Morteza Abtahi; Abdollah Seif; Mohammad Khosroshahi
Volume 21, Issue 1 , June 2014, Pages 1-12
Abstract
Temperature and precipitation are basic constituent components of the climate of a region. For this reason, the assessment of present and future trends of these elements have been considered by different scientists such as natural resources or environmental experts. In this study, Namak lake basin was ...
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Temperature and precipitation are basic constituent components of the climate of a region. For this reason, the assessment of present and future trends of these elements have been considered by different scientists such as natural resources or environmental experts. In this study, Namak lake basin was divided in to six sub-basins and then monthly precipitation and temperature data were collected and reconstructed from 1956 to 2005. Average precipitation, maximum and minimum temperatures of sextuple sub-basins of the lake were calculated using Thiessen method in Arch Map software. In order to evaluate the precipitation trend, Standard Precipitation Index (SPI) was used. The trend of climatic factors (temperature and precipitation) was studied by linear regression and Mann-Kendall test. No significant trend was observed in standardized precipitation of the Namak Lake and in its sub-basins except in the sub-basin of Arak in which the trend of precipitation change was decreasing and significant. According to the study of monthly precipitation, strong droughts have been observed in sub-basins of Arak, Roodshoor and Karaj during the last 50 years. The trends of maximum and minimum temperature change were increasing and significant in most basins. Increasing the temperature of the Namak lake basin may be caused by several factors, including increasing greenhouse gases especially in big cities such as Tehran, Qom, Arak, Kashan, Hamadan, and Qazvin.
Ali Ehsani; Mamak Ahmadian; Saeed Rashvand; Mohammad Ali Dehghani Tafti; Mostafa Zare
Volume 21, Issue 1 , June 2014, Pages 13-23
Abstract
Study of the phenology of range key species is important to regulate and apply proper management for sustainable utilization of rangeland forage. In this study, the phenological stages of Artemisia aucheri were examined as a key species at three sites of different semi-steppe regions during 2007-2010. ...
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Study of the phenology of range key species is important to regulate and apply proper management for sustainable utilization of rangeland forage. In this study, the phenological stages of Artemisia aucheri were examined as a key species at three sites of different semi-steppe regions during 2007-2010. For this purpose, in each site, 10 individuals were selected and different phenological stages were recorded in 15-day and 7-day intervals for vegetative stage and reproductive stage, respectively. In addition, meteorological data including temperature and precipitation were recorded from the nearest synoptic station for each site. Results indicated that the occurrence of phenological phenomena of Artimisia aucheriwas more affected by temperature and precipitation indices of the growing season. According to the obtained results, the start and end of grazing were determined as early May to late October for Shirkooh (Yazd province), late May and early June to mid-July for Anjadan (Markazi province), and second half of May to mid September for Alamoot (Ghazvin province). Consequently, a complete understanding on the phenological stages of Ar. aucheri enables us to plan grazing management in order to determine the time of livestock entry into and exit from rangelands, optimal number of livestock for grazing and proper grazing systems.
Hossein Arzani; Zeinolabedin Hosseini; Khosro Mirakhorlou
Volume 21, Issue 1 , June 2014, Pages 24-31
Abstract
This study was aimed to assess the applicability of LANDSAT ETM+ satellite images for estimating vegetation production and cover. The images were digitized using topographic maps and geometrized in 1:25000 scales. Required processes such as spectral ratio measurement and vegetation indices were applied ...
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This study was aimed to assess the applicability of LANDSAT ETM+ satellite images for estimating vegetation production and cover. The images were digitized using topographic maps and geometrized in 1:25000 scales. Required processes such as spectral ratio measurement and vegetation indices were applied on the images. Collection was carried out for vegetation cover and production in various vegetation types in homogeneous units. Sampling points' locations were recorded with GPS. Sampling method was random-systematic in such a way that in each unit, a circle with 20 meters radius was considered. One and 9 sampling plots were placed on the centre and on the perimeter, respectively. The plot size was 1m * 1m. In each plot, vegetation percentage was estimated and the production was calculated using double sampling method. Then, DN values for each sampling unit (9 pixels for one unit) were elicited in respect to primary bands' images, vegetation indices and spectral ratios. Correlation and regression analyses between geo-information and satellite information (Digital numbers) were carried out. Results revealed that 7th and 5th Bands and IR1, MIRV2 and VNIR2 indices had a significant correlation with production and given parameter could be estimated through regression models. Likewise, RA, IR1 and TVI indices had a significant correlation with vegetation percentage and this parameter could be estimated through regression models.
Reza Bagheri; Seyed Mehdi Altaha Maki; Sedigheh Mohammadi
Volume 21, Issue 1 , June 2014, Pages 32-40
Abstract
Grazing management projects conducted by natural resources offices have been less evaluated in previous studies. This research was conducted in order to determine the effects of grazing management projects on vegetation and some soil physico-chemical properties in Dehsard region of Kerman province. Soil ...
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Grazing management projects conducted by natural resources offices have been less evaluated in previous studies. This research was conducted in order to determine the effects of grazing management projects on vegetation and some soil physico-chemical properties in Dehsard region of Kerman province. Soil and vegetation properties were sampled in early autumn in a completely randomized block design with three replications. Soil samples were taken from depths of 0-15 and 15-30 cm and soil properties including organic matter, total nitrogen, available phosphorus, available potassium, pH, texture, moisture, and electrical conductivity were measured. Fifty-meter length transects were established and species composition and canopy cover percentage were recorded by linear-contact method. Our results showed that grazing management project caused a double increase in the amount of organic matter and nitrogen in soil surface as compared to the adjacent rangelands. Increased shrub and bush species (3.8 and 5%, respectively) is important as the main source of forage. According to these changes over a period of six years in the project area, the effects of grazing management projects can be evaluated as positive.
