فصلنامه تحقیقات مرتع و بیابان ایران
سال هجدهم شماره 1 (پیاپی 42، بهار 1390)

Importance of production information in range management has caused researchers be seeking to find suitable methods for yield estimation. As clipping and weighing method has been recognized as a time consuming, high cost and destructive method, researches have been conducted on indirect methods. Estimating yield from cover data can be considered as an important method. In the present study, relationship between cover and yield was determined at first. Then investigation was done to find how cover data can be used to estimate production using a double sampling procedure or pooled equation. Research was carried out in two rangelands of Manuka (a semi-arid rangeland) and Conservation (as an arid area). Double sampling was formed by clipping and weighing method as direct sampling and foliage or canopy cover measurement as indirect sampling for each group of species. The number of paired of direct and indirect sampling based on time consumption and accuracy were 4, 6, 8, 12, 16, 20, 24, 28, 32, 36 and 40. SPSS was used for data analysis. Data were collected during 2 or 3 years in different seasonal conditions of fair, poor and good. The results showed the possibility of estimating range production from cover measurement using equation based 8 to 12 paired direct and indirect sampling. Correlation between cover and yield was higher for all collected data in both rangelands of Manuka and Conservation. According to the results, cover data can be used in both models of double sampling or pooled equation for accurate yield estimation.

Agropyron deserterum and Ag. elongatum species have a high value for both fresh and dry forage and because of high production and top acceptance by livestock they have specific value in the beginning of the growth season for livestock grazing. This research was conducted to study the effects of salinity stress on the mentioned species in germination and vegetative growth stages. A completely randomized design including five levels of 0, 100, 200, 300 and 400 mM NaCl and CaCl2 with 4 replications was used. Seeds were sown in laboratory and germination percentage, germination velocity, vigor index, plumule and radicle length and seedling dry weight were calculated. In greenhouse condition, shoot and root length, seedling dry weight, dry weight to fresh weight ratio, leaf area and specific leaf area were measured. According to the results, in both studied species germination percentage, plumule and radicle length, seedling dry weight, leaf area and specific leaf area were reduced with increase of salinity. The results showed significant differences between two species for germination percentage and germination velocity (P≤0.01). In both germination and vegetative growth stages, Ag.elongatum was more salt tolerant than Ag.desertorum. The results indicated that Ag.elongatum was more salt tolerant species than Ag.desertorum and it can be recommended for cultivation in moderate saline rangelands.

This research was performed to determine the nutritional value of a halophyte species, Halostachys caspica in three different phonological stages including primary growth, flowering and seed ripening in three different sites i.e, Qom, Yazd and Urmia provinces Plant sampling was completely randomized and crude protein, ether extract, water percentage, acid detergent fiber, ash, dry matter digestibility and metabolism energy were measured by standard methods. Data analysis was done using SPSS software in a factorial design. According to the results, interaction effects of growth stages and different ecological sites showed a significant difference for most of the measured factors and they did not follow a regular trend. The results indicated that H. caspica had the highest forage quality in flowering (second stage) while with increase of plant age, crude fiber and ash increased in all the three studied sites. Growing in sever ecological conditions and having high forage quality, H. caspica may be considered for sustainable development plan in saline regions.

Soil temperature is one of the most important and effective factors influencing the establishment of vegetation in arid regions. Soil temperature is affected by several meteorological parameters. The study of air temperature, rainfall and sunshine hours can be useful to understand the variation of soil temperature. Soil temperature changes and rate of heat transport in soil profile are helpful for evaluating the amount of evaporation, plants water requirements, decomposition rate of materials, biological activities and the time of seed planting. The aim of this study is to evaluate the role of atmospheric factors in determination of the soil temperature. For this purpose, after collecting daily temperatures data of different soil depths (5, 10, 20, 30, 50 and 100 cm) in Yazd synoptic station for 2006, firstly, the effective meteorological parameters were analyzed and then soil temperature at this station was simulated by using sinusoidal changes pattern during the year. Finally, soil temperature variation curve at any depth was plotted and evaluated using the models obtained. Primary results showed that there was a significant relationship between precipitation, air temperature and sunshine hours. Measured and predicted values were evaluated in a coordinate system. The results showed that with increasing depth, the sinusoidal model predicted values underestimate. The results of calculating coefficients of Nash-Sutcliffe model efficiency (RNS2) showed that the estimated values by model for the different depths (5, 10, 20, 30, 50 and 100 cm), compared to the measured ones had efficiency coefficients as 0.92, 0.91, 0.93, 0.92, 0.94 and 0.96, respectively. Since (RNS2) value varies between- ∞ to 1, and when its value is equal to 1, the model has maximum efficiency, so, sinusoidal equations have good capability for predicting temperature variations in soil different depths.

