فصلنامه تحقیقات مرتع و بیابان ایران
سال بیستم شماره 2 (پیاپی 51، تابستان 1392)

Nowadays، using GIS and satellite images has a special place in the studies of natural resources and environment. Comparison of the images of a specified time period can show the trends in each region. Sistan region in southeastern Iran has witnessed several periods of drought over the past century، and droughts between 1999 and 2006 are considered as the most severe drought over the past 600 years، having many environmental، economic and social impacts. In this study، vegetation changes in Sistan were examined by Weighted Difference Vegetation Index (WDVI) using Landsat TM images of 1998، corresponding to the time before drought and also ETM+ Images of 2002 during the drought. Results showed that the area of vegetation in Sistan reduced from 101 thousand hectares in 1998 to 24 thousand hectares in 2002، mainly due to the loss of arable land and removal of the cultivation. Vegetation restoration was limited to the areas such as Chah Nimeh، Niatak، Qurqory، and ungrazed rangelands of Lorge-bagh as man-made forests and protected areas.

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.

In order to maintain the nutritional status of livestock and achieve optimum performance of livestock on rangeland، range forage must be able to provide the minimum requirement of grazing animal at various phenological stages. However، to be aware and getting informed of whether the rangeland forage does have such a potential or not، it is necessary to provide a framework on the basis of scientific principles to classify the forage quality index. Moreover، this framework must be simple in terms of functionality and applicability to be used by the specialists. Until now، such a framework has not been provided for range forage. Therefore، in the current paper، not only was the information of forage quality index of species in rangeland types of Taleghan provided، but also the desirable forage quality of species was classified. The species having more than 7 % crude protein (CP) were very desirable; the ones having less than 5 % crude protein were considered undesirable and if the crude protein of species were between 5 and 7 %، they would be desirable. The species having more than 60 % dry matter digestibility (DMD) were very desirable; the species having less than 40 % dry matter digestibility were undesirable and if the dry matter digestibility of species were between 40 and 60 %، they would be desirable. The species having more than 8 Mj/Kg DM metabolisable energy (ME) were very desirable; the species having less than 5 Mj/Kg DM metabolisable energy were undesirable and if the metabolisable energy of species were between 5 and 8 Mj/Kg DM، they would be considered desirable. The values of 7% crude protein (CP)، 50% dry matter digestibility (DMD) and 8 Mj/Kg metabolisable energy (ME) were considered as the critical levels for maintenance requirement of an animal unit (non-pregnant and dry sheep with a mean weight of 50 kg). The daily requirement (dry forage) of grazing animal unit equivalent (Fashandi breed sheep with the weight of 60. 7 Kg) in rangeland types varied between 1. 5 and 2. 4 Kg per day when the forage quality was desirable. This value was less than 1. 5 Kg when the forage quality was very desirable while it reached to 2. 4 Kg when the forage quality was undesirable. Daily requirement of animal unit equivalent in rangelands of Taleghan in phenological stages of vegetative stage، flowering and seeding stage were 1. 3، 1. 6 and 1. 9 Kg، respectively that the minimum and maximum values were recorded for vegetative and seeding stage، respectively. Results، discussion and the presented framework of classification in this paper are regarded as the fundamental information for management of animal and the rangeland in Taleghan and similar habitats in Iran، being able to provide a part of information for methods of determining the range condition، range trend and grazing capacity.

To study the nutritional value of important range species in steppe rangelands of Yazd، seven important species for livestock grazing including Stipa arabica، Lactuca orientalis، Poa bulbosa، Tragopogon jezdianuse، Eurotia ceratoides، Artemisia sieberi، Astragalus microphysa were selected as dominant species in the vegetation type of the region. In three periods of grazing season (Mid-May، late July and early August)، samples were collected with 3 to 5 replications and forage quality indices were measured by AOAC method. According to the results، forage quality indices including Crude Protein (CP)، Gross Energy (GE)، Dry Matter Digestibility (DMD)، Metabolism Energy (ME)، Digestible Energy (DE) and Total Digestive Nutrient (TDN) decreased with the progress of growth stages. In contrast، Crude Fiber (CF) and Acid detergent Fiber (ADF) increased. In general، most of the estimated factors had significant difference in three periods of grazing season. There was no significant difference among the species in terms of CP، while CF and GE differed significantly. Therefore، in the early grazing season، coinciding with vegetative growth stage، forage quality is better. Grazing at this time will have the best livestock performance which should be together with proper management to achieve sustainable production in rangeland.

