فصلنامه تحقیقات مرتع و بیابان ایران
سال بیست و یکم شماره 4 (پیاپی 57، زمستان 1393)

Negative and positive interactions among plants have important role for species coexistence and community diversity. The strength and direction of the interaction effect may change with environmental disturbances such as grazing and fire. This study was aimed to evaluate the effects of environmental disturbances such as fire and grazing on interactions between shrubs and herbs in rangelands of Goghar Bafte. Hence, beneath 20 dominant species of Artemisia aucheri and 20 open patches, a quadrate of 20 cm×20 cm was plotted and the variation in the biomass, richness and vegetation cover of herbs were measured in regions under exclosure, fire and grazing. Results showed that biomass and vegetation cover of herbs were increased by shrub presence because of positive interaction between shrubs and herbs inside exclosure. Although the facility of shrubs was reduced by grazing and fire, its rate was not equal in both places. Under grazing, interaction between shrubs and herbs remained positive but shrubs were severely damaged by fire and the interaction between species altered from positive to negative. The overall conclusion is that fire plays a more important role in changing the interaction between shrubs and herbs.

Identifying the border of saline lands is the first step to deal with the problem of salinity in these regions. This research was aimed to investigate the relationship between edaphic, climatic and vegetative factors in each habitat and its extension to other similar areas. In the current research, the vegetation types were detected by Landsat satellite images. For this purpose, a soil profile was dug in each vegetation type and where water was found, samples were analyzed. In addition, a number of soil profiles were dug in areas without vegetation. Results showed that half of the studied vegetation types grew on saline soils and the other half grew on non-saline soils. The soil of the study area was classified as saline and alkaline soils. Seidlitzia sp. and Aeluropus sp. were identified as the most and least resistant halophytes, respectively. Geological formations containing evaporite deposits (Neogen), Qom formation deposits, little precipitation, Qom salt dome, saline water flowing in the region and geomorphological position were the factors increasing the salinity of the study area.

Knowledge of the phenological stages of species constituting a plant community has a considerable importance in grazing management to achieve the goals of sustainable production. The study of plant phenology is critical for monitoring, management and conservation of ecosystems. In this research, the phenology of two shrub species including Artemisia aucheri and Thymus kotschyanus was investigated for four years during 2007 to 2010. For this purpose, 10 samples were selected from each species and the phenological data were recorded every 15 days and every 7 days in the vegetative and reproductive stages, respectively. Results showed that the start and end time of growth in different years in these two species differed under the influence of temperature and precipitation. The flowering stage of Thymus kotschyanus began in the first half of June, and the seeding stage started in the first half of July, continuing to the first half of August.The vegetative growth of Artemisia aucheri started from the second half of May, the flowering stage began in the late August and the seeding stage started from the last week of September, continuing for 2-3 weeks.

A temporary model to assess desertification and providing the map of land susceptibility to the reducing processes of land efficiency was proffered by FAO and UNEP. The results of regional implementation of the FAO and UNEP method in Gharachay watershed are presented in this article. In this method, five major processes of land degradation were evaluated with two aspects including "current status" and "inherent risk". For any of these aspects, the maps of low, moderate, severe, and very severe desertification were separated and the area of each class was calculated. Then, the maps of main processes affecting desertification were integrated together and two maps including "current status and inherent risk" were provided. Afterward, the maps of livestock pressure and human population were prepared. In order to obtain the total risk of desertification, the four mentioned maps were integrated and finally the risk of desertification classes were calculated. In view of the current desertification status in the studied region, the following results were obtained: The highest vegetation decline (76%) was observed in the east, south, and center of the region. The highest percentage of water and wind erosion (45.2%, 57.9%) was obtained in the south and east respectively; the highest soil salinization (34.7%) was observed in the east. In addition, the highest loss of groundwater resources was observed in the center and east of the region. The highest livestock pressure (58.3%) was recorded in the center of region; however, population pressure had little impact on environmental degradation. The area of each category, including low, moderate, severe, and very severe, was calculated to be 39.4, 27.9, 25.1, and 7.3 percent, respectively. Overall, according to the obtained results, the natural and human factors, particularly livestock pressure, were effective to create these conditions.

