فصلنامه تحقیقات مرتع و بیابان ایران
سال هجدهم شماره 4 (پیاپی 45، زمستان 1390)

This study was carried out to determine the effect of different NaCl and Na2SO4 concentrations, including (0, 100, 200, 300, 400 and 500 mM), on germination and initial growth of Seidlitzia rosmarinus. Germination percentage, germination rate, germination index, seed vigor index, radicle length, and plumule length were measured. Our results showed that the most of studied characters were severely inhibited at high concentration of NaCl and Na2SO4. The results revealed that the effects of the same concentrations of NaCl and Na2SO4 on radicle, plumule and plant length were significantly different, but germination percentage, germination rate, germination index and seed vigor index did not show significant differences. In general, the results indicated that Seidlitzia rosmarinus was more sensitive to Na2SO4 than NaCl and it could be considered as a chlorophyte halophyte.

In this research, the spatial patterns of shrubs were determined by using T-square distance method in protected and unprotected areas of Golestan National Park. The results indicated that the patterns of shrubs were clumped – regular and clumped – random in woodlands. There were numerous species of shrubs in protected area and the canopy cover of grasses and forbs were much higher under the shrubs than that of unprotected area. So the richness and diversity of the species were higher than the unprotected area. The dominant species of unprotected area was Ephedra distachya and the grasses and forbs had less contribution in vegetation of the area. Bare soil and rocks were appeared more frequently.

Salt and osmotic stresses are responsible for both inhibition or delayed seed germination and seedling establishment. Salts may affect seed germination by either restricting the supply of water (an osmotic effect) or causing injuries through involvement of their ions into the metabolic processes (ionic effect). The aim of the study was to determine the effect of salt and osmotic stresses on Agropyron cristatum and Agropyron elongatum seeds. In this respect, iso-osmotic solutions of sodium chloride (NaCl) and Polyethylene glycol 6000 (PEG 6000) under osmotic stress levels of (0, 4 and 8 bars) were applied to induce osmotic and ionic effects. The applied experimental design was completely randomized design with a three-factor factorial (2×2×3) arrangement in three replications and 50 seeds per replication. Germination percentage, germination rate, shoot length and vigor index showed significant reduction due to higher osmotic tensions on both Agropyron species. Only root length had no statistically significant difference between stress levels 0 and 4 bars. Iso-osmotic solutions of NaCl and PEG 6000 in A. cristatum did not show statistically significant difference, but in the case of A. elongatum significant differences were observed between these two iso- osmotic solutions. This study showed that PEG 6000 as an osmotic agent of salinity had more inhibition effect rather than ionic effect of Nacl. However, the toxicity of ionic effects was raised by increase of osmotic stress levels. This study showed that the tolerance of A. elongatum against salinity was more than A. cristatum species.

In the current study, some physiological responses of Kochia Prostrata to salinity stress were investigated. This species is native to Iran and could be used as forage for livestock. Plants were exposed to 0 (control), 50, 100, 150, and 200 mM NaCl. The experimental design was completely randomized design with 4 replications and 5 treatments. To prevent osmotic shock, the treatments were done gradually. After 21 days of the last salinity treatment, the plants were harvested and proline, glycinebetaine, soluble sugars, water potential and relative water content were measured. The result showed that in Kochia Prostrata, with an increase of salinity concentration up to 200 mM NaCl, proline, glycinebetaine and soluble sugars increased. According to the results, this plant tolerates the salinity through the synthesis of proline, soluble sugars and glycinebetaine as the mechanisms of salt tolerance. The high relative water content of the leaf (RWC) up to 150 mM and significant decrease of water potential also caused an increase of water use efficiency with low evaporation and transpiration from the leaves.

To identify destroyed area and to introduce a piospher, pattern of vegetation composition was considered at different distances from a water point.Therefore in 113 plots, species density and vegetation cover were evaluated.To identify the patterns of vegetation composition, Clustering analysis was applied on species density and vegetation cover and three distinct groups of vegetation composition were obtained. ANOVA analysis showed that three groups were different (p<0/01). By using DCA, relations between groups and species were evaluated. Result showed that there was a piospher on 300 m from water point. In this zone, vegetation composition extremely changed due to heavy grazing and palatable species were replaced by annual or perennial unpalatable species but with distance from water point, perennial and palatable species increased. Study of relations between vegetation compositions (was obtained by plant functional types) and grazing intensity showed that in addition of quantitative methods, qualitative methods such as vegetation composition and plant functional types could be an appropriate method to determine ecosystem condition in shrublands.