Knowledge of the types of land cover and human activities in different regions is of particular importance as basic information for regional planning. Because of the special characteristics، remote sensing techniques are of great importance. In the present study، the ETM + satellite data of Kashan related to 10 July 2002 was used. Image enhancement was performed using enhanced contrast، color composite images، principal component analysis، and digital elevation model. To determine the best combination band for classification and color composite images، OIF and the correlations between bands were used. Monitoring method was used for classifying the data. Ground truth map was prepared by sampling and field surveys. After classifying، land cover map was obtained with an accuracy of 82. 45% in different classes. The results showed that the highest and lowest level of land use classes was related to alluvial fan with 29. 33% and puffy salty lands with 0. 11%، respectively. In this study، to detect the vegetation، vegetation indices including NDVI، TSAVI، RVI، DVI، SARVI and SAVI were used. The correlation coefficients among the indices showed that the highest correlation coefficient (Re = 0. 99) was related to NDVI; therefore، vegetation condition was assessed using NDVI index. Results indicated that the type and level of different land uses could be determined using satellite data by spending less time and money on a large scale with a high precision in a particular year or in different years.

To determine the effects of furrow practices on carbon sequestration and nitrogen fixation in Artemisa sieber shrublands، the areas under furrow and surrounding areas without furrow practices were identified in vegetative regions of Eyvan-key، Sorkheh and Ahovan growth areas of Semnan province. Random –systematic sampling was used in 30-40 plots of 1 square meter، along 3-4 transects of 100 m length. In each plot، canopy cover percentage، density، length، width and height، litter، above ground and underground biomass were measured. Soil sampling was carried out to a depth of 0-100 cm (average depth of root development). In laboratory for each plant، organic carbon، nitrogen، dry weight of above ground and underground and total weight were measured. Soil characteristics including bulk density، organic carbon and nitrogen were also measured. The effect of furrow on C and N storages in different parts of the ecosystem was compared by independent t-Student''s test. Results showed that in Eyvanekey region furrow increased carbon and nitrogen storage of ecosystem (32% and 37%، respectively). But in Sorkheh and Ahovan، it had no effect on carbon and nitrogen storage of ecosystem because of the project location، vegetation and soil condition. According to the different effects of furrow practices on C and N storages of Artemisia sieberi shrublands in different areas، normative location should take priority for projects like this. Doing such projects in the appropriate areas has significant effect on increasing carbon sequestration potential in ecosystems.

In order to investigate the variation and relationships among seed yield and its components under irrigation and dryland farming conditions، 12 populations of Festuca ovina were studied using a RCB design with three replications in Kheirabad agricultural research station in Zanjan province، Iran. Seed and forage yield and morphological traits were recorded and analyzed. There was significant variation in all traits in two farming conditions. The annual average values of seed and forage yield in irrigated condition were 215 and 2161 Kg/ha and were higher than 121 and 997 Kg/ha under rainfed conditions. The populations 3، 9 and 5 with average values of 208-227 Kg/ha seed production and populations 3، 4 and 11 with average of 1805-2172 Kg/ha forage yield had higher production for seed and forage yield in both farming conditions. According to results، the population 3، selected from Alborz rangelands was recommended for pasture and rangeland rehabilitation of Zanjan province. DM yield was negatively correlated with panicle emergence date and positively correlated with plant height، panicle number، panicle length، and panicle weight. Under irrigated conditions، the relationships among seed yield with all traits were positive and significant except panicle emergence date. Based on principal components analysis، the first three independent components with 55، 18 and 13% explained 86% of the total variation. Based on cluster analysis، all populations were placed in 3 groups. Finally، all genotypes in cluster 3 with higher values for seed and forage yield than two other clusters are recommended for use in breeding programs to improve synthetic varieties.

