Journal of Rangeland Science
Volume:5 Issue: 2, Spring 2015

Monthly discharge is one of the most important factors considered in designs and hydrological works. Some watersheds are not equipped with needed hydrometric equipment. In such a case average monthly discharge could be estimated from regional monthly water balance models of representative watersheds. In this study, Thornthwaite & Mather (TM) model were used in the Pishkouh watershed in arid climate of Yazd, Iran. The water balance was used for computing seasonal and geographical patterns of water availability to facilitate better management of available water resources. The water balance study using the TM model with the help of remote sensing and Geografhic Information Systems (GIS) is very helpful in finding out the periods of moisture deficit and moisture surplus for an entire basin. This study indicates that there is an annual deficit of 442.7 mm in the study basin and an annual surplus of 26.4 mm. The Pishkouh watershed has a period of moisture surplus from June to August and the remaining months are a period of deficit. Generally these mean estimated runoff values fall between the 90% confidence intervals for the measured runoff and quality of the model was satisfactory (Qual=2.86). These results indicate that the TM model can be satisfactorily applied to estimate mean monthly stream flow and potential runoff map in the arid regions of central Iran, too.

Range forage of Vicia variabilis, Astragalus spp., Medicago sativa, Prangos uloptera and Sanguisorba minor was sampled during three phenological stages from the controlled rangeland stations in Chaharmahal and Bakhtiari province, Iran. Samples were analyzed for the determination of Crude Protein (CP%), Ether Extract (EE), Crude Fiber (CF), total Ash, Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), in vitro Dry Matter Digestibility (DMD) and Organic Mater Digestibility (OMD). Higher and lower values of CP were obtained in vegetative stage of Medicago sativa and seed ripening stage of Prangos uloptera, respectively. The highest and lowest values of EE% were found in Prangos uloptera and Astragalus spp. respectively. The highest and lowest values of CF% were obtained in the vegetative stage of Prangos uloptera and ripening stage of Medicago sativa, respectively. For NDF and ADF, the lower values were found in the vegetative stage of Prangos uloptera and Sanguisorba minor, respectively and higher values were observed in the seed ripening stage of Asragalus spp. and Prangos uloptera. The highest values of DMD and OMD% were obtained in the vegetative stage of Vicia variabilis, but the lowest values were found in Medicago sativa and Sanguisorba minor respectively. Both DMD and OMD% values were reduced from vegetation to seed ripening stage in all the species. It was concluded that it is necessary to pay attention to the seasonal changes in order to conduct the quality study and determine the nutritive value and digestibility of range plants. Use of energy and protein supplement in late period of range plant growth has been recommended for the supply of essential requirements of rangeland animals.

Evaluation of range conditions and plant diversity circumstances can help to rangeland managers who establish their managerial approaches on the basis of ecological capabilities of rangeland ecosystems. Hence, surveying of rangelands was done in four sites of northern Alborz Mt. including western Alborz (Masooleh site), west to middle Alborz (Javaherdeh site), central area (Polour site), and eastern region (Ramian site). A 64 grid (1 m2) was laid down in stand area of each site and range condition was assessed by Daubenmire Method. Alpha, Beta, and Gama diversities, and plant richness and evenness were calculated in each grid using PAST v.2.03 software. Relationships between range condition and biotic and abiotic factors were done using stepwise regression method. Results showed that Ramian site had the most Beta and Gama diversities and the Javaherdeh and Masooleh sites had the most Alpha diversity as well. The Polour site had the least diversities indices because of overgrazing and poor rangeland condition. It however had high level of the plant evenness. Range conditions, soil conservation, and litter rate were the highest grades in the Ramian site than the others. Regarding the results, therefore, the rangers can be capable to balance the rangeland ecological conditions using desirable grazing capacity and pressure.

Mix cropping of alfalfa (Medicago sativa) and annual ryegrass (Lolium rigidum) may improve forage production in the rangeland and field conditions, especially in spring after the establishment year. In this study, the effects of different sowing rates of alfalfa and annual ryegrass seeds in the replacement and additive series of mix cropping were evaluated on forage yield in first year after the establishment in Shahrekord, Iran. Treatments included 100-0, 80-20, 60-40, 40-60, 20-80, 0-100, 100-25 and 100-50 percent of alfalfa (A) and annual ryegrass (R) seeds, respectively. Results showed that the highest total annual forage Dry Matter (DM) yield was obtained from A80R20 with the average value of 13900 kg ha-1 that had no significant difference with pure alfalfa. DM yield was reduced when seed rate proportion of ryegrass increased from 60 to 100% in the replacement series and the least DM yield was obtained from pure ryegrass. There were no significant differences between the additive series (A100R25 and A100R50) and many replacement series treatments (A80R20, A60R40 andA40R60). Number of alfalfa stems as one of the yield components was reduced by increasing the ryegrass seed rate proportion in A80R20 to A20R80 and A100R50. The lowest number of alfalfa stems in cuts 3 and 4 was obtained for A20R80. In general, total DM yield and number of alfalfa stems in A80R20 and A60R40 of the replacement and in A100R25 of the additive series were similar as compared with pure alfalfa, particularly in cuts 3 and 4. Since alfalfa and ryegrass are perennial and annual crops respectively, it is reasonable that less ratio of ryegrass may be used in mix cropping for the stability of forage production in subsequent years.

