فصلنامه تحقیقات مرتع و بیابان ایران
سال هجدهم شماره 2 (پیاپی 43، تابستان 1390)

The protection, improvement and development of renewable natural resources especially for vegetation need a comprehensive recognition of natural resources. To achieve some part of these objectives, the national project of autecology was carried out in Iran. In Qom province, autecology of Stipagrostis plumosa, an important rangeland species in desert, semi-desert and steppic regions, was studied.In this research, geographical distribution of the species in the province, morphology, phonological stages, companion species, reproduction and establishment methods were determined. Soil study, geology and climatic condition were also investigated. With regard to the wide distribution of Stipagrostis plumosa in the province and variations of climatic and ecological factors, three sites were considered. The results showed that Stipagrostis plumosa was found in silty- loam, loam- sand, loam- clay and sandy soils as a dominant species and with increase of clay percentage, canopy cover was decreased as it was not seen in soils abundant of clay. This species was also highly resistant to soil salinity and lime as tolerated the EC between 0.27 to 2.89 milmohs/cm and %13 to % 24 of lime. It was found in altitude of 900 to 1650 meters above sea level. Its height was between 12 to 35 cm and partly about 50 cm in suitable condition. It had bunch stems and scattered roots. In flowering stage, the ratio of root to shoot length was about 1.25 and ratio of root to shoot weight was about 0.47. The main activity period of this species begins generally from mid February and ends in late June with the seeds bloom and seed dispersal. Reproduction by seed is conducted appropriately while in areas with high grazing pressure asexual reproduction is done. Resistance to unfavorable environmental conditions and drought, high tolerance to different soil conditions, high resistance to grazing and suitable regeneration could be considered as the main reasons of the wide distribution of Stipagrostis plumose in Qom province.

To study soil salinization and its amplitude due to the planting of Haloxylon ammodendron in Segzi plain of Isfahan, ordination method was used. The study was performed through stratified random sampling. Six regions were separated on the basis of different physiognomy and the year of Haloxylon ammodendron planting (successful and unsuccessful regions). In each region, 10 coeval individuals of Haloxylon ammodendron were selected, and plant characteristics including, height, canopy cover area, canopy cover perimeter, canopy cover diameter and basal area were measured. Three profiles were also dug in each region and five chemical soil properties i.e. EC, Na+, Cl-, K+ and SAR were measured in five horizons. Data were analyzed by means of ordination method. The results indicated that soil salinization was extremely high in successful planting regions of Haloxylon ammodendron where there was no limitation for root extension. Consequently, in these regions, the absorption of water and minerals, the growth of plant characteristics and finally the amount of litter fall to the soil surface were significantly higher than that in unsuccessful planting regions of Haloxylon ammodendron. Hence the role of Haloxylon ammodendron in soil salinization of its stratum was proved. On the other hand, the results showed that the range of soil salinization was only restricted to the first and second horizons (0-30 and 30-60 centimeters from the soil surface) and other horizons had not been affected by the growth of Haloxylon ammodendron.

The large scale degradation of rangelands in Iran can be largely attributed to overgrazing. So investigation on the effects of grazing on vegetation parameters is vital to control the rangeland ecosystems degradation. The object of this study is to investigate the effect of heavy, moderate, and light grazing intensity on production, canopy cover, litter, stone, grovel and bare soil in steppe zone of central Iran (Nodushan summer rangelands). For this research, stratified systematic-random sampling was use in a completely randomized block design. On each plot of 2m2, canopy cover percentages and density of plant species, dry matter of palatable species, litter, stone, grovel, and bare soils were estimated. Classification of the sampling site was based on TWINSPAN (Two Ways Indicator Species Analysis). In order to study the effects of grazing intensities on vegetation parameters and their relationships with the distance of watering points, ANOVA and Pearson’s correlation were employed. By using of TWINSPAN, the samples were classified in to, 3 groups. Results were shown that canopy cover percentage of palatable plants and production at different grazing pressure were significant (P<0.05). Litter percentage, stone, grovel, and bare soil percentages of heavy grazing was significantly different with moderate and light intensities of grazing (P<0.05). Canopy cover percentage of unpalatable plants and density of plants were not significant at three different grazing pressure (P>0.05).