Despite the high resistance of black saxual (Haloxylon aphyllum) to environmental stress such as drought, there is the possibility of further resistance in different populations. This experiment was carried out to determine the drought tolerance in seven populations of black saxual(Yazd, Esfahan, Semnan, South Khorasan, Sistan va Blochestan, Kerman) under three moisture treatments (100%, 50% and 25% of field capacity) using small weighing lysimeters. The study was conducted in Yazd Shahid Sadoqi Research Station during 2010-2012 using a randomized complete block design with three replications. The effects of soil moisture treatments were studied on morphological traits such as shoot dry weight, root dry weight, root to shoot ratio and physiological traits such as leaf and root osmotic potential, relative water content, water use efficiency, total chlorophyll, chlorophyll a, chlorophyll b, Na+ and K+ accumulation in roots and shoots. According to the results, no significant differences were recorded among the populations in response to the moisture treatments except chlorophyll content (P<0.05). The effect of moisture treatments on water use efficiency and physiological traits such as leaf osmotic potential, relative water content of leaves, total chlorophyll, chlorophyll a, chlorophyll b and Na+ in the root were significant (P<0.01). In addition, the effect of moisture treatments on leaf potassium was significant (P<0.05). Drought stress had no significant effect on other traits, including root osmotic potential, leaf Na+ and root K+. Effects of drought stress on morphological traits including shoot dry weight, root dry weight, total dry weight, and root to shoot ratio were significant (P<0.001). The interaction effects of population and moisture treatments on morphological characteristics were not significant.

A proper utilization of rangelands could result in preventing degradation, maintaining desirable species and improving range condition, leading to longterm and economic production. This research was aimed to investigate the allowable use of Stipa hohenckeriana in Kordan rangelands. In this study, a reference area of one hectare was selected and fenced in the first year of the study. Treatments included four harvesting intensities of 25, 50 and 75% and 0 (control group). Finally, data were analyzed using split plot design in time with 10 replications for each treatment. Data analysis was performed by SAS software. Results showed that the effects of harvesting intensity, different years and their interactions on the forage production were significant at 1% level of probability, indicating that in different years, production rate varied with varying climate conditions. According to the results, an allowable use of 25% is recommended for Stipa hohenckeriana in the study area. The recommended allowable use can be used in determining the allowable use for the study area and areas of similar climate, along with information from other plants.

Exclosure is the prevention of livestock access to all or part of the rangeland for one year or a few consecutive years, performed with different goals. This research was aimed to investigate the effect of exclosure on soil physical and chemical properties as well as three main elements of N, P, and K in Nazarabad region, Karaj. Soil sampling was performed in both sites of exclosure and grazing. Soil samples were taken from the beginning, middle and end of the four transects, established in each region, at two soil depths of 0-20 cm and 20-80 cm using systematic random sampling. The following soil properties were measured in the lab: pH, EC, organic matter, saturation percentage, and N, P, K. According to the obtained results, the effect of exclosure on soil N, P, and K was significant; however, exclosure had no significant effect on pH, organic matter and saturation percentage. Overall, our results clearly showed the positive impact of exclosure on soil physical and chemical properties.

Knowledge of forage quality is of paramount importance for livestock and rangeland management. For this purpose, the forage quality of range species was investigated in summer rangelands of Saraliabad, Golestan province to meet daily animal unit requirement. In the present study, 12 rangeland species including Achillea millifolium, Agropyron trichophorum, Centurea zuvandica, Crepis khorassanica, Koeleria cristata, Medicago sativa, Poa angustifolia, Taraxacum brevidens, Thymus transcaspicus, Tragopogon graminifolius, Trifolium repens and Artemisia aucheri were sampled at three different phenological stages (vegetative, flowering and seeding) in 2009. In each stage, three samples and for each sample three individuals were cut. Then, forage quality indices were calculated. Results showed that the crude protein values at all growth stages were higher than the critical level (7.0%) to meet daily animal unit requirement. In addition, dry matter digestibility values in vegetative and flowering stages were higher than the critical level (50%) to meet daily animal unit requirement, contrary to the seeding stage. Metabolisable energy values in vegetative stage were higher and in flowering and seeding stages were lower than the critical level (8Mj) to meet daily animal unit requirement. Our results clearly showed that the forage quality of range species varied at different growth stages, indicating that daily animal unit requirement need be determined based on forage quality. The results of this study could be used in determining the daily animal unit requirement in different years since measuring forage quality is costly.

This research was aimed to investigate the potential of four halophytes from the Urmia Lacke including Salsola dendroides, Salsola nitraria, Salsola iberica and Halocnemum strobilaceum as soli phytodesalination. For this purpose, soil samples were collected from two soil depths of 0-15 and 15-30 cm inside the ecological patches as well as around it. Our results clearly showed that the studied halophytes could reduce the amount of Na+, Ca2+, and Mg2+ significantly in the first soil depth (p<0.01). However, in the second depth, less affected by the root of species, there were no significant differences in the amounts of these cations in the soil of inside and outside the patches. The absorption of Mg2+, Cl-, Ca2+, Na+ and K+ by underground and aboveground biomass was also investigated. The results of mean comparisons showed that Salsola nitraria and Halocnemum strobilaceum accumulated the highest concentration of magnesium and chlorine in each gram of dry weight biomass. Also, the studied species showed no significant difference in SAR. The amount of these elements were compared in the roots of two species having the highest salt accumulation in aboveground biomass, and the species accumulating lower levels of these elements in roots was introduced. Overall, Halocnemum. strobilaceum showed the highest potential in absorbing salt through roots (soli phytodesalination) as compared to the rest of the species and its cultivation could be recommended for soil improvement and forage production in saline lands.

