فصلنامه تحقیقات مرتع و بیابان ایران
سال نوزدهم شماره 4 (پیاپی 49، زمستان 1391)

Desertification is a global problem and most of arid and semi-arid countries of the world including Iran face the phenomenon. Desertification causes many limitations in terms of agriculture, food supply, livestock farming, industry development and so forth. The phenomenon is a process that has gradually developed and intensified and the costs of modifications increase exponentially. Therefore, identification and assessment of factors effective in desertification, and determining the regions affected by this disaster are necessary for each region. FAO and UNEP method is considered as one of the best methods to evaluate desertification in which several processes are investigated. Vegetation degradation, water erosion, wind erosion, decline in the quality and quantity of water resources and soil salinization as well as livestock and population pressure on the environment are considered as the main processes in this study. This study was carried out in a twenty-year period with considering the oldest data, aerial photographs and satellite images. To evaluate each process, several indicators were considered and selected indicators were evaluated by field and library work. Four classes of low, moderate, severe and very severe were also selected for separation of desertification intensity. Each process was studied from three aspects i.e. current situation, velocity and the potential of desertification. Desertification maps were generated in GIS and then integrated to produce final map of desertification. According to the results, 125853 ha (%23), 251504 ha (%45), and 158819 ha (%29) were classified in classes of low, moderate, severe and very severe, respectively. Severe desertification mainly was observed in mountainous areas with slopes over 60 percent, and in saline and sodic marginal lands of Kavire-e-Meighan basin. Vegetation degradation and water erosion were identified as the main factors of desertification in this basin and livestock grazing was the main cause of worsening desertification. Obtained results provide a basis for better recognition and proper combating desertification in this area.

Information on animal requirements is essential to calculate rangeland grazing capacity. Therefore, animal weight and animal unit equivalent (AUE) of each breed should be determined independently. In this research, live weight of Kabodeh sheep was determined based on average live weight of 3 and 4 years old ewes. For this purpose, two herds of Kabodeh breed were selected. In each herd, 15 three–year-old ewes, 15 four-year-old ewes, 5 three-year-old rams, 5 four year-old-rams, 10 three-month-old lambs and 10 six-month--old lambs were selected. They were weighed two times including at the time of grazing season in lowland and highland rangelands. For determination of dry matter requirement, forage quality was taken into consideration. According to the results, animal weight for herds (three and four years old ewe) was 52.66±0.86 kg. Therefore, animal unit equivalent (AUE) for rams, ewes, 3 and 6-month-old lambs were 1.07, 1.66, 0.38 and 0.51, respectively. According to MAFF equation (1984), daily metabolizable energy requirement for maintenance condition was calculated 9.89 and 10.60 Mj (including that multiplied by 1.4 and 1.5) by considering condition of rangelands and distances from watering points and plant density in lowland and highland rangelands. Dry matter requirement was calculated 1.98 and 1.80 kg based on forage quality in lowland and highland rangelands.

Determination of forage quality of rangeland species is one of the fundamental factors for evaluation of grazing capacity and management of rangelands. In this study, forage quality of Agropyron libanoticum was compared in three phenological stages in Nejh valley, Urmia. After sampling, quality indices such as ADF, CP, ME and DMD were measured in laboratory. Results showed that there were significant differences among the growth stages (at 1 % level of probability). Forage quality of vegetative growth stage was higher than that of flowering and seed ripening stages. Crude protein content decreased from early growth to the end of growth and there was significant difference among vegetative growth stage and flowering as well as seed ripening stage.