Rangelands play a key role in country's economy not only for livestock grazing but also for soil and water conservation and other services. This research was based upon a national plan of rangeland monitoring performed in different climatic regions of Iran. Three sites including Asalmeh Bajgiran, Tavakal bagh Quchan and Shah jahan Esfarayen were selected based on the vegetation cover which represents a part of vegetation of mountainous rangelands in north Khorasan. The experiment was carried out on six linear transects, each transect included ten quadrates of 1.1 m2 and canopy cover, density and plant production were monitored during the period of four years (2004 to 2007). Average of the canopy cover in the mentioned sites were 69.94%, 41.38% and 48.44% respectively, containing perennial grasses, shrubs, grass-like species, and annual or perennial forbs. Average of the annual production was obtained as 654, 356 and 506 (kg/ha/year) respectively. In Asameh rangeland, there is no spring for drinking water and that is why livestock grazing is light with a good condition of vegetation. In Tavakal Bagh, grazing time is longer due to the vicinity to the village. In Tavakal Bagh and Shah Jehan Esfarayen early and heavy grazing are observed. Therefore, with regard to the same precipitation, it could be concluded that grazing is the effective factor in reduction of the range lands production.

Aim of this study was to introduce of the functional threshold by ecological process changes along grazing gradient to determine destroyed area. In order to prove the existence of a threshold, two linear models and three nonlinear models (exponential curve, a piecewise regression and a sigmoid logistic) were fitted on stability, infiltration and nutrient cycling data. Two nonlinear models (exponential curve and a piecewise regression) provided a much better fit to the data than the linear models. It is the evidence of threshold along grazing gradient. Results also showed that ecosystem function descended near the water point that it needs special attention of the managers. The passing of the structural threshold, increase of invasive vegetation and animal trampling were identified as the main factors in the decline of ecosystem function near the water point and occurrence of functional threshold. According to the results, the recognition of the threshold is suggested for rangeland ecosystem because defining the threshold will help land managers to prevent the occurrence of undesirable states and promote for sustainable management of rangeland ecosystems.

Herding system in countries like Iran with ancient herding celebrity is very important. The system should be recorded for the next generation to remind them of what their ancestors have had. This research was conducted by new techniques such as GPS to track the system at Hosesoltan range adjacent to Hosesoltan Lake for three years, 2006 to 2008. A GPS was installed on the back of a three years ewe and her movement such as departure from resting area to rangelands and its reverse, course time of grazing, rest and moving without grazing were recorded. Maximum and minimum speed of the animal also was measured. This survey suggests that the system is smart enough in terms of limitations and available sources.

Land use utilization based on its capability and susceptibility is necessary for proper management of different regions. In this regard, the conversion of rangeland areas to dry farming and its consequent effects on soil erosion is a crucial problem that has to be carefully investigated. The present study therefore attempted to study the runoff and sediment rates in experimental plots located in two land uses of rangeland and dry farming lands with a slope of 5 percent by using rainfall simulator. The research was conducted during summer 2009 in Tiregan watershed located in Daregaz Township, Khorasan Razavi Province. The experiments were taken place through simulation of rainfall with intensity of 1.7 mm min-1 in two upper and lower positions, in eastern and western aspects of the slope in both the land uses. Afterwards, the runoff threshold was determined and the runoff samples were collected in small containers. The results of the study showed that the average runoff threshold in rangeland was 3.36 minutes earlier than that occurred in dry farming land. The runoff volume in rangeland plots was also 2.3 times more than dry farming land did. The sediment yield in the upper position in eastern aspect of rangeland treatment was lesser than dry farming treatment did. The difference was not significant in other treatments. The turbidity rates were also significantly more in dry farming lands compare to what recorded for rangeland areas.

The amount of water infiltration into the soil depends on many factors such as soil texture, soil structure, initial moisture content, soil bulk density, canopy cover, plant age, organic matter and the plant succession stages. Livestock trampling and reduction of the vegetation cover due to the overgrazing are considered as the most important factors affecting the amount of infiltration in rangelands. Winter rangelands of inchehbroon with dominant species of Halocnemum strobilaceum are introduced as the halophyte rangelands in Golestan province. Distribution pattern of plant species in these rangelands is spots surrounded by bare soil in the form of islands. In this study, heavy grazing area was determined and for measuring water infiltration into the soil, paired rings (dublering) were used. Parameters of infiltration intensity, final infiltration, cumulative infiltration and infiltration time were investigated in vegetation types of Halocnemum strobilaceum, Aeluropus lagopoides and bare soil. The results of the data analysis showed that there were no significant differences in infiltration intensity and infiltration time among Halocnemum strobilaceum, Aeluropus lagopoides and bare soil while final infiltration and cumulative infiltration significantly differed.