Environmental stress especially water deficiency (drought) is of the most important factors in arid and semi arid regions of Iran that hugely affects plant growth especially in germination and emergence stages. To find the effects of water stress on germination properties and early growth characteristics of three Bromus species (B. tomentellus, B. inermis, B. persicu), a Factorial experiment based on Completely Randomized Design with four replications was conducted. Water stress treatments included -3, -6 and -9 bars, also distilled water was considered as control. Germination percentage, root length, shoot length, seedling length, root to shoot ratio, seedling dry weight, seedling fresh weight, dry to fresh weight ratio, germination rate and seed vigor were examined as germination and early growth properties of understudied species. The results showed that increase of drought stress, especially when changing from -3 to -6 bars, significantly reduced all attributes. Seedling length and seed vigor showed more decrease. Among the species, B. tomentellus showed higher germination compared to the other species. It was cleared that -6 and -9 bars potentials could be considered as favorable water stress levels to evaluate the ability of the mentioned species for germinating under drought conditions.

This study was conducted to study the effect of seed dormancy breaking on seed germination of Caper (Capparis spinosa L.), in a completely randomized design with four replications. Treatments of seed dormancy breaking in Caper included: untreated seeds (control), scarification with concentrated sulphuric acid for 20 minutes, soaking in gibberellic acid (500 and 1000 ppm), Potassium Nitrate (0.3%), leaching for 12 hours and combined treatment (leaching for 12 hours and soaking in gibberellic acid (500 and 1000 ppm), leaching for 12 hours and soaking in Potassium Nitrate and scarification with sulphuric acid and soaking in gibberellic acid (500 and 1000 ppm). The results showed significant differences among seed dormancy-breaking methods. According to the results, the highest seed germination percentage of caper was observed in combined treatment (leaching for 12 hours and soaking in gibberellic acid 1000 ppm (98%) and leaching for 12 hours and soaking in gibberellic acid 500 ppm (75%). Our results showed that the treatment of seed leaching for 12 hours reduced the formation of mucilage around the seed and caused an increase in seed germination. Moreover, application of gibberellic acid or Potassium Nitrate could be just useful when the mucilage concentration of the seed coat is reduced by leaching.

Kochia (Kochia scoparia) is an annual halophyte and drought resistant plant that can be irrigated with saline water and has the capability of being used as a valuable source of forage in ecosystems under drought and salinity stress. In order to evaluate germination characteristic of Kochia scoparia under different temperatures and water potentials, an experiment was conducted in 2009 at Physiology Lab of Ferdowsi University of Mashhad. Experiment was conducted in a completely randomized design with 4 replications. Treatments included 9 levels of water potential (-0.25,-0.5, -0.75.-1, -1.25,-1.5,-1.75 and -2 MP) and also the treatment not exposed to drought (control) and 8 temperature levels (5, 10, 15, 20, 25, 30, 35 and 40 0C). The results of variance analysis showed that different levels of temperature and water potential had a significant effect (P<0.01) on germination percentage, germination rate, mean germination time and germination index. Interaction effect between temperature and water potential on the mentioned parameters was also significant. The highest percentage of germination occurred at 20-250C and 4 primary levels of water potential with no significant differences between each other. Also, the highest germination rate occurred at 250C and in control treatment. With decrease of water potential, germination rate also decreased in all temperature treatments. In addition, decrease in water potential caused an increase in mean germination time. The lowest mean germination time was observed at 250C equivalent to 1.07 day. The highest germination index occurred at 250C and in control treatment. However, seeds of Kochia are able to germinate in a wide range of temperature and water potential.

Evaluation of forage production is an important issue in determining grazing capacity of rangelands. There is no doubt that all forage production in rangelands is not evenly accessible and different factors affect the accessibility of forage. In this research, factors affecting forage availability were studied. After a wide literature review, factors of distance from water supplies, density of shrubs, slope and land uses were identified as the main factors preventing forage accessibility. Forage production and shrub density were respectively measured using clip and weighing method in quadrates and distance method. Forage production measurements in representative area were extrapolated to the whole area using IRS satellite images. In this research, 18 vegetation indices were examined as forage production data (independent factor) were regressed against vegetation indices values (dependent factor) using SPSS. Map of forage production was created based on the best fit regression. Then, with adjusting all limiting factors, the map of accessible forage production was created based on the tables. The maps were illustrated and available forage was calculated after implementing adjustment of each factor. Statistical results showed significant differences (p≤0.05) between forage production with considering slope and shrub density and forage production based on all limiting factors of forage accessibility. While distance from water supplies and other land uses had no significant effect on forage production.

To investigate the response of extremely hard seeds of Prosopis species from Fabaceae family in germination phase and growth seedling under saline stress, a factorial experiment (ABC) was conducted on the basis of Completely Randomized Design (CRD) with three replications at Seed technology laboratory of Collage of Agriculture, Shahed University. Salicylic acid Hormone at three levels (0, 0.3 and 0.6 mM) and salinity stress (NaCl) at four levels (0, 5, 10 and 15ds.m-1) were applied to study seed germination of Prosopis under scarification treatments. The results of the study showed that salinity had no significant effects (P≤0.05) on germination rate which indicates high salt tolerance of the species. No seed germination was recorded for Pods and seeds cultivated under no scratch treatment. Proline, protein and carbohydrates content were highest in the treatment of 0.3 mM salicylic acid, 10 ds.m-1 salinity and broken pods containing scratched seeds. Generally speaking, the results showed that Prosopis seedling needs to get rid of physical barriers and inhibitory components within pod and seed coat in order to obtain high seed germination. Moreover, salinity tolerance of this plant was 15 ds.m-1 considered as one of the most important legume species which stabilizes nitrogen in desert and semi- desert regions for combat desertification.