The current research was conducted at Qom Fadak Greenhouse to study the effects of different salinity levels on physiologic and morphologic characteristics of three rangeland species (Hordeum fragilis, Agropyron desertorum and Agropyron elongatum). A factorial experimental design based on completely Randomized Design with three replications was applied as the main factor included three rangeland species and the second factor included five salinity levels (0, 50,100,150 and 200 mMol NaCl). Salinity treatments were applied for 66 days and 27 variables were evaluated during the experiment. Results of analysis of variance showed significant differences among studied species and also different salinity levels. According to the results of means comparison test in 15 treatments (interaction effects of species and salinity), the highest RWC was observed in treatments of control (0 mM NaCl) and 50 mM NaCl in all three species and the lowest RWC was recorded at 200 mM NaCl in two Agropyron species. As a result, reduction in RWC was identified as plant response to salinity stress. The highest content of total chlorophyll was observed in control treatment and in two Agropyron species while the lowest content was recorded at 200 mM NaCl in all three species. With increase in salinity level up to 200 mM NaCl, soluble carbohydrate content increased. The highest percentage of proline was observed at 200mMol NaCl and in all three species. According to the results, threshold of salinity tolerance for Ag. elongatum, Ag. desertorum and Hordeum fragilis were determined 150, 100 and 50 mM NaCl respectively, and Ag. elongatum was identified as the most salt tolerant species in this research. A significant positive correlation was observed among growth parameters while correlation between growth parameters and carbohydrate content and percentage of proline was significantly negative. Total chlorophyll content showed a significant positive correlation with RWC and a significant negative correlation with WSD, soluble carbohydrates content and percentage of proline.

Seed dispersal distances of mother plant is a basic aspect in plant life history, and have great effects on plant ecology, evolution and conservation. Seed dispersal modes of species can often be recognized by morphological characteristics of fruits and seeds. A laboratory experiment was conducted on seeds of 24 Northern Khorasan rangeland species during 2008. The size of seeds was measured by digital caliper with a precision of. 0.01 mm (operating instruction in resolution 0.01 mm), and the seed's shape were observed by binocular and drown by hand in scale of 30-80 times. Seeds were categorized in five categories based on their shapes and morphological traits namely, Nutrient Containing Structure (i.e. Artemisia seiber), Balloon Structure (i.e. Agropyron trichophorum), Elongated Appendages (ie. Salsola arbusculaformis), No Appendages (i.e. Stachys inflate and Iris songarica) and other Specializations (i.e. Kochia prostrate). According to the results, balloon structure category was identified as the most common seed dispersal mode in the zone of Northern Khorasan (with 9 species) which let the wind disperses the seeds easily. The elongated appendages category was placed in the next group and other categories owned third place. It can be concluded that balloon structure has provided the most suitable dispersal system for the seeds studied in Northern Khorasan rangeland.

Autecology is the study on behavior and performance of a plant species and its relationship with other living and non living components of a habitat. These kinds of studies provide basic information for management in rangeland ecosystems. In the current research, autecology of Lolium perenne was studied in Mazandaran province. Geographical distribution, phenology, companion species, dryness index, edaphic and climatic parameters were considered as effective factors on distribution of Lolium perenne. According to the results, the altitude range for the mentioned species was from -22 to 1700 m above sea level. This species is frequently found in different places like road sides, irrigation canals, clay slopes, rocky and sandy hills, and also as a weed in farm fields. Presence percentage in lowlands was also more than that in uplands. Lolium perenne is resistant to cold and harsh conditions and grows mainly in humid to sub humid climates and alpine to Mediterranean and semi-arid habitats. Our results indicated that Lolium perenne prefers clay, clay loam, loamy sand, silty clay loam and silty clay soils. These observations show that Lolium perenne can grow in a wide range of ecological conditions.

The aim of this research was to evaluate the effect of climatic factors on vegetation in rangelands of Zagross with normalized difference vegetation index (NDVI) derived from Advanced Very High Resolution Radiometer (AVHRR) sensor, and climatic data. The study area was rangelands of Zagross with 51-75, 26-50 and 10-25 density. Satellite images and climatic factors were respectively studied from January to October 2006 and from September 2005 to October 2006. Effects of seven monthly climatic variables (precipitation, temperature and relative humidity (maximum, mean and minimum) were studied on monthly NDVI. Zoning was performed by geostatistical method and Multivariate Ordinary Least Squares regression (MOLS) was applied to study the effect of climatic factors on vegetation changes. According to the Results CO-Kriging was identified as the best method for zoning, and Inverse Distance Weighting (IDW) only in mean temperature showed a better distance. Vegetation responses to precipitation of last two months, and temperature and relative humidity of last one month. Results of MOLS showed higher correlation in rangelands with a density of 51-75 %, but generally, correlation was low in rangelands with a density of 10-25 %, that can be due to the low altitude from sea level, effect of soil background and agricultural field margins. Also, low height in rangelands with a density of 10-25 % increased the temperature and transferred the start of leaf greenness to March, while in rangelands with a density of 51-75 % greenness started in May. The highest and lowest R2 values were calculated as 0.6478 for dense rangelands in May and 0.136 for low density rangelands in August.