Rangelands are the largest of the earth''s natural resources that the use of them with proper management can be affordable in terms of economic and agricultural. Due to the successful results of cultivation of some grasses including Bromus tomentellus in Gharabagh of West Azerbaidjan، the determination of allowable use for Bromus tomentellus can be useful in conservation and proper utilization of the mentioned species as well as ensuring its survival. Treatments in each block were four grazing intensities of 25، 50، and 75% and control (no harvest). In each treatment، 10 individuals of species were considered as replications. Data were analyzed in a split plot in time for four years (2007-2010) by SAS & IRRISTAT software. Results showed that the effect of year، different harvesting intensities and interactions between year and different harvesting intensities on forage production and vitality of Bromus tomentellus was significant at 1% level of probability. No significant difference was found between control treatment and grazing intensity of 25 percent as well as 25 and 50 percent. With increasing harvesting intensity to 50 and 75 percent، average rate of production decreased significantly compared to control. Average production and vitality showed a downward trend during 2007-2010 due to the severe reduction of average production and vitality at 75% harvesting intensity. Other treatments including control، 25، and 50 percent، showed almost similar trend during the four years. Based on AMMI analysis، first interaction principle component (IPC1) was significant at 1% level of probability and explained 99. 19% of interaction sum of squares. According to the biplot of first interaction principle component and average production، the least production and stability was obtained at 75% harvesting intensity while maximum stability was recorded for 50% harvesting intensity. According to the results، a harvesting intensity of 50% is recommended for Bromus tomentellus in the region so that health and vitality of this species is preserved during the harvesting years.

This study aimed to investigate the variation of soil seed bank density، richness and its similarity with above-ground vegetation in different distances from water point in Kahnuj rangelands. Soil sampling was carried out after seed dispersion within two soil depths (0-5 and 5-10 cm) around three water points at intervals of 0، 20، 50، 100، 120، 150، 200 and 300 m to water points. Soil samples were spread in the green house after cold treatment. Seedling was identified after germination، counted and removed once each 10 days. Above-ground vegetation composition was determined during growing season to estimate the similarity between soil seed bank and vegetation. General Linear Model was done to compare soil seed bank characteristics between different distances to water points and depths. Results showed that the soil seed density was significantly different between the distances، with the lowest at nearest and the highest at furthest distances to water points. In spite of absence of the plant cover at nearest distance، some seeds germinated from soil. Although، the richness was significantly different between the distances، there was no any specific trend in seed richness with distance gradient. Similarity between soil seed bank and above ground vegetation was increased with increasing the distance-to-water points. In overall، the highest seed density was related to annual species. Despite the presence of tree and shrub species in the ground vegetation covers، they were not presented in the soil seed bank.

Variations in reproductive characteristics of plant communities result in a shift in composition and structure of plant communities. The main goal of this study was to investigate the variation in reproductive characteristics of plant communities caused by livestock grazing in steppe rangelands and simultaneously to examine whether this shift in plant community composition is accompanied with variation in reproductive traits. For this purpose، random-systematic method was used to estimate canopy cover، height، number of spike and spikelet، number of flower and floret and number of seeds in plots، randomly established along three 100-m transects in three grazing treatments including long and short term grazing and exclosure. Detrended Correspondence Analysis (DCA in PC-Ord4. 2) and analysis of variance (with multiple comparison; Tukey test) were used to reveal the shifts in composition and reproductive characteristics of plant community. Results showed that there were differences in plot distribution in ordination diagrams of three grazing treatments and these areas could be distinguished from each other in terms of plant community composition and reproductive characteristics such as number of seeds، floret، and number of spikelet in graminoids، flower and spike. Moreover، seed production of different classes of plant palatability was significantly different among grazing treatments. Results indicated that shift in plant community composition، resulted from livestock grazing، were accompanied with a shift in reproductive characteristics.

