فصلنامه تحقیقات مرتع و بیابان ایران
سال بیست و دوم شماره 2 (پیاپی 59، تابستان 1394)

In order to study thechanges of seasonal production and consumption of range species during the growing period and grazing season, SarAliAbad rangelands were selected, representing a semi-steppe area. Production was measured inside an exclosure and consumption was estimated outside the exclosure under livestock grazing during 2007-2011. Collected data were analyzed by SAS software and mean comparisons were done by Duncan's multiple range test. Results indicated that there were significant differences between production and consumption at P Festuca ovina with an average production of 161 kg/ha and an average consumption of 172 kg/ha, and Agropyron intermedium with an average production of 57 kg/ha and an average consumption of 64 kg/ha, respectively.

Drought stress is a major constraint in arid and semiarid regions, such as Iran. The application of some soil conditioners, like superabsorbent polymers, could be effective in absorbing seasonal rain and suitable source of water for plant growth during dry seasons. The purpose of this study was to investigate the efficiency of superabsorbent polymers on improvement of Calotropis procera L. seedling under drought stress. The experimental design was a factorial arrangement in randomized complete blocks with six replicates. Treatments included drought stress at three levels of 100% fc, 75% fc, 50% fc, as well as superabsorbent polymers at four levels of 0, 2, 4, 6 gr per kg of soil. Emergence percentage, emergence rate, shoot length, root length, leaf number, leaf area, shoot dry weight, root dry weight, leaf dry weight, seedling dry weight and water use efficiency were significantly affected by the interaction of drought and superabsorbent polymer. Our results indicated that under drought stress, high amounts of superabsorbent polymer had significant positive effects on shoot length, root length, leaf area, root dry weight and water use efficiency.

Curved pits have been constructed in the upper slopes of Mohammadabad-e-Chahak playa, in order to reduce runoff entrance and thereby control the playa extension. Seeds of Haloxylon persicum and Atriplex canescence have also been sown inside the pits. This research was aimed to investigate effects of pit size and pit zones on establishment rates of the cultivated or naturally growing plants. Along the line transects, 30 pits were created within the streams and 30 in flat areas. A hypothetical pit was also considered close to each pit, with the same dimensions. The number of cultivated and naturally growing plants was counted in five different zones within each pit. Plant establishment was higher for the pits created inside the streams as compared to the flat areas. The number of established A. canescence and naturally growing plants was increased by increasing the size of curved pits, however it did not affect the establishment of H. persicum seedlings. The cultivated plants showed the highest establishment in the middle of the ridge; but the highest number of naturally growing plant was found in the center of pits. The percentage of pit destruction was increased by increasing their size, nevertheless the number of broken pits was low (15%). Accordingly, we suggest, creating pits inside the streams, rather than flat areas, small pits (6-8 m2) for H. persicum but large pits (10-12 m2) for A. canescence.

The aim of this study was to determine some factors affecting dust storms phenomenon using different methods. In order to determine the best-input combination, variable reduction techniques such as factor analysis (maximum likelihood, principal component analysis), Gama test, and multivariate forward regression analysis were used. Each of these methods presented different combinations used by feedforward neural network model, with Levenberg–Marquardt algorithm and multivariate forward regression with R²=0.87 and RMSE=0.04 was selected as the best suitable combination of neural network model. In addition, monthly and seasonal data were applied by neural network using the best-input combination, and the simulation of dust storm phenomenon was done in summer and spring during the months of April, May, June, July, August and September with a higher correlation coefficient and lower mean square error, due to the good distribution of the dust storm data. The results showed that based on these methods used in this study, dominant wind speed, horizontal visibility, continuity and average of wind speed were the most important factors affecting dust storm phenomenon in Yazd province.

Allowable use is one of the most important factors in determining grazing capacity. The present study was carried out to determine the allowable use of Salsola laricina in Khoshkerood site of Saveh. In this research, four treatments including 25%, 50%, 75% harvesting and no harvesting (control) were compared during three years. The results showed that the effect of the year and interaction of different harvesting intensities and year were statistically significant at the level of one percent. In the first year of study, there was no significant difference among treatments; however, in the subsequent years, the effects of treatments were visible. So that the treatments had the most impact on the speciesin the last year. It was clear that there was not significant difference between the 25% harvesting intensity and control treatment. These treatments had the most forage production and also, there was not a significant difference between the other two treatments. The observations showed that the vitality of species in control treatment was less than that of 25% and 50% harvesting intensities, indicating that grazing can increase the plants vitality. Based on the AMMI analysis, the first interaction principal component (IPC1) was significant at the level of 1%, so that 98.2% of the sum of squares of the interaction could be expressed by IPC1. According to the biplot of the IPC1 and mean production, the lowest production rate and stability was recorded for the harvesting intensity of 75%. According to the results, it can be stated thataharvesting intensity of 25% guarantees the survival of S.laricinain this region with no negative effect on the vitality of Salsola laricina.