In recent years, rangelands have been regarded as potential carbon sinks. One of the most widely suggested options to sequester more C in rangelands is the restoration of the degraded rangelands through grazing the exclusion. In present study, the effects of exclusion on the carbon sequestration of Gomishan rangelands were investigated. Three transects were established in a key area inside and outside the exclosure. In each transect, ten plots were established systematically and in each plot, the number of plant individuals for each plant species was recorded and used to estimate the density of each species per unit area. In order to estimate the plant biomass, a few individuals of each species were sampled by the clipping and weighing method. The carbon content of aerial and root biomass were obtained by the combustion of 10 g of oven-dried samples. Five soil samples at the depths of 0–10 and 10–20 cm were taken along each transect and then, transported to the laboratory. The soil organic carbon percent was determined by the Walkley–Black method. Plant data analysis was performed by one way analysis of variance (ANOVA) and Tukey test. The rate of soil carbon sequestration inside and outside the exclosure was compared using the independent T test at significance level of 1%. Finally, the economic benefit of sequestrated carbon was estimated. The results revealed that the response of plant and soil carbon storage to the exclosure in Gomishan rangelands was positive and there was a significant difference between exclosure and grazing areas for the stored carbon of plant biomass and soil. After a 20 year exclosure, the value of carbon sequestration per hectare in Gomishan rangelands was estimated as 14743 $/h. It can be argued that the education and extension of carbon sequestration in Iran will offer new incentives to restore the degraded rangelands.

Climate changes and global warming are considered as very important challenges of sustainable development. Carbon sequestration is the easiest and cheapest way to reduce the greenhouse gases, especially carbon which constitutes the largest portion of them. In the present study, the potential of carbon sequestration in four plant species of Atriplex canescens, Haloxylon persicum, Artemisia sieberi and Agropyron desertorum was studied in the rangeland of Zarandieh, Saveh, Iran. Key areas and study sites were selected and size and number of plots were determined using the minimal area method. Then, aerial and underground organs were cut and litter of species was collected from the soil surface. Also, the soil samples were taken from two depths of 0-30 and 30-70 cm in the same plots. Samples were moved to laboratory and the rates of plant organic carbon and soil organic carbon were determined using combustion and Walky-Black methods, respectively. Data were analyzed and means comparison was made using Duncan method in SPSS software. Results showed that the rates of carbon sequestration in different species, vegetation organs and soil layers were different and increased in wooding species. Also, the rate of soil carbon sequestration in the upper depth was more than the lower one; thus, carbon storage in soil near short trees (Atriplex canescens, Haloxylon persicum) was higher than that near shrubs (Artemisia sieberi) and herbaceous form (Agropyron desertorum).

Plant litter is an important factor for soil conservation and sustainability that could modify soil chemical properties and increase the plant biomass production. The aim of this research was to compare plant litter chemical composition and its effects on soil properties in three species including Hordeum bulbosum, Poa bulbosa, Bromus tectorum. First, soil samples were taken in the depth of 0-30 cm and litter samples were collected from soil surface based on a random-systemic method using three 200m transects. Then, samples of dried plants of current and previous years were taken from 1 m2 plots. The soil samples under the plants and bare soil (as control) were also taken at the depth of 0-30 cm. Finally, the chemical composition of litter and physical and chemical properties of soils were analyzed. Results showed significant differences between species in terms of potassium (K), carbon (C), nitrogen (N) and carbon to nitrogen (C/N) ratio (P<0.01). There were also significant differences between litter and soil for chemical elements (P<0.01). The litter of species generally had higher values of all the chemical elements than soil elements except for the phosphorus (P). Hordeum bulbosum had higher values of P and C/N ratio in litter (3.23 ppm, 43.01, respectively) and higher values of P and K in the soil (10.8ppm, 400 ppm, respectively). Bromus tectorum had higher values of C and K in litter (44.88%, 1120 ppm, respectively) and higher values of C and N in the soil (1.53%, 0.50%, respectively) and Poa bulbosa had higher values of N in litter (1.53%) and lower values of C/N ratio in the soil (8.7). It was concluded that Poa bulbosa due to lower values of C/N ratio had higher litter quality than two other species for soil fertility.

Knowledge of the Saxaul dimensions used in sand dunes stabilization is considered essential for designing live windbreak in desert regions. This research aimed to collect and analysis data and was performed on the pruned and control shrubs of Haloxylon aphyllum L. in Yazd province, Iran in the last two decades. Our review clearly showed the superiority of shrubs pruned at the height of 35 cm in comparison with the other treatments as well as the superiority of soil surface height pruning with shoot thinning in the first year as compared with the other years. In the present study, data of canopy diameter and height of Haloxylon aphyllum L. from three treatments including "35 cm height pruned method", "shoot thinning method" and "control" were collected and analyzed using a completely randomized block design with three replications over 7 years (1995 to 2000 and 2005). Results of this study showed that the maximum canopy diameter of shrubs was obtained in the 35 cm height pruned method and soil surface pruning plus shoot thinning method with the average values of 261 and 240 cm, respectively with no significant differences. In addition, no significant difference was found for their heights (164 and 174 cm) and the dimension of pruned shrubs never reached to the height that was obtained before pruning. It was concluded that in designing the live windbreak with Haloxylon aphyllum L., considering the normal dimension of 35 cm height pruned shrubs at the executive levels as a practical pruning method is of high importance.