In this research project، some vegetative and generative taints were evaluated in 5 populations of Festuca ovina including: Kelack، Sirachal، Gorgan Kordestan، Zanjan، in greenhouse conditions. The seed samples of five populations were sown on the pots with temperatures (20±5) °C for day and (5-12) °C for night time. For cold treatment، some pots were transferred at 4°C on 15th of seedling growth stage for two weeks and again were returned to normal conditions of greenhouse. After a while، those pots were placed outdoor to complete the flowering stage. Vegetative and generative traits including: percent and speed of emergence، seedling length، vigor index، tiller number and leaf area، plant height، peduncle length، panicle length، panicle number and flag leaf length، seed yield، fresh and dry weigh were calculated for five populations. Results showed that the means of percent and speed of emergence، seedling length، vigor index، tiller number and leaf area in populations of Kelak، Sirachal، Goragan and Kordestan were increased by cold treatment compared to control. The mean values of generative traits in 5 populations by cold treatment were higher than that of control. Results also showed that populations subjected to cold treatment flowered earlier due to having lower values of growth degree days (GDD). Therefore، the emergence of flower in five populations was earlier with cold treatment than that of control. The mean of some generative traits including plant height، number of panicle، seed yield، fresh and dry weight were increased by cold treatment but this increasing was more for Kordestan and Gorgan than other populations.

While grazing in rangelands، the livestock select the species and some species are preferred over others. In this study، preference value of the species was investigated during 2007 to 2010 at Binalood rangelands in Khorasan Razavi province. This research was performed using timing method and filming the livestock grazing for three times per year during the grazing season. The results of grazing time percentage for each species were analyzed by SAS software. Among the rangeland species، those grazed by sheep at least two years were analyzed. Results indicated that Agropayron intermedium was more grazed compared to other species. Scariola orientalis، Convolvulus arvensis، the flowers of Onobrychis cornata and Eremurus spectabilis were highly considered by livestock and allocated most of the grazing time followed by Agropayron intermedium. Also، the percentage and degree of palatability of some species showed significant differences at various stages of filming and during the study years، so that most grasses had a greater palatability in vegetative growth stage، which declined in the later stages. In contrast، livestock preference for some species such as Iris songarica and Verbascum songaricum increased during the final stages of growth.

Some of the ecological and morphological characteristics of Festuca ovina in southeastern rangelands of Sabalan within the elevation of 1150 to 3500 m a. s. l were investigated. The purpose of this study was to gain practical information on Festuca ovina. To achieve this goal، geographical distribution of the species was prepared and 45 sites were selected using two-stage sampling. Afterward، the effects of soil، topography، climate، species composition and phenology of the species were considered in all sites and morphological characteristics i. e. root، basal area، leaf، stem، seed، and chemical analysis were investigated in 6 sites. Results showed that the canopy cover of the species varied from 0. 2 to 20. 2%، and it grew in the range of 1350 to 3500 m elevation above sea level. The highest and the lowest distribution were recorded for slopes of 10 to 15% and more than 40%، respectively. The greatest distribution was found for the south-eastern slopes. The distribution of the species under the effects of ecological factors is not equal and it is highly distributed in Saein region. This species is distributed on loamy and loamy to clay soils with a moderate to high and sometimes shallow depth، with an acidic to alkaline pH، an EC of 0. 35 to 2. 6 ds/m، OC of 0. 1 to 7. 5%، phosphorous of 2 to 35 ppm، and potassium of 170 to 1025 ppm. It is suitable for restoration and improvement of rangelands with 300 to 565 mm rainfall، and the mentioned soil and topographic conditions. In low altitudes، according to phenology، seed and chemical analysis، the best time of grazing readiness started from early May to mid-June and for every 1000 m increase in altitude، 7 to 15 days delay in grazing should be considered depending on the year.

