that December-March precipitation could be a proper indicator to predict total range forage production.

The current research was carried out to find out the most effective environmental factors in plant species occurrence by classification and ordination methods. For this purpose, the study was conducted in Nir rangelands of Yazd province and topography, climate, soil and grazing intensity data of the region were determined. Sampling method was randomized–systematic and within each sampling unit 3-5 parallel transects with 300-500 m length, each containing 30-50 quadrates (according to vegetation variations) were established. Quadrate size was determined for each vegetation type using the minimal area; hence suitable quadrate size for different species was determined 1*2m–10*10m (2-100 m2). 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 and electrical conductivity. To analyze environmental data, classification (using TWINSPAN) and ordination (using PCA, CCA) were used. The results indicated that soil salinity, texture and available water play the main role in distribution of plant species.

Our country’s rangelands are mainly located in arid and semi-arid regions. Due to the low amount of precipitation and high rate of evapotranspiration, water stress is considered as the most crucial environmental stress for vegetation in this region. This study was conducted at Khud-e-sofla rangelands for nine years (1378- 1386) to investigate the effect of precipitation fluctuation on canopy cover and production of important plant species. For this purpose, four dominant species were selected and their canopy cover and production were monitored every year in permanent and random plots, respectively. Precipitation data were collected from the nearest synoptic station. According to the data of precipitation, cumulative rain amount was calculated at various periods. The relationship between variables of plant parameters and cumulative rain amount was analyzed by step wise regression method in SPSS 13. The results showed that plant species often reacted to the precipitation fluctuations. However, various species reacted differently to the precipitation fluctuation in terms of cover and production. The total vegetation cover as well as canopy cover of Artemisia aucheri hada negative and significant correlation with winter precipitation.Whereas, precipitation of January to April and the past year precipitation exhibited a high correlation with canopy cover of Iris songarica and Stipa barbata. The forage production was also influenced by seasonal precipitation. According to the results, total yeild and the yield of Artemisia aucheri, Lactuca orientalis, Stipa barbata could be estimated by precipitation data While, estimation of forage production through the precipitation data was not enough accurate for Iris songarica.

An optimal planning system for managing the range and maintaining its vegetation is highly influenced by the humidity and rainfall of the range. In this research، the reactions of the Cornulaca monocanta species to the fluctuation of precipitation were studied at Ebrahim-Abad in Mehriz – Yazd. For this purpose three dominant Species were selected and their canopy cover and production were monitored every year along permanent line transect in random plots. Precipitation data were collected from nearby stations. According to data of precipitation، amount of cumulative rain was determined at various periods. Relationships between variables of plant parameters and amount of cumulative rain analyzed by Back ward and stepwise regression method. The Results indicate that plants species are affected by precipitation fluctuation. The Total vegetation cover has negative and significant correlation with winter Precipitation as well as canopy cover of Cornolaca monocanta. Whereas Precipitation in January-April and winter exhibited a high correlation with canopy cover of Launaea acantodes and Artemisia sieberi. The forage production was also influenced by seasonal precipitation. According to this result، annual yield of dominant plant species and annuals production can be estimated by precipitation in winter and January-April period. In the final، Result of curve estimation show that yield and canopy cover response of Cornolaca monocanta are in two forms of power and linear، respectively.