Management activities like crescent intake and enclosure affect the soil surface indicators and rangeland functional attributes. To have a continuous and sustainable utilization of rangelands these changes must be recognized and managed. Indicators of soil surface characteristics and rangeland functional attributes assist researchers in judging the effects of their applied management activities. The aim of this study is to investigate the effects of management activities like crescent intake and enclosure on soil surface indicators and rangeland functional attributes. For this purpose, three regions including freed enclosure, enclosure and crescent intake were selected and the effect of any aforementioned activities on soil surface characteristics and rangeland functional attributes were investigated by using Landscape Functional Analysis (LFA) method. In this method, for determination of three functional attributes (stability, infiltration and nutrient cycle) 11 soil surface indicators were applied as follows: ground cover, litter cover, litter (degree of decomposition), cryptogam cover, soil surface resistance to distribution, eroded materials, erosion features, soil microtopograghy, soil surface nature, slake test and soil texture. Data analysis was performed with SPSS software, Kruskal-Wallis nonparametric test and a Duncan multiple range test. According to the results, the indicators and functional characteristics of the rangeland have been changed due to the management activities. As significant differences were found among all 11 soil surface indicators except erosion feature and cryptogam cover in three studied regions (P<0.05). Also significant differences were found among three rangeland functional attributes in three study areas. Our results indicate that crescent intake and enclosure could improve rangeland functional attributes.

To find an accurate and rapid method of estimating herbage standing crop, clipping and weighing, double sampling, and comparative yield methods were compared in two vegetation types of grasslands and one cushion shrubland in Sar-Aliabad summer rangelands of Golestan province. In representative stands of each vegetation type, eighty 1-m2 plots were clipped and weighed. In double sampling method, 16 plots were estimated and clipped. In comparative yield method, standard (reference) plots were used as the highest yield belonged to the reference plot 5 and the lowest yield belonged to the reference plot 1. A high correlation was found between estimated and clipped plot in double sampling method. There was also high correlation between reference plots and their weights, so estimation of double sampling and ranks of comparative yield method were corrected by using regression equations. There were no significant differences among 3 methods, but time consumption of double sampling was better than the other methods. So, because of extensive application of double sampling method in grasslands and shrublands and its high accuracy and precision this method of yield estimation is recommended for the study area.

Determination of forage quality of range plants is one of the fundamental factors for evaluating grazing capacity. There are spatial and temporal variations in forage quality of range species. In this study, samples from two halophyte species including Salsola arbuscula and Salsola richteri were collected at three phenological stages of vegetative growth, full flowering and seed dissemination with three replications at research station of Poshteh Abbas Sabzevar. The quality indices of acid detergent fiber (ADF), crude fiber (CF), crud protein (CP), metabolic energy (ME), dry matter digestibility (DMD) and soluble carbohydrate (WSC) were measured or estimated. Analysis of variance and Duncan's multiple range test were used for data analysis. The results indicated that forage quality of both species in vegetative growth was higher than the other stages. Forage quality indices and water soluble carbohydrates were significantly different at different phenological stages and between the species (P<0.05). Salsola richteri had a better forage quality than Salsola arbuscula in all phenological stages. Considering the result of this research, the second stage (flowering) was determined as the most suitable period for livestock grazing. Because at this time, forage quality and soluble carbohydrate of plant are desirable for grazing and grazing will cause less damage to plants.

Overgrazing can alter rangeland vegetation in different ways. In this study, we used diversity, species richness and plant functional groups as the alternative to assess the vegetation response to different grazing intensities. This was done under three grazing intensities (long-term exclosure as reference area, key area, and critical area) in rangelands of Mahoor Mamasani in Fars province. Vegetation sampling was carried out by random-systematic method and measuring the cover of plant species. The results showed that species diversity and richness significantly decreased with an increase in grazing intensity. Also, the cover percentage of Gramineae، Papilionaceae، Primulaceae، Umbelliferae and Valerianaceae significantly showed a negative response to grazing intensity while a positive response was found for Cruciferae، Labiatae، Plantaginaceae and Malvaceae. Moreover, some functional groups such as annuals, therophytes and Gramineae were significantly reduced from reference area to key area. The other finding of this study showed that decreaser plants significantly had less cover in critical area whereas increaser plants had greater cover in critical area. Species with storage of seeds in soil seed bank significantly had greater cover in aboveground vegetation in reference area than those species absent from soil seed bank. Due to the damage of some vegetation indices under overgrazing, it is recommended to make some changes in rangeland management and utilization in order to restore vegetation.