فصلنامه تحقیقات مرتع و بیابان ایران
سال بیست و دوم شماره 3 (پیاپی 60، پاییز 1394)

In this study, the autecology of Hyparrhenia hirta was studied in rangeland ecosystems of Khuzestan province. All vegetation maps were prepared using topographic maps at a scale of 1:50000 and than all habitat characteristics including topography, climate, and soil, as well as associated species, presence, roots, phenology, regeneration, palatability, and frequency were studied. The results showed that Hyparrhenia hirta grows at altitudes of 60 to 900 meters above sea level in the steppe and semi-steppe regions. The highest density of Hyparrhenia hirta is at altitudes of 300 to 600 meters above sea level. The soil texture is sandy with gravel. The average rainfall was 320 mm annually and air temperature varied between 24.5- 26.5 ° C. Vegetative growth was observed from late September to the end of December. Seed ripening and seed dispersal occurs in the second half of May and in June, respectively. The roots of Hyparrhenia hirta are widespread in horizontal and vertical directions and vertical growth is limited under heavy grazing. This plant is not palatable; however, in the absence of palatable plants, it is used by livestock.

This research was aimed to investigate the effects of exclosure on vegetation cover and soil properties in the rangelands of Gardaneh Zagheh, Lorestan.For this purpose, constant transects of 60*50 cm were placed with a distance of 1.5 m, and 10 quadrates were established on each transect. Vegetation changes were investigated inside and outside of exclosure. In addition, soil profiles with a depth of 40 cm were dug and soil samples were taken inside and outside of exclosure. According to the results, during the first and last sampling, the forage yield inside of exclosure was calculated to be 36.1 gm-2 and 67.2 gm-2, and outside of exclosure, it was calculated to be 46.1 gm-2 and 91.8 gm-2, respectively. The bare soil outside of exclosure was also higher as compared with inside of exclosure and soil conservation was calculated to be 74% and 95.6% in the years of 1998 and 2004, respectively. Our results clearly showed that in the last year of exclosure, the rock and gravel cover decreased inside of exclosure but it was increased up to two times outside of exclosure.

This research was aimed to investigate the mineral elements of four range species including Dactylis glomerata, Poa bulbosa, Bromus tomentellus, and Stipa barbata in the summer rangelands of Taleghan at vegetative, flowering, and seeding stages. Therefore, in each growth stage, at least five plant species were collected. The data were analyzed by the one-way analysis of variance, and in order to determine the sources of variations, the Duncan test was used. In addition, to meet the daily livestock requirements for maintenance condition, the amount of aforementioned elements was compared with their critical level using the t test. According to the results, the amount of minerals decreased with the development of plant growth. Moreover, these values differed among the species studied at each growth stage. Generally, the species studied here could supply the daily livestock requirements in terms of calcium, iron, copper, manganese, and cobalt; however, the amounts of macronutrients, especially sodium and magnesium were less than the required value. These results could be used to estimate the daily livestock requirement at different times and years.

Non- structural carbohydrate reserves in plants show their ability for regrowth after grazing. This study aimed to clarify the effectts of different harvesting intensities on changes of soluble carbohydrate reserves in Stipa hohenackeriana and Salsola laricina. From each species, 40 individuals (bases) were selected during 2007-2010. The treatments consisted of different harvesting intensities (treatments) including control, 25, 50 and 75%. Sampling of treated base took place in autumn and spring. Soluble carbohydrates were measured using the phenol - sulfuric acid procedure. Split plot design based on CRD was used. To analyze the data, ANOVA and to compare the means Duncan test was made. Based on obtained results, the effect of species and season on amount of carbohydrate was significant. Different harvesting intensities of control, 25, 50 and 75 percent had amount of 2.75, 2.73,2.64 and 2.51(mg/g-1) carbohydrates, respectively. Although the amounts numerically were different but no significant differences were observed among them. Existing of sufficient amount of soil moisture in autumn leads to re-growth in Stipa hohenackeriana, coinciding with seed ripening in Salsola laricina. Therefore, regrowth and seed ripening causes carbohydrate depletion in both understudy species. On the other hand, spring is the growth season of both species in which carbohydrate is consumed for growth initiation. Consequently, the depletion of carbohydrate reserves happens. These reasons lead to no-significant effect of different harvesting intensities on carbohydrate reserves in underground part of Stipa hohenackeriana and Salsola laricina.