Potassium, sodium and free proline play important roles in adaptation of plant species to arid conditions. Distribution of Na+, K+ and free proline in desert plants is not clear. In this study, the accumulation of Na+, K+ and free proline was investigated in three species namely, Stipagrostis pennata, Calligonum polygonoides and Hammada salicornia. These species are naturally distributed in Irano-Turanian region. Six plants were selected from each species in similar conditions, during dry summer of 2010. Soil humidity measurement showed that all plants were in drought conditions. Half of the plants were irrigated. The quantities of Na+, K+ and proline were determined in the roots and stems of all samples. Results showed that the concentrations of free proline in the stem and root of S. pennata were significantly higher than that of other two species and irrigated S. pennata. Furthermore, the concentration of K+ in the stem of H. salicornia was significantly higher than that of other two species and irrigated H. salicornia. Also, the concentration of K+ in the root of H. salicornia was higher than that of other species, but this concentration was not significantly different from the irrigated species. Sodium, like potassium content was higher in H. salicornia, but significant difference was not observed in its quantity between irrigated and unirrigated species. C. polygonoides after H. salicornia accumulated large quantities of Na+ in its stem. Sodium content was higher in the root of H. salicornia and C. polygonoides in comparison with S. pennata. Results also showed that K/Na ratio was less in roots of unirrigated species in all three species, particularly in S. pennata while it was high in stems of S. pennata H. salicornia compared to irrigated species. Consequently, it was concluded that the three species use different strategies to cope with drought.

Segzi plain is one of the most critical areas of the province in terms of the extent and severity of desertification process. This area has a special strategic position due to the industrial centers, Shahid Babaee airport, Shahid Beheshti International Airport, railroads, transit road of Bandar Abbas- Esfahan, agricultural centers and vicinity to historical city of Esfahan. Consequently, investigation on the main cause of desertification phenomenon is the main objective of this study. Therefore, IMDPA model was used to study desertification intensity in Segzi plain. In this research, two criteria including geology – geomorphology and soil, consisting of seven indicators (sensitivity of the formation, land use, and slope based upon geology – geomorphology criterion, and soil texture, soil depth, percentage of stone and gravel, and EC based upon soil criterion) were studied. Desertification intensity map was generated by using geometric mean of criteria. With regard to the geometric mean of criteria, soil criterion, with a numerical value of 3.4, and geology – geomorphology criterion, with a numerical value of 3, were classified in severe desertification class. Finally, the severity of desertification (DS) was calculated to be 3.26 indicating that the region was in severe desertification class. Results showed that EC, with an average value of 3.75, was classified as very intense indicator and had the most impact on desertification of the region.

Genu protected area is located in the north–west of Bandar Abbas and its summit is 2347 meters above sea level. In this study, soil seed bank was investigated in vegetation communities. Soil seed bank plays a role in the revival of vegetation after degradation. In protected areas, understanding of the type of soil seed bank in terms of the production capacity of persistent and non-persistent seed bank is valuable to preserve the species especially endemic and rare species. In this study, sampling of the soil seed bank was conducted before precipitation. Sampling points were selected from 50 points in both depths of 0-5 and 5-10 cm of the soil surface to determine soil seed reserves. A total of 135 samples were selected for the study of plant sociology. Trays containing the samples were placed in a greenhouse and were irrigated regularly. The potential of soil seed reserves was investigated in terms of seed persistence in soil, and according to the results, significant differences were found in terms of seed density per meter square at different depths of soil and the life form of species in different communities. Among life forms, therophytes were more abundant in the soil seed bank while tree and shrub species were scarce. Species with persistent soil seed bank was mainly annuals. From 810 samples of soil seed bank, cultivated in the greenhouse, 3934 seeds were germinated of which 2933 and 1001 seeds were related to the depths of 0-5 and 5-10 cm of soil surface, respectively. In total, the number of seeds was related to 163 species of which 44 species had persistent seed bank. Species in the sampling units of soil seed bank with at least two seeds in the depth of 5-10 cm of the soil surface were considered as species with persistent seed bank. Other species in the region which had non-persistent seed bank were more vulnerable to degradation. In other words, if the vegetation is destroyed, they will not be able to revive.