Livestock is one of the components of rangeland ecosystems. Different grazing behaviors would be observed according to the climatic conditions, the type of livestock and vegetation. Knowledge of livestock grazing behavior on rangelands could be useful in the planning and utilization of rangelands. For this purpose, in this study, the grazing behavior of sheep in the steppe rangeland of Saveh was investigated. Initially, a three-year-old ewe was selected, then, using a geographic positioning system (GPS), the path of movement, the time of arrival and departure of livestock, time of rest and movement speed were recorded. Data were entered into the GIS and statistically analyzed using two-way analysis of variance. Results showed that, except for the livestock average speed, there was no significant difference among the measured parameters of grazing behavior during the four years of study. The time spent for movement and rest in different months of the grazing seasonshowed significant differences, while the length of the grazing path had no significant difference during different months. The highest time spent for movement and rest was attributed to May, although the grazing distance in May was not significantly different from other months, indicating the presence of more and better forage for grazing in this month. The lowest average speed of livestock was recorded in May. The most covered distance by sheep occurred in slope gradient ranging from 0 to 8% with dominant cover of Artemisia sieberi and Salsola laricina. Generally, it could be concluded that livestock grazing behavior and rangeland management could be better evaluated using GPS technology and GIS.

Studies on vegetation changes in rangelands, under grazing and exclosure conditions are important in planning range management programs. This research was aimed to investigate the changes in vegetation inside and outside three exclosures of Maraveh tapeh during 1997-2005. The canopy cover was measured each year, in several permanent plots, inside and outside the exclosure. To study the effects of precipitation on the changes of cover, the correlation between canopy cover of species and vegetative forms inside the exclosure and the precipitation of months and different vegetative stages were calculated. Results showed that total canopy cover in 2005 was significantly higher than that of 1997, both inside and outside the exclosure, mainly due to the increased cover of annuals. On the contrary, the cover of perennials decreased inside and outside the exclosure. Reduction in the cover of perennials was mainly related to grasses. In the last year of study, compared to the first year, total cover of class II species reduced drastically contrary to the cover of class III species. Although changes in canopy cover were influenced by precipitation, correlation coefficients were just significant for total canopy cover and vegetation cover of perennials. However, exclosure cannot be used as a method of range improvement in these rangelands. For rehabilitation of these areas, direct human intervention is necessary.

In the present study, the effect of soil factors on above-ground vegetation and soil seed bank diversity under grazing and exclosure conditions was studied. Soil sampling was done in winter 2010 using randomized systematic method along four transects in the grazing and exclosure areas of Vaz watershed. Along each transect, 10 plots of 1m2 were established and soil samples were collected from a depth of 0-10 cm for seed bank and physico-chemical studies. Vegetation cover was measured in each plot in late spring of 2011. Soil factors such as porosity, bulk density, relative humidity, EC, pH, nitrogen, organic matter, and stone percentage were measured. Shannon and Simpson diversity indices were calculated for above-ground cover and soil seed bank and the most important factors influencing on the diversity were specified using multiple linear regression by backward elimination method. Results showed that the porosity, bulk density and organic matter had the greatest effect on the diversity of seed bank in the exclosure area. On the other hand, EC, nitrogen, organic matter, soil bulk density and porosity were the most important factors affecting the seed bank diversity of grazing area. According to the obtained results, organic matter and nitrogen were the main factors affecting the plant species diversity in the exclosure area, while in the grazing area, physical parameters such as bulk density, porosity and stone percentage had the highest impact on species diversity.

This research was aimed to determine the nutritive value of Cenchrus ciliaris, as one of the dominant range species of Bushehr province, as well as studying the changes during the growth stages. The study was conducted in three rangelands (Gomaroon, Kaki and Bashi) during December 2009 to May 2010. Sampling was performed randomly at vegetative, flowering and seeding stages and 10 samples were collected from each area. Then, samples were dried and ground to measure DM, CP, Ash, EE, NDF, ADF, ADL, GE, Ca, P, K, Mg, Na, Fe, Mn, Zn, Cu, DMD, OMD and DOMD in the laboratory. A completely randomized design with three treatments (stages) and three replications (areas) was used for statistical analysis. Results showed that NDF and ADF increased with the growth progress but CP, P, K, DMD, OMD and DOMD decreased significantly (P<0.05). The CP content of C. ciliaris, measured at vegetative and flowering stages, can supply the maintenance requirement for a 50-kg mature sheep, a 50-kg mature ewe in the first 15 weeks of pregnancy, and a 40-kg goat. The content ofCa, K, Mg, Na, Fe and Mn, measured for C. ciliaris at different growth stages, were more than critical level for sheep and goats; however, the content of P and Zn at three stages, and the content of Cu (except vegetative stage) were less than critical level. Totally, C. ciliaris is suitable for grazing livestock, especially at vegetative and flowering stages, and if possible, it should be proliferated in similar rangelands.