Due to the land use changes like increased acreage for agriculture, digging deep and semi-deep wells has increased rapidly in recent decades in Marvast area as these wells are the main source of water supply at the present time unlike the past which rivers and aqueducts had this role. The main purpose of this study was to monitor land use changes on soil salinity using satellite images and GIS. Our other purpose was to investigate soil salinity changes in each land unit. With using satellite information from 1984 and 2002 years and proposed method for mapping soil salinity, land use and soil salinity maps were produced and then land use and soil salinity changes were studied. The study area had a total land area of 88980 hectares in Marvast, Yazd province. Results showed that land area of playas, deserts and rangelands respectively decreased to 7.8, 2.9 and 1.5 percent versus increase of agriculture and urban land area to 77.8 and 153 percent respectively. Also during this period, sever increase, increase and decrease of soil salinity was respectively recorded for playa, agricultural and rangelands, and deserts while no changes was detected for other regions. According to results, under ground water resources and saline waters of playas have undergone serious changes as with increase in average soil surface salinity, the ecosystem has shown negative changes.

The genus of Elymus is of important grasses for forage production and soil and water conservation in Iran's rangelands. It has high preference value for livestock grazing because of the high production and high acceptability. Important species of this genus show different tolerances to drought. In order to determine the reactions of 14 accessions of Elymus hispidus and Elymus pertenuis to drought stress, a factorial experiment was conducted using completely randomized design with three replications in a standard germination test in 2008, Shiraz, Iran. Polyethylene glycol 6000 was used at 4 levels (0, -8/0, -9/0- and -1 MPa) as different osmotic potentials. Data were collected and analyzed for germination percentage, speed of germination, root length, shoot length, seedling length, root / shoot length ratio, seedling weight and seed vigor index. The results showed significant differences among accessions, drought effects and interaction effects of accessions* drought for all the traits. However, there were no significant differences between means of two species for all traits except seedling weight. In both species, all traits except root / shoot length ratio were decreased by increasing osmotic potential. In contrast, means of root / shoot length ratio was increased by drought stress. The effect of drought stress was higher on shoot length than those for root length, indicating that the sensitivity to drought stress of shoot length was more than root length. The results showed that some accessions within E. hispidus species as (Yasoj, Eghlid and Brojen) showed the maximum drought resistance in most of the seedling attributes. According to the results of Probit analysis, LD50 were estimated as -0.72 and -0.81 MP for E. hispidus and E. pertenuis, respectively.

Evaluation of changes in rangeland ecosystem after rehabilitation and restoration projects is important to determine the positive or negative effects of these projects. Parts of species composition in rangelands are in the soil seed bank as living seeds which are a potential for regeneration. Management and environmental factors may change the soil seed bank. This Study was carried out in mountain rangelands in Kabir watershed in Mazandaran province. A restoration project was done in this area 7 years ago and this study aimed to assess the effect of this project on soil seed bank. Soil was sampled random-systematically in control and restoration sites (210 samples) from 0-5 and 5-10 cm depths. Then seed bank composition was identified after seed germination in greenhouse. The results of this study showed that there were 38 species in soil seed bank whereas 71 species were existent in vegetation. Only 16 species were common between seed bank and vegetation. We found greater species diversity and richness in vegetation than that of soil seed bank. Only 18 species were common in the soil seed bank of control and restoration sites. Seventeen species were restricted to the seed bank of restored site. Among common species between soil seed bank of two sites, the project significantly influenced the seed bank of two species. Also, the restoration project significantly increased the richness and diversity of soil seed bank. Some species were unique to the specific soil depth. The results of this study showed that the soil seed bank would be altered by restoration and rehabilitation project and this depended on vegetation change due to restoration, type of treatment and time since project was performed.

In this research, deserts domain of Iran was studied and compared in view of the geological and climatological specifications.Geological deserts domain was made as digital maps with considering saline and evaporate formations which have been effective in their development. To determine climatological deserts domain, climatological factors including amount of precipitation, rainfall coefficient variation, rainfall irregularity coefficient, the average intensity of daily precipitation, annual average temperature and amount of evaporation were calculated for all studied stations. Using Geographical Information System (GIS), the isohyets digital maps were prepared for each factor. With overlaying layers, a transitional boundary was made through which non-desert areas were separeted from deserts. All (geological and climatological) desert units were set up on the country map with utilization of the coordinate system and georeference. According to the results, climatological and geological deserts respectively encompassed 42.5 % (700991 km2) and 12.6% (208041 km2) of Iran map. Each individual layer covered different desert area on the map. Crossing and matching of two layers (common parts of overlaying) was 22.6% of the geo-climatological deserts of Iran which indicates differences between spatial distribution of geological and climatological deserts.