This study aimed to evaluate the range suitability for sheep grazing according to the Manual of Suitability for Sheep Grazing instructions in the rangelands of central Taleghan and comparison with the FAO guidelines (1991). Accordingly, the final model of range suitability was determined from combining three criteria of vegetation, water resources and soil erosion. Sampling was conducted in the key area of vegetation types through random-systematic method with four transects of 200 meters and 40 plots of one square meter and in each plot, the list of species, canopy cover percentage, and species composition as well as production were harvested and calculated. For this purpose, the results of the proposed instructions were compared with the results of the FAO model (1991) by non-parametric Wilcoxon test. Our results clearly showed that the lack of available forage, low allowable use, erosion and the formation sensitive to erosion (Marl), poor condition and negative trend in some vegetation types as well as steep and mountainous regions were among the factors, limiting range suitability for sheep grazing. The final results of sheep grazing model showed that no vegetation type was placed in S1 and N classes, and most of the vegetation types of the study area was in S2 range suitability class, so that from 25576.9 ha of the rangelands studied, 87.25% was in S2 class and 12.75% was in S3class. According to the results of comparison of the two methods for determining range suitability, no significant differences were found (P <0.01).

Increased concentration of carbon dioxide in the atmosphere is the main cause of climate change, having harmful effects for human beings. Reducing the amount of this gas by inhibiting industrial development and the use of artificial methods is not suitable due to the lack of economic justification. Therefore, taking advantage of carbon storage potential in plant tissue and soil has attracted much attention in recent decades. According to the different climatic zones in the country, studying the carbon sequestration in each of these areas should be taken into consideration. Therefore, the potential of soil carbon sequestration in the mountain rangelands of Kermanshah Province was studied in three height classes and four aspects. Then, soil samples were taken from two depths of 0-30 cm and 30-60 cm in the habitats of Astragalus gossypinus and Astragalu sparrowianus. Soil organic carbon, bulk density, electrical conductivity, pH, moisture content and soil texture were measured in both soil depths. Stepwise regression results showed that soil parameters including texture, bulk density and pH, were the most important factors, affecting soil organic carbon. Based on the results of data analysis in a completely randomized factorial design, significant differences were observed for soil carbon sequestration among height classes and aspects at 1% level of significance. According to the results of mean comparisons based on SNK test, the highest amount of carbon sequestration was observed in the third height class and north aspect. Our results clearly showed that Astragalus parrowianus had a higher potential in soil carbon sequestration as compared to Astragalus gossypinus.

In this research, the effects of important environmental variables on vegetation diversity were determined in Nodoushan-Yazd. For this purpose, 46 various land unit tracts (LUT) were studied. To collect vegetation data, the number and optimum size of sampling plots were determined using the statistical and minimal area methods, respectively. For each sampled unit, one composite soil sample was collected according to plant root depth. Soil properties included: gravel, texture, saturation percentage (S.P), calcium carbonate, pH, EC, soluble ions (Na+, Mg2+ and Ca2+) and S.A.R.The study of diversity indices was performed based on species canopy cover, the presence or absence of species and the use of three diversity indices (richness, Shannon-Wiener and Simpson). Then, the relationship between environmental variables and biodiversity indices was investigated using RDA ordination. According to the obtained results, altitude had the most impact on vegetation diversity. The species diversity indices were also significantly correlated with some of the soil variables, including Na, T.N.V, saturation percentage (S.P) and soil texture. The trend of changes in species diversity in the study area had significant correlation with the type of geological formation.

This study was aimed to determine the variation of species diversity, richness and evenness of plant species under various managements (different range conditions) in five vegetation types. After determining vegetation types, range condition was measured applying the method of society for range management (SRM). In order to assess species diversity, richness and evenness, canopy cover percentage and species density were determined along transects within plots. Species diversity was determined using Simpson index, Shannon-wiener function and Hill index(N1 and N2) and species richness was determined by Margalef, Minhinnick, Bootstrap and Jack-Knife methods and species evenness was measured using Simpson, Camargo, Smith-Wilson and Nay revised index. Mean comparison test (non-paired t-student test) was used to determine the relationship between species diversity, richness and species evenness under different conditions. The results showed that in various managements with changes in range condition, a trend of regular changes could be observed between vegetation cover and range condition. In other words, the value of estimated indices of species diversity and evenness was higher in good range condition as compared to the fair and poor range condition; however, the maximum value of species richness was related to good, fair, and poor conditions, respectively. Results of mean comparisons showed a significant difference between good and poor condition for most of the indices used in species diversity, richness and evenness, while there was no significant difference between good and moderate condition.