Each of the range species has certain production in different months and years of grazing seasons. Without understanding the production characteristics of species during grazing season, planning and livestock management is not feasible. Therefore, understanding the annual and monthly production of different rangeland types is essential for efficient and effective management of livestock grazing. Consequently, relationships between forage production and climatic variables should be studied. For this purpose, annual forage production was measured in research exclosure of Khoshkerood-Saveh during 2007-2010 by clip and weigh method‬. Monthly rainfall in this period was calculated using Saveh synoptic station data and then the amount of cumulative rainfall in winter and spring of each year was calculated. Afterward, the relationship between production and winter and spring rainfall as well as rainfall of different months of winter and spring was studied separately. Statistical analysis was performed using Minitab software. Results showed that winter rainfall had no significant impact on the production of perennial species. However, cumulative rainfall in winter and spring showed different effects on forage production of the species. In other words, a significant relationship was observed between the production of Artemisia sieberi and Salsola laricina and rainfall while no significant relationship was recorded between the production of Stipa hohenackeriana and Poa sinaica and rainfall. Also, there was a significant relationship between cumulative rainfall in March and April and annual production of the species

Many studies have been carried out to assess and prepare desertification map in the worldIn order to assess the current situation of desertification intensity, a study was carried out in an area of 88350 hectares in Zahak region of sistan. In this study, at first, based on combining information extracted from topographic and geologic maps, aerial photos and field survey, the study area was divided into 11 geomorphologic faces and each face was considered as the main unit for evaluating the current situation of desertification. With regard to the analysis and combining FAO-UNEP and MICD models, as the most famous models of desertification intensity assessment in Iran and world, it was attempted to identify effective indices based on wind erosion to select the best ones. These indices were evaluated in a regional model of desertification assessment with regard to the numerical value of each index in each work unit and then in whole study area. Finally, the current situation of desertification intensity of the study area with emphasis on wind erosion criterion was estimated in four classes of insignificant and low, medium, intense and very intense. Results indicated that the study area with respect to desertification intensity was placed in the classes of medium (about 734.33 hectare (0.9 %)), intense (about 61473.38 hectare (73.6 %)), and very intense (about 21310.22 hectare (25.51 %)). Also, the weighted average of quantitative value (DS) was estimated to be 25.52 in the whole area indicating an intense desertification in the region.

Drought resistance of 24 accessions of Agropyron trichophorum was examined based on forage yield in a complete block design with three replications under normal and dry land farming system. Drought resistance indices of genotypes were measured for forage dry matter yield of two environment conditions including sensitivity to stress index (SSI), tolerance (TOL), mean productivity (MP), drought tolerant index (DTI), mean harmonic (MH) and geometrical mean of productivity (GMP). According to the results of variance analysis of drought resistance indices, significant variation was observed among accessions. Results of mean comparisons showed that genotypes 10 (Semirom), 23 (Mazandaran), 24 (Gorgan), 5 (Chaharmahal), 17 (Yasuj) and 9 (Eghlid) had higher values for forage dry matter yield in both environment conditions. With regard to the drought resistance indices, genotypes 10 (Semirom), 23 (Mazandaran) and 24 (Gorgan), showed the most resistance to drought stress. Obtained results were confirmed by results of cluster analysis and principle component analysis.

Vegetation cover is one of the most important factors for sustainability of ecosystems, thus recognizing and understanding factors that affect establishment and distribution of vegetation communities are necessary. This study was aimed to determine the relationship between vegetation properties (vegetation cover and density) and environmental parameters of rangelands. The study area was about 4600 ha, located at Polour, Mazandaran province. Land units were considered as the basis of research, and after preparing maps of slope, aspect, elevation, lithology and geomorphology and combining the maps, a single working map was generated. Systematic randomized sampling was used and performed along 3 transects of 100 m length. Ten quadrates of 1m2 were established along each transect at 10-meter intervals. Three soil samples were taken in each area and topography properties were recorded. Multivariate analysis and Canonical Correspondence Analysis (CCA) were used to determine relationship between soil and vegetation data using CANOCO software. Results showed that the percentage of canopy cover and density of the species was different and was influenced by soil properties and physiographic factors. Among physiographic factors, aspect and slope had a significant relationship whit vegetation cover and density. Among soil factors, texture, N, P, pH and litter were the most important factors that influenced vegetation cover, and OM, P, pH and Ec had the most influence on density.