Determining land capability based on land suitability, climatic characteristics, and soil physical and chemical properties is considered as a method of achieving sustainable management. In this study, FAO model was used to determine land capability. To describe the spatial results, Geographical Information System (GIS) was used. Spatial data, as maps, and descriptive data, as database table, were entered into the GIS environment. The results of current land suitability model for irrigated agriculture and garden land use showed that 64.5% was in N2 class, 17.86% in N1 class, 17% in S3 class and 0.64% in NR class. For dry farming land use, 64.5% was in N2 class, 18.86% in S3 class, 17% in S2 class, and 0.64% in NR class. For rangeland use, 32% was in S3 class, 32.5% in N1 class, and 35.5% in NR class. For forest land use, 64.5% was in N1 class and 35.5% in NR class. From overlaying the current land use map with the current land suitability map, it was found that only 25.5 % of irrigated agriculture land use, 82 % of dry farming land use and 30.3% of rangeland use were consistent with their land suitability map, being exploited properly

Rangelands are one of the major sources of forage production in the country and in addition to its effects on the production of livestock products, a large population is dependent on rangelands because of animal husbandry. Since the government applies management on rangelands through range management plans, therefore, in this study, direct and indirect effects of management variables on range condition and trend as well as rangeland production were investigated by selecting three range management plans at three levels of successful, moderately successful and unsuccessful in Kerman, Kermanshah, Mazandaran, Khorasan Razavi and West Azarbaijan provinces. Management variables were included as follows: the accuracy of rangeland and livestock data, project compatibility with natural conditions, beneficiarie's conditions, funding and the capabilities of human resources, predicting the executive and beneficiarie's obligations, executive calendar, and active supervisors. According to the results of rank correlation by Spearman, variables of range condition and trend as well as rangeland production had a high rank correlation together.According to the results of path analysis, variables including the accuracy of rangeland data, project compatibility with the capabilities of human resources, predicting the executive obligations, active supervisors, and beneficiarie's obligations were the factors which improved range condition and trend as well as rangeland production. Due to the negative impact of variables including project compatibility with funding, project compatibility with beneficiarie's conditions, and executive calendar on range condition and trend as well as rangeland production, these variables must be revised and their function need be evaluated. In addition, it is emphasized that greater sensitivity is required in planning for the future due to the negative effect of these variables. Other variables had no favorable or negative effect directly; however, they affected range condition and range trend as well as rangeland production indirectly.

Investigation on the vegetation cover of rangelands under grazing and exclosure conditions is important in improvement of range management. Therefore, this research was aimed to investigate the effect of exclosure on production, density, frequency, importance value and vitally of Artemisia sieberi as the most important species of steppe rangelands of Iran. The study was conducted in Nodushan rangelands of Yazd province under grazing and exclosure conditions. Sampling was done randomly in both grazing and exclosure areas, with 10 transects and 40 quadrates of 1m2. In addition, 30 individuals of Ar. sieberi were selected randomly in each area and plant height, maximum and minimum diameter, canopy caver, vitality and dry matter production were measured. According to the obtained results, the studied species showed no significant differences for production, average diameter, height and canopy cover percentage. However, the vitally of Ar. sieberi showed significant differences between grazing and exclosure areas. The results of importance value indicated the increased relative importance of Ar. sieberi under moderate grazing intensity. The distribution pattern of Ar. sieberi under exclosure was uniform while under grazing condition a clumped distribution pattern was observed.

Precipitation is one of the factors affecting vegetation. Nowadays, satellite images are broadly used for monitoring the effects of precipitation variations on the vegetation changes. The aim of this study was to investigate the relationship between vegetation dynamic and precipitation variations using NOAA AVHRR images during the period of 1982-2006. Precipitation maps were created using the inverse distance weighting interpolation (IDW) method and time intervals of precipitation data. The study area was a forestland beside Caspian Sea, four rangeland vegetation types with grasses and shrubs, farmland areas and urban areas, located in Ardabil and Guilan provinces. To monitor the relationship between the precipitation and vegetation changes, the linear regression (NDVI, Y & Rainfall, X) method was employed. Based on the results, depending on the precipitation time, plant species, and growth form, the effect of precipitation on vegetation was different so that no significant relationship was observed between vegetation and precipitation in forestlands, farmlands, and urban areas. The highest correlation coefficient between spring precipitation and vegetation was related to the rangelands. In grassland areas, the correlation coefficient was higher than that of shrublands, whereas the reaction of grasslands to precipitation in various parts was different.