This research was aimed to investigate some ecological characteristics of Frankenia hirsuta in saline rangelands of Golestan Province. This region has saline soil with high underground water table, and halophytes usually grow naturally in this area. For this purpose, some factors such as soil characteristics, vegetative cover, phenology, forage quality, preference value and so forth were determined. According to the results, this species is usually distributed on silt-loam soils with an acidity of 7.7 to 7.8 and EC (Electrical Conductivity) ranged between 28.2 to 30.2 dS/m. The autumn regrowth of this species starts in October but, active vegetative growth begins at the middle of February, flowering occurs in June and seed ripening occurs in August. At vegetative growth stage, this species consists of 10.3% crude protein, which is decreased to 8.7% at flowering stage and 7.1% at seed ripening stage. In addition to the main root, this species has also lateral roots. The main root length is usually short around 5 cm but the lateral root length is about 50 cm, moving horizontally at first and then penetrates deeply. Overall, in saline rangelands of Golestan Province, this species has been distributed as patches in low lands and the places with suitable moisture and relatively less salinity. In order to protection and sustainable utilization of this species, it is suggested that the seeds of this plant be sown every few years in the prone areas. In addition, the time of enter and exit of livestock have to be chosen carefully.

Traditional and indigenous knowledge of range beneficiaries is a valuable national heritage for management programs and social development, providing opportunities to identify, prioritize and organize local resources. The introduction of this traditional knowledge among the population has a positive approach towards the ranch job, and can reinforce the strength of social structure in the country. Accordingly, in this research, it was tried to introduce the mechanisms of indigenous knowledge for the management of range allotments by the semi nomads of Damavand mountain summer rangelands. This is a qualitative research method, in this technique while doing interviews and gathering deep data, axial questions were determined regarding the use of rangeland. The methodology of the study is qualitative including interviews and data collection as well as determining central questions regarding the use of rangelands. Our results clearly showed that rangeland beneficiaries were easily able to determine range allotments, spatial distribution of livestock, herd size, sites of drinking water and so forth. They also can use all parts of a range allotment through traditional grazing systems, exclosure, and observing livestock entry to the rangeland. It seems that indigenous knowledge and occupational experience of shepherds can perform an important role in collaborative activities to achieve sustainable management and provide the success of rangeland projects.

South Khorasan province with vast rangelands with an arid and semi-arid climate and specific species is one of the most suitable areas for camel breeding. Despite the importance of camel in the province, no research has been conducted on species selection by camel as well as its relation to chemical factors of plants. Therefore this research was aimed to investigate the relationship between palatability and nutritive value of range species in south of Birjand. For this purpose, the selection of range species by camel was investigated in three phenological stages of vegetative, flowering and seeding using chronometer. For each stage, the study was conducted during three days in the morning and evening. In this technique, each camel was followed for 30 minutes during the feeding. In addition, plant samples were collected for chemical analysis. Data analysis was performed using SPSS 15 software. Results indicated that there were no significant differences between preference value and chemical composition of species. The highest values of DMD, ME and CP as well as the lowest CF, ADF and NDF were recorded for Seidlitzia rosmarinus. According to the obtained results, the effects of chemical composition on species palatability varied from one species to another one. However, these effects depend on different factors including vegetation composition, available forage, species distribution, livestock taste and so forth.

The source of sandy dunes has been the main question in desert regions. Several theories have been already presented about this question around the world. In addition, several methods have been already invented and applied to find the source of sandy dunes. In this research, the relationship between playa and sandy area in Yazd province was studied using GIS. At first, the maps of sand dunes and playa in the province as well as neighboring areas were produced. Then, the distance and direction of all sandy polygons to the nearest playa was calculated. Meanwhile, the geographic center of sandy polygons and playa polygons were identified. According to the results, around 60% of sandy polygons had a distance less than 10 kilometers to the playa, and their average distance to the nearest playa was calculated to be 12745 meter. In more than 79% of sandy dunes, the nearest playa was located in the North West. The average angle of playas to the sandy dunes was 332 degree (N), matching with the main windroses and sandroses of province. Therefore, if all sandy dunes and playas are converted to one place, we will have one sandy dune with an average area of 4717 hectares as well as a playa with an average area of 220506 hectares in the northwest of sand dune. Eventually, according to the prevailing wind direction, the hypothesis of the role of playas as the main source of sand dunes in the Yazd province is reinforced.