Drought has a major influence on morphological and physiological characteristics of plant species. Drought stress has a direct relationship with germination characteristics including germination percentage, seedling length (mm/plant), root to shoot ratio, seedling weight (g), ratio of dry weight to fresh weight of seedlings (g.dfw-1) and seed vigor index (V). In this research, effects of drought stress on these characteristics were examined on four genotypes of Bromus inermis (Alborz 303, Mazandaran 3151, Firozkuh 3966 and Esfahan 200060) under laboratory and greenhouse conditions. In greenhouse experiment, three physiological traits including chlorophyll, carbohydrates and proline contents were measured. Drought treatments included four levels of osmotic potential (0, -0.3, -0.6 and -0.9 MPa) in germinator and four levels of osmotic potential (FC, 25% FC, 50% FC and 75% FC) in greenhouse, made by Poly-Ethylene-Glycol (PEG 6000) solution in laboratory and weighting method in greenhouses, respectively. Results showed that Esfahan (200060) genotype was better than two other genotypes in terms of germination percentage under the two conditions. Increasing drought stress increased proline and carbohydrate and decreased the chlorophyll content.

In this study, the effects of Mianeh Zeolite and Taravat® A200 polymer on moisture content and available water content of a coarse-textured soil were investigated. Mianeh zeolite was applied at four levels (0%, 2%, 5%, and 8% on weight basis) and Taravat® A200 polymer was applied at 5 levels to the soil in a completely randomized experiment with 3 replications. Soil moisture content was determined at suctions of 0, 5, 7.5, 10, 33, 100, 500, and 1500 kPa using hanging water columns and pressure plate apparatus. The water retention curve model of Campbell (1974) was fitted to soil data. Results showed that both soil conditioners enhanced soil moisture content at measured soil suctions. The addition of more conditioner caused a larger response of soil. For example, application of 8% zeolite elevated the volumetric filed capacity from 11% to 13% and therefore increased available water content by 2% compared to the control. Also, addition of 0.2% A200 polymer increased the available water content by 6%. In addition, soil conditioners modified the shape of the moisture characteristic curve of the soil and influenced the parameters of water retention model in a manner exhibiting reduced water release rates plus the added benefit of an additive and/or a synergistic effect. For instance, simultaneous application of 5% Mianeh zeolite and 0.2% Taravat A200 polymer increased e from 0.21 to 2.00 and decreased  from 7.37 to 5.40 and thereby increased the available water content by 7%. Simultaneous application of these amendments is possible and may reduce the needed water and/or increase irrigation intervals. Simultaneous application is also cheaper and probably will prevent plant root damage.

In order to study the grouping of Agropyron tauri populations, 13 populations were investigated in a randomized complete blocks design with three replications. The study was performed in research field of Islamic Azad University of Tabriz in 2010. In this study, a number of traits including plant height, tiller number, leaf number, flag leaf length, first leaf length, second leaf length, first internode length, second internode length, crown cover, fresh yield, dry yield, fresh weight of single plant and dry weight per plant were evaluated. Analysis of variance showed significant differences among populations for all measured traits. Thirteen populations were classified into three clusters by cluster analysis of standardized data, based on Euclidean distance and Ward method. This result was in consistent with the height of geographic regions from which populations were collected. In principal components analysis, four components were introduced, and the traits of fresh and dry yield showed high and positive coefficients in first component. Results of cluster analysis were confirmed by results of principal components analysis.