Heavy metals are found naturally with different amounts in all soils and knowledge on their spatial and temporal variations plays an important role in the sustainable management of ecosystems. This study aimed to assess the distribution of various amounts of iron and zinc in Absard Region of Damavand. For this purpose, 60 soil samples were taken from range and farm lands with an area of 4,000 hectares. The total amount of zinc and iron was measured using atomic absorption as 96/66 and 20743 mg kg, respectively. In order to predict the spatial distribution of total zinc and iron, methods of Kriging and inverse distance function were used and the most appropriate model for interpolation was selected by means of cross validation and error evaluation methods. Results showed that for zoning soil properties, Kriging methods are superior compared to IDW (inverse distance weighting). Finally, with regard to the most appropriate model for interpolation, zoning maps of soil properties were produced in GIS.

This study investigates the efficiency of IRS-p6 LISS-III data to discriminate the vegetative forms in Nojmeh rangeland of Mazandaran. The data of soil surface cover were collected based on dominant plants using quadrate (25×25 m2) and randomized sampling techniques. Then, the canopy cover of each species was extracted for all plants including grasses, forbs, shrubs, bushy trees, as well as the percentage of bare soil and gravel. To correct the LISSIII images, ETM+ fusion image was used as data-base with 18 selected points, extracted with 0.54 pixels RMSE. After that, vegetation indices were calculated from each bands and their digital number (DN) were extracted from the sampling points. The results of data analysis confirmed that among the plant groups (grasses, forbs, shrubs, and bushy trees) only grasses cover and bare soil had significant relationships with LISSIII data. Among the extracted indices of vegetation, the highest correlation belonged to the bare soil with MND (r= 0.41), GI (r=0.40) and OSAVI with grasses cover (r=0.38), respectively.

In this research, the long-term monthly water balance of Yazd-Ardakan watershed, with an area 16000 km2, was developed based on Thornthwaite–Mather method in GIS. Model input data included the monthly maps of temperature, precipitation, and soil water holding capacity in roots with a cell size of 60 m, and model output included monthly maps of actual evapotranspiration, map of soil water storage, the lack of moisture and excess water, determined by Ilwis software. Results showed that more than 80% of rainfall exited the watershed as evapotranspiration, approximately 8% as surface runoff, and the rest as subsurface runoff in the study area. The amount and area of groundwater recharges varied between 20-50% in different months.Groundwater recharge occurred only in December to March, whose value varied between. 5 mm in December to 17 mm in January.

For assessing clipping (simulated grazing) effects on Stipa barbata as an important species, a half hectare exclosure field was established before 2007 growing season in Majidabad paddock. Inside the exclosure area, 40 plants were selected of which 10 replications were allocated to each specific treatment of ocular-estimated hand clipping of 25, 50 and 75 percent of annual growth. Ten replications were assigned as control (unclipped) plants. Clippings were done monthly during the three months of current grazing season. Monthly-clipped plant materials were dried in free air to calculate the accurate clipping intensity. In addition, the residues of all plants (also controls) were clipped and dried simultaneously at the end of growth season. The study was done for four years. A split plot in time was used as the statistical design and analysis. The results showed that the main effect of year and different clipping intensities and interactions effect of different clipping intensity and years were significant on forage production but no significant difference was found on final height and number of reproductive branches. Most and least amount of production were related to the years of 2007 and 2008 with 508 and 167 mm of rainfall, respectively and 75% treatment (severe clipping). As the overall conclusion, regarding the environmental and management variations of this species, it is adapted with light clipping (25%) and maximum allowable use of one third of the annual yield growth.

In recent years the utilization rate of renewable resources especially the pressure of livestock grazing has increased. Uncontrolled livestock grazing has caused reduction of quantity and quality of forage، therefore، studying the effects of exclosure on vegetation changes is very important. In this research، the effects of exclosure on vegetation changes of Sahand rangelands were studied during 2001 to 2006. The vegetation changes were investigated inside and outside the exclosure area، using fixed transects. The results showed that total canopy cover and canopy cover of perennial grasses including Agropyrum trichophorum، Bromus tomentellus، Dactylis glomerata and Festuca ovina increased significantly inside the exclosure area (P<0. 01). In terms of palatability، class I species increased significantly (P<0. 01). Cirsium haussknechtii، one of the important invasive species of the area، decreased significantly inside the exclosure area. There was no significant changes on total canopy cover of outside of the exclosure area. Canopy cover of perennial grasses and perennial forbs decreased (P<0. 05) and shrubs canopy cover increased (P<0. 01). Class I species decreased and class III species increased in outside of the exclosure area but it was not statistically significant. Canopy cover of Cirsium haussknechtii increased in outside of the exclosure area (P<0. 05). No significant changes of soil organic matter were detected inside and outside of the exclosure area during six years.