Due to the difficult field operations in desert regions, in order to measure wind erosion, the use of devices with a high-performance, resistant to environmental conditions and need less maintenance is required. The main objective of this research was to design, manufacture, and evaluation of EDST (Eight Directional Sand Trap)", so that it could be used in areas exposed to wind erosion and sedimentation. The device is made of two parts including the sediment catch from the soil surface to a height of 60 cm and sediment holding tanks for the eight geographical directions. According to the obtained results, the catching efficiency of this sand trap varied in different examined wind speeds (1, 2, 3, 4 and 5 ms-1);so that the most efficiency was equal to 47.3% at 4 ms-1. In addition, the device efficiency in determining the direction of sediment transport increased by increasing tunnel’s wind speed and reached to the highest value (61.8%) at 5 ms-1. The comparison of cumulative curve of sediment grading inside the sand trap and sediment source in the wind tunnel showed that the device was selective to diameter, so that the trapping of particles whose diameter was more 1 mm was done with an efficiency of 86%. However, it was inefficient in tapping the particles smaller than 1 mm.

This research was aimed to study the preference value of range species in Til Abad rangelands. To determine the preference value, timing method as well as measuring the production and consumption of species was used. According to the results of analysis of variance, significant differences were found for the study species in timing method, so that maximum consumption time was recorded for Artemisia sieberi, Poa bulbosa and annual species, respectively. The results of species utilization percentage also showed that there were significant differences among the study species. The highest consumption rate was recorded for Poa bulbosa and annual species. Artemisia sieberi, Festuca ovina and Stipa barbata had an average preference value; however, Poa bulbosa and annual species were relatively palatable. Our results clearly showed that species density and abundance and access to forage species strongly affected the preference value. Generally, in bothe methods studied, Artemisia sieberi, Poa bulbosa and annual species were more grazed as compared to other species.

This study was carried out to compare the forage quality parameters (CP, DMD and ADF) in two phenological stages between two regions in south of Fars province. The two regions were located close together, and with the exception of soil characteristics, were similar in terms of other environmental factors. One region had a saline-alkali soil (pH= 8.30, EC=15.6, SAR=6.51, ESP=%2.84.) and the other region had an alkali soil (pH= 8.53, EC=1.24, SAR=4.18, ESP=%1.12.8). The common plant species were sampled. An independent t-test was used to compare the content of ADF, CP and DMD of forage in each phenological stage between saline-alkali and alkali soils. A paired t-test was applied to compare forage quality parameters between two phenological stages in each species separately. Results showed that in both phenological stages, halophytes such as Atriplex halimus and Seidlitzia rosmarinus had a better forage quality in alkali soils. Most species were not significantly different in forage quality parameters between the two regions. In vegetative growth stage, DMD and CP content in halophytes were higher in saline-alkali as compared to alkali soils, and ADF was also higher in saline-alkali than that of alkali soils for a few halophytes such as Seidlitzia rosmarinus. In flowering stage, except for Seidlitzia rosmarinus, digestibility of species was not affected by soil chemical properties. This study showed that some species had relatively more adaptation to harsh condition, and subsequently had higher forage quality. Therefore, the manager could identify these species and use for conservation purposes.

Analysis of drought and factors affecting it using remote sensing data has a high potential to improve scientific knowledge about the properties of drought and the effects of this phenomenon on vegetation. The present study was aimed to investigate the relationship between satellite indices and the SPI index in northern rangeland of Golestan province. For this purpose, SPI index in one, three, and six month- moving averages was calculated and then zoning maps were prepared using kriging. Then, using MODIS images and the corrections, required for this type of sensor, made on the images, a vegetation map was prepared using the indices of NDVI, SAVI and VCI. In order to synchronize the climate data with satellite images, a 9 -year-old common time base was selected. Finally, in order to investigate the relationship between vegetation indices with the SPI indices correlation coefficient and linear regression were used. The results indicated a good correlation between satellite indices and SPI indices in the peak months of vegetation growth. In addition, correlation between vegetation cover indices and three and six-month moving average in non-growing season, and with a one-month moving average of SPI in growing season was higher.