Grazing and harvesting are two major ways of utilizing natural and artificial grasslands. Current research was aimed at studying the effects of shoot cutting frequency on total phytomass, above-ground phytomass, underground phytomass, the condition of tillering, and the tolerance of four halophytes (P. distans, A. littoralis, A. lagopoides and J. articulates) against cutting. This experiment was carried out in a completely randomized design with 7 replications. Four mentioned species and four different cuttings were considered as treatments. Seedlings of four species in growth stage were collected from grasslands of Inchebroon, located in north of Agh-ghala, and were cultivated in the pots. During the growth period, aerial parts of the species were cut at 6 cm above the soil surface of pots in four cutting treatments including once every week, once every two weeks, once every four weeks, and control treatment. Results indicated that total phytomass, above- ground phytomass and underground phytomass of A. littoralis, A. lagopoides and J. maritimus reduced as a response to the stress of cutting compared with control treatment. Consequently, these three species cannot retrieve total phytomass in comparison with control treatment. Total phytomass of P. distans remained stable in all treatments; therefore this species is able to retrieve phytomass loss completely. Repeating cutting decreased the number of shoots in four species. According to the results, in one-year experimental conditions, P. distans was identified as a high-tolerant species against cutting while A. littoralis, A. lagopoides and J. maritimus showed a medium tolerance.

Blue panic (Panicum antidotale) is a perennial species with warm growing season and very limited natural distribution in southern Iran. It is considered as a main species of tall grasses in sandy rangelands. This species is succulent and nutritious at early growth stage but soon becomes woody and fibrous. Forage production is good in years of early growth and establishment but its vigor reduces over time. Due to its appropriate forage value, blue panicgrass is widely used in areas with light soils where biological soil conservation practices are needed. This research was aimed to study the response of blue panicgrass to harvest frequency and intensity and determine the appropriate intensity to increase the stability and survival of the species at Khuzestan sand stabilization station. The experiment was conducted in a split-plot design with four replications including main treatment (harvest frequency) and secondary treatment (harvest intensity) at three levels. Results showed that the third level of main treatment (harvested every 18 days) had a better impact compared to other treatments. After three years of experiment, average number of vegetative buds was 36 in superior treatment. Better stability and survival, and more vegetative buds in the successful treatment give the species more time and opportunity for repair and re-accumulation of food supply and production.

To investigate the effects of humic acid on vegetative characteristics of a rangeland species, Festuca arundinacea, a greenhouse experiment was conducted at Damavand city, Iran, based on a randomized complete block design. Levels of 0, 75, 150, and 225 kg per hectare of humic acid were used in a form of granules as different treatment levels. Several vegetative characteristics were studied and recorded on the single plants. Analysis of variance showed that treatment effects on leaf area, leaf number, leaf, stems and whole canopy fresh weight, leaves, stems and roots dry weight, root length, canopy to root ratio, total chlorophyll and chlorophyll a were significant at 5% level. Also, the treatment effects on canopy dry weight and root fresh weight were significant at 1% level. Treatment effect was not statistically significant on tiller number, collar diameter and chlorophyll b. Maximum dry and fresh root weight were obtained by 75 kg per hectare humic acid. Most of the attributes were highly affected by applying 225 kg per hectare humic acid.

The objective of study on phenology of range plant species is to assess the changes of different phenology stages (germination, flowering, seed maturity stages, autumn growth and winter dormancy) in order to adjust range utilization programs, prevention of early or late grazing, recognition of nutritional value of the plant species, determining livestock entry and exit time and seed collection. Artemisia sieberi is a shrubby species with an appropriate forage value distributed as a dominant species in arid and semi arid steppe regions of Iran. It is resistant to drought and relative salinity which widely grows in loamy, sandy and loamy clay soils. In this study, phenological stages of Artemisia sieberi were investigated in six different sites of steppe regions of Iran. Accordingly, data of the phenological stages were recorded for vegetative and reproductive stages respectively in 15-day and 7-day intervals. With regard to the direct relationship between phenological stages and climatic factors especially temperature and precipitation, these data were taken from the nearest synoptic station for each site. According to the results, vegetative growth stage of Artemisia sieberi starts from early March early April and continues to July if moisture is available. The flowering stage starts from early July and continues to late October. Seed ripening stage gradually starts from early September to late January. The start of the winter dormancy is late January which continues to early February. Our results show a long-term phenology for Artemisia sieberi indicating its resistance to environmental conditions. Consequently, comprehensive recognition of phenological stages of Artemisia sieberi as a key species enables us to manage the grazing, adjust the entry and exit time for livestock, grazing intensity and appropriate grazing systems to be applied by range managers and utilizers.