To study water, soil, and vegetation characteristics in the wet edge of Kashan desert, 11 sites were selected and the data including water quantity and quality, soil, groundwater level, and vegetation types were collected. By drilling the wells, the water level was measured in different months of the year. In order to study the quality properties of water and soil, water samples were taken in two wet and dry seasons and soil samples were taken from nearby wells.The results showed that the minimum and maximum depth levels of water for the study wells were obtained at a distance of 47 cm in the well no. 3 and 299 cm in the well no.4, respectively. Fluctuations in water level of wells during the year were not so much, calculated to be 15 cm. The highest and lowest soil EC was 174 and 6.6 dS.m-1, respectively. The minimum and maximum water EC was 4 and 128 dS.m-1. In general, water depth was increased and EC was reduced by moving away from the lake. With considering the establishment of plants in the area with a salinity less than 40dS.m-1, 3880 hectares (23% of the study area) is suitable for the cultivation of hydro-halophytes.

Frequent occurrence of patches with dominant shrub species is a common characteristic for arid and semi-arid ecosystems. In this study, the effect of shrubby patches on soil seed bank characteristics was studied in mountainous rangelands in Vaz watershed, Mazanderan province. Soil samples were taken in spring 2011 and spread out under natural conditions in greenhouse to germinate the seeds. Germinated seeds were identified and seed density was calculated per square meter. Sorensen similarity between soil seed bank and above ground vegetation, seed richness, and diversity were estimated and compared between patches and inter-patches. The results showed that seed density in patches was significantly higher than that of inter-patches. In addition, Shanon diversity index and richness were significantly higher in patches than those of inter-patches (1.81 vs. 1.37 and 11.86 vs. 7.9 per plot, respectively). Similarity between above ground vegetation and soil seed bank was significantly higher in inter-patches than that of patches (22.5% vs. 15.5%). The results of this study indicated theimportance of small-remained patches with shrub species in seed conservation of grasses.

Management of range allotments in recent decades has always been one of the main challenges of rangelands.The current study was aimed to investigate the factors affecting rangeland degradation within collective utilization system. This is a descriptive study conducted based on field measurements and questionnaires. Therefore, a questionnaire was designed and its validity was confirmed at level of 85%. The number of samples was calculated to be 37 beneficiaries using the Cochran formula.The data, collected through questionnaires, were analyzed using SPSS. According to the results of Spearman's correlation coefficient a significant relationship was found between the structure of utilization and rangeland degradation. The results of Kruskal- Wallis test showed that among the individual characteristics of the beneficiaries, level of education showed a significant difference with rangeland degradation. In other words, rangeland degradation decreased in the range allotments by increasing education of beneficiaries. The most degradation was observed in the Yakhli as compared to other range allotments.

Many natural fires occur in arid and semi arid rangelands and may result in destruction of desirable forage as well as soil erosion, which eventually will lead to great environmental and financial losses. To study the effects of fire on annual and perennial grasses, a research project was carried out in semi steppe rangelands of Kordan, located in southern Alborz Mountain. A completely randomized block design was used with two treatments (control and burned rangelands) and 20 replications (quadrates) for three years (2008-2010). Vegetation of the studied area (control and burned rangelands) was examined using transects and quadrates in the first spring season after fire with one year intervals for three years of research. In each quadrate, the percentage of canopy cover was measured. Statistical analysis was performed through a factorial experimental design and means comparisons were done by Duncan's test. The results showed that in the first and second year of the study, the presence of perennial grasses was more in control area with no significant difference while in the third year, their presence was equal in both studied area. On the other hand, our results indicated that fire had a positive effect on the presence of annual grasses (p<0.99) and the differences between years and also between the studied areas were significant.

Trifolium radicosum (Boiss. & Hohen.) is a perennial range legume growing on steep or moderately steep slopes in high altitudes areas of the central Alborz Mountain with a cold Mediterranean climate. Establishment of this species in cold, high-altitudes, and steep slopes with heavy snow falls prevents soil degradation and erosion. In this regard, the species has a great importance in ecological and range conservation point of view. Overgrazing, high nutrient values, palatability, as well as habitat susceptibility may cause the species to face the risk of extinction. In order to evaluate the possibility of long-term conservation of the Trifolium radicosum seeds, with low degree of germination (35.67%), cryopreservation approach was evaluated. Subsequent to cryopreservation, three pre-cryopreservation methods including PVS2, desiccation, and 30% glycerol were applied. The treated seeds were transferred into liquid nitrogen (- 196°C) for one week, one month and one year, respectively. The cryopreserved seeds were removed from liquid nitrogen and imposed to heat shock, surface sterilized and were transferred between sterile moist papers in petri dishes or sown in pots under greenhouse conditions. The cryopreserved seeds of different storage times and precryopreservation treatments were survived under liquid nitrogen conditions, germinated normally, and grown to seedlings. Differences between cryopreservation times for most of the attributes were not significant. However there were significant differences between pre-cryopreservation treatments for some of the attributes, such as germination (29.33, 26.33 and 21.67% for desiccation, PVS2 and 30% glycerol in one weak cryopreservation period). In clonal propagation experiments under greenhouse conditions, the root cuttings showed excellent results compared to that of the stem cuttings.