Accurate and up-to-date global land cover data sets are necessary for various global change research studies including climatic change, biodiversity conservation, ecosystem assessment, and environmental modeling. The aim of the present research was to study change detection of vegetation during the grazing season using multi temporal data of WiFS in Semirom region. Various preprocessing, including geometric correction were applied using topographic maps of 1:250000 with an RMSe 0.35 pixel for sensor IRS-WiFS. The atmospheric and topographic corrections were carried out using dark-object subtraction method and the Lambert method. Field data collection was started on June 2005 on 800,000 ha. Multi-temporal data of IRS-WiFS sets were used for this study. Image processing including FCC, PCA, vegetation indices and supervised classification were employed to produce the vegetation canopy cover map. Various vegetation types were sampled using stratified random sampling method. twenty random sampling points were selected and canopy cover percentage was estimated. Digital data and the indices maps were used as independent data and the field data as dependent variables. The produced models were processed and then resulted images were categorized in 5 classes. Also post classification method was used to determine change detections. Finally the produced maps were controlled for their accuracies. The results confirmed the high correlations of used WiFS indices with field data. In the current study, more than 30 percent of the study area has been affected during the grazing season. Also the NDVI, SAVI and DVI indices which employ RED and NIR bands had relatively highly correlations with rangeland data. Result showed vegetation maps produced with IRS-WiFS data set had very high accuracy.

In order to determine the best genotype for range improvement in Tehran province, Iran, 19 ecotypes of Agropyron cristatum were sown using randomized complete block design with three replications under irrigation and dry land farming system during 2006- 2007. Data were collected and analyzed for dry matter (DM) yield, flowering and pollinating date, plant height and 5 quality traits as: dry matter digestibility (DMD), water soluble carbohydrates (WSC), crude protean (CP), total ash, and acid detergent fiber (ADF). The results showed significant difference at 1% level of confidence for yield and morphological traits while no significant differences were observed for forage quality under two different cultivation conditions. The difference between ecotypes and environment-ecotype interaction effecets were significant for all traits of the species. Ecotypes 208P8 and 4056P4 with average values of 1240 and 1336 Kg/ha had higher forage yield in irrigation condition while in dry land condition, forage yield of ecotypes 619M and 4056P4 with average values of 791 and 901 Kg/ha were maximum. According to the results, ecotypes 1722M (Gorgan), 208P8 (Esfahan) and 4056P4 (Gorgan) with average yield value were identified as the best ones for both yield and quality traits in studied cultivation conditions to be introduced for cultivation in dry land faming in Tehran province. DM yield had positive correlation with plant establishment. WSC had positive and negative correlation with DMD and CP, respectively. The relationship between DMD and ADF was negatively significant.

Current events indicate that the country's Natural Resources are being destroyed and with the present utilization approaches, this trend would be continued. A research study was conducted to determine effective socio-economic factors on degradation of Natural Resources in Tehran province. In the current study, an index was applied to determine the degradation considering forage and forest production. To achieve this goal, data were collected from experts and users of Natural Resources through questionnaires and interviews and relationship between the data and the degradation index was determined. The research was conducted based on the study of documents, archival data, and field works. Range condition of the province was compared during 1955 – 2001 in view of area change. Our results showed that decrement of forage production was higher in mountainous rangelands than that in plain areas (steppe and semi-steppe). In plain areas, land use change of Natural Resources to constructed and agricultural area was identified as the most important destructive factor. Staff and facilities deficiency for Natural Resources control was also known as the most important organizational factor. Based on statistical analysis, there was a strong inverse relationship between the size of posturs’ agricultural areas and the rate of rangeland destruction. According to the results, implementation of land use planning and management is important for Tehran province and land use change of natural resources was identified as an important destructive factor.

Salinity is one of the most important causes in reduction of agricultural products and depletion of natural vegetation in many parts of the world, like Iran. Sesbania aculeata is a palatable forage and relatively salt tolerant species from Fabaceae family that can be used for reclamation of semi- saline rangelands. The study was performed to evaluate the salinity resistance of this in view of ions accumulation and anatomical changes. S. aculeata seeds were planted in sand under greenhouse conditions and irrigated with Hougland nutrient solution. A completely randomized design including three levels of salinity (control, 75 and 150 mM NaCl) was applied and plants were harvested after two months. According to the results, fresh and dry weight of roots and shoots and relative water content were decreased under salinity. With increment of salinity level, Na+ and Cl- accumulation increased in all organs of plants which were more obvious in shoots. Furthermore, the potassium concentration and K+/Na+ ratio decreased in shoots and roots while total amino acids and soluble carbohydrates increased in plants in response to the salinity. Salinity also increased the palisade parenchyma cells thickness and total thickness of leaves, while spongy parenchyma cells thickness decreased under salinity. In addition, ratio of cortex to stele decreased in roots of plants grown under salinity. The results reveal that S. aculeata probably accumulates Na+ and Cl- mostly in vacuoles and amino acids and sugars in cytosol of thick leaf cells with palisade parenchyma through which osmotic adjustment and water absorption by plants is done with minimum energy. Increase of stele area in comparison with cortex in root may also facilitate water uptake under salinity.