Climate change، causing global warming at a rate of 1. 4° C، is considered as a tangible reality in this century and accelerates the decline of land resources (soil، water and biological resources) especially in arid and semiarid regions of the world including our country. This is due to the annual increase of 1. 7% of the greenhouse gases in the atmosphere. The only known solution is carbon sequestration by terrestrial ecosystems with efficient management tools such as mechanical and biological operations. In order to estimate the amount of carbon sequestration، three basins (Rimeleh، Kouhdasht and Romeshgan) were selected. In the Rimeleh، Kouhdasht and Romeshgan basins 3، 4، and 3 soil profiles were dug respectively. Soil samples were collected from depths of 0 to 25 and 25 to 50 cm. The core sampling method was used to determine the bulk density. Then، carbon sequestration per unit area was determined by Walkley-Black method. The amounts for the three basins of Rimeleh، Kouhdasht and Romeshgan were estimated to be 45. 7، 54. 8 and 78. 4 tons per hectare respectively، while the mean of the control samples was 26 tons per hectare. Results of statistical analysis in Excel، SPSS and Minitab software showed a significant difference in the rate of carbon sequestration for different sites. Generally، Romeshgan site with a carbon sequestration of 78. 4 tons per hectare was a successful project in terms of carbon sequestration due to management practices and mechanical and biological operations in watershed.

Sheep fescue is one of the most important and effective grasses in the summer rangelands of Golestan Province. It is a key species in Saraliabad Gorgan rangelands، having an average production and relative consumption of 38. 9 and 41. 6% respectively. One of the important factors in determining grazing capacity is allowable use of species. Due to lack of sufficient information in this regard، this research was performed in order to determine the allowable use of sheep fescue during 2006 to 2011 at Saraliabad Gorgan rangelands. Experimental treatments in each block were included four harvesting intensities (25، 50، 75 percent and control or no harvesting). In each treatment، 10 species were assessed as replication. Results were analyzed by SAS software in split plot statistical design. The results of production showed that the effect of year، different harvesting intensities and their interactions was significant of (P<0. 01). The effect of year showed that except first and second year، there was a significant difference between the mentioned years with the third and fourth year of the study. Also، the effect of harvesting treatments showed that only a harvesting of 75% had a negative impact on production. The interaction effect between year and treatments showed significant differences for control treatment despite no harvesting. Therefore، another factor was effective in reduction of the production and it was the rain. Results of the effects of harvesting intensity on freshness and mortality of sheep fescue showed that most of the species had acceptable freshness and vitality; also no mortality was recorded for the years and treatments. According to the results and with regard to other functions of Saraliabad Gorgan rangelands، an allowable use of 60% is recommended for sheep fescue (Festuca ovina).

This research was aimed to investigate the effects of three levels of grazing intensities (no grazing، moderate and heavy grazing) on bulk density، porosity percentage and soil seed bank. The study was conducted in Khabr rangelands (Kerman province، Iran) during 2005 and 2006. After determing the sites based on the same ecological conditions، soil samples were taken from two depths of 0-15 and 15-30 cm during six periods (May to October)، as split plots based on a randomized complete block design with three replications. To study the soil seed bank، intact soil samples were taken from the depth of 0-15 cm to (36 samples per year) at the end of grazing period during two years. Artifical trampling was carried out on seedbank samples through changing bulk density of each site to another site. The results of the experiment showed that soil physical characteristics (bulk density and porosity) were significantly affected by grazing intensity. At the end of the grazing season، bulk density increased and porosity decreased in moderate (11. 7 and 12. 64 percent) and heavily grazed (17. 6 and 18. 22 percent) sites compared to control، respectively. According to the significant and irreversible increase of soil bulk density in heavy grazing site at the end of the grazing period (September and October) and the reduction of soil porosity for this site in October (in comparison with other sites)، observing the proper time for livestock exit by ranchers is emphasized to reduce the harmful and damaging effects of heavy grazing. The germination percentage and other growth characteristics of seeds and seedlings from soil seed bank indicated that artificial changes in soil bulk density had a positive effect on their growth and development.