This research was conducted to investigate sheep grazing behavior in semi-steppe rangelands (Gavan ban, Qorveh, Saral, Karsanak and Sarali Abad) during 2007-2010. For this purpose, the distance traveled per day, the speed of movement, the time spent for rest, and the time taken to move were measured using GPS..At the end of grazing, all data were extracted using track mode in ILWIS software.Measurements were repeated each month during the grazing season (flowering to seeding stages).Our results clearly showed that the distance traveled by sheep in flowering stage was higher as compared with other stages and the lowest distance traveled by sheep was related to August and September. According to the results, the maximum and minimum time spent for grazing was related to September and May, respectively. In addition, the maximum distance traveled by sheep was recorded on the slopes from zero to 8% and the lowest on the slope more than 50 %.

Drought is a natural event that can bring considerable damage to human life. The prediction of drought can play an important role in the water resources management during the drought periods. Currently, ANNs have shown great ability in forecasting non-linear time series. On the other hand, wavelet transform improves the resolution using decompositions of an original time series to sub-signals. In this study, three hybrid models including perceptron neural network wavelet (MLP-W), recurrent network wavelet (TR-W) and time lag recurrent network wavelet (TLRN-W) were presented for drought prediction and then, the Standardized Precipitation Index was predicted using these models for 12 months ahead in Yazd meteorological station. In addition, in order to evaluate the effect of wavelet transforms on performance of hybrid models, the results of hybrid models were compared with the results of the single ANN models using statistical criterion including R, RMSE, and MAE. Finally, the results of hybrid models showed a higher correlation coefficient and lower error in comparison with single ANN models.The correlation coefficient, RMSE and MSE in the best hybrid model were calculated to be 0.977, 0.05, and 0.020, while these values in the best single ANN model (TLRN) were. 895 and 0.07 and 0.020, respectively. In general, it was found that wavelet transforms could improve the performance of neural networks in drought prediction.

Geological formations are one of the most distinguished aspects of desertification, affecting the water quality of the Mond River. A number of 15 salt domes in this watershed have a significant impact on the water quality of Garagaj and Firozabad rivers, forming the main branches of the Mond River. In the current study, samplings was done in order to determine the water quality of the rivers before and after the salt domes and qualitative and quantitative statistics were collected from hydrometric stations along the river. The samples were analyzed for pH, EC, SAR, cations, and anions. Wilcox diagrams were made for each station. In addition, the measured discharges were classified into different classes by using long-term daily discharge data. Changes in water ion levels were investigated at different longitudinal intervals of river using the average values of major anion and cation concentrations, and finally the role of the study formations in degradation of water quality of the Mond River were detected. According to the obtained results, three salt domes, located in the south west of Firoozabad, were the main causes of Firoozabad River water salinity, having the greatest impact on the water quality of Mond River. In addition, the Korab River, originating from saline springs of Khorab salt dome, had considerable impact on the water quality of Firozabad River. Finally, the saline water of the Firoozabad River, entering the Mond River, was identified as the main cause of salinity.

A pot trial was conducted to investigate the effect of a superabsorbent polymer on the growth of Panicum antidotale and nitrogen leaching in three soil textures (heavy, medium and light-textured soils) and three irrigation regimes (4, 8, and 12-day intervals). Results showed that the greatest amount of plant growth and dry biomass was obtained at moderate-textured soil and 14-day irrigation interval. According to the obtained results, the effects of polymer, irrigation regime and soil texture on dry matter production, plant height, and nitrogen leaching were significant. Furthermore, the interaction effects of irrigation regimes and soil texture on dry matter production and nitrogen leaching were significant. The highest dry matter production (7.2 g) was obtained at medium-textured soil with polymer at a four-day irrigation interval. In treatments without polymer at a light-textured soil and a 12-day irrigation interval, plants were lost before harvesting. Our results clearly showed that the studied treatments caused to the increased height of Panicum antidotale. Statistically, the effects of a four-day irrigation interval and a heavy-textured soil were the most significant. In addition, the effects of polymer, irrigation regimes, and soil texture treatments on nitrogen leaching were significant. The interaction effects of irrigation and soil treatments showed that the amount of nitrogen leaching decreased by increasing irrigation intervals. The application of polymer obviously decreased nitrogen leaching from 880 mg N/l in control treatment to 550 mg N/l in soils containing polymer material.