Kourosh Behnamfar; Seyed Ataollah Siadat; Mohammad Hasan Salehe Shoshtari
Volume 21, Issue 1 , June 2014, Pages 41-50
Abstract
In order to study and design a mixed plantation of rangeland and forest species (silvopastoral system), four rangeland species and three shrub and tree species were planted with different row spacings on the sand dunes of Karkheh river, in Khuzestan province. The biological stabilization of sand ...
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In order to study and design a mixed plantation of rangeland and forest species (silvopastoral system), four rangeland species and three shrub and tree species were planted with different row spacings on the sand dunes of Karkheh river, in Khuzestan province. The biological stabilization of sand dunes and production of forage were the aims of this study. The selection of species was done according to their ability to improve the production of forage, firewood, and industrial wood as well as species diversity. The study was performed using split plot in a completely randomized design with three replications for four years. The main treatment included tree and shrub species (Eucalyptu camaldulensis 9616, Acacia victoriae ,Prosopis juliflora). Row spacings of 4*4, 5*5, 6*6, and rangeland species (Panicum antidotale,Cenchrus ciliaris ,Cymbopogon olivieri , Pennisetum divisum) were considered as the first and second sub-treatments, respectively.Vitality percentage of all species, forage yield of rangeland species, and height growth of shrub and tree species were measured. Data were analyzed by SAS software and mean comparisons were performed by Duncan's Multiple Range Test. According to the results, C. olivieri (90%) and C. ciliaris (60%) showed the highest and lowest vitality of rangeland species. Among tree and shrub species, E. camaldulensis (80%), P. juliflora (65%), and A. victoriae (50%), showed the highest vitality, respectively.In four-meter row spacings of E. camaldulensis, forage yield of all range species decreased. In terms of height growth, E. camaldulensis, with a height of around 3.5 m, was better as compared to the other two species. The highest average dry matter yield was recorded for P. divisum (1437 Kg ha-1), P. antidotale (1035 Kg ha-1), C. olivieri (380 Kg ha-1), and C. ciliaris (235 Kg ha-1), respectively. Therefore, the determination of appropriate row spacing for trees causes to increase of species diversity as well as continued and increasing forage production and utilization.
Azin Jafarian; Mohammad Jafari; علی طویلی
Volume 21, Issue 1 , June 2014, Pages 51-61
Abstract
Ecological effects of Haloxylon plantation on natural vegetation and soil properties were investigated in this study. For this purpose, three regions with 1 to 5-year-old, 5 to 10-year-old and over 20-year-old Haloxylon (Haloxylon persicum) and a control area for each region were determined. Vegetation ...
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Ecological effects of Haloxylon plantation on natural vegetation and soil properties were investigated in this study. For this purpose, three regions with 1 to 5-year-old, 5 to 10-year-old and over 20-year-old Haloxylon (Haloxylon persicum) and a control area for each region were determined. Vegetation sampling was conducted along a 300-meter transect to record crown cover percentage, density, production, litter, gravel ،bare soil ،species diversity and dominant species. In addition, soil sampling was performed at depths of 0-30 and 30-90 cm to measure soil properties including EC, pH, percentage of organic carbon, soluble calcium, magnesium and sodium, and silt, clay and gravel percentage. The study was performed through random-systematic sampling. Data were analyzed using independent t-test in SPSS software. Results indicated that Haloxylon plantation led to increase in percentage of crown cover, litter, and standing crop production. It also caused improvement in species composition, condition and trend as compared to the control area. Plantation of Haloxylon with different ages affected and increased soil electrical conductivity.
Hamidreza Fallahi; Parviz Rezvani Moghaddam; Mehdi Nassiri Mahallati; Mohammad Ali Behdani
Volume 21, Issue 1 , June 2014, Pages 62-74
Abstract
In this study, the effects of reconstruction and conservation were investigated on plant diversity of the region of the international Carbon Sequestration Project in Hussein-Abad, South Khorasan province. In the study area, four vegetation types including Haloxylon persicum, Atriplex conescens, Haloxylon ...
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In this study, the effects of reconstruction and conservation were investigated on plant diversity of the region of the international Carbon Sequestration Project in Hussein-Abad, South Khorasan province. In the study area, four vegetation types including Haloxylon persicum, Atriplex conescens, Haloxylon persicum + Atriplex conescens and Zygophyllum eurypterum were planted in 2004. Six years after that, the plant diversity indices of four replanted vegetation types along with control vegetation type (no replanting and conservation programs) was studied in two different dates (April and May) in 2011. For this purpose, 51 quadrates (2 × 2 m) were used in each vegetation type. Results showed that the maximum plant diversity and vegetation coverage were observed in Haloxylon persicum + Atriplex conescens (30 species and 22.5%, respectively) vegetation types, and the minimum values of these indices were recorded in control (20 species and 5.5%, respectively) vegetation type. The highest and the lowest values of plant density were obtained in Atriplex conescens (539,000 plant. ha-1) and control (179000 plant. ha-1) vegetation types, respectively. The Margalef’s richness index was higher in all protected vegetation types, while uniformity index and Shannon diversity index were higher in the control vegetation type. The frequency of 65% of plant species was less than 20% and about 45% of the plant species belonged to therophytes. Overall, the experimental results showed that desert ecosystems could play an important role to improve global biodiversity if proper management programs are employed.
Aezam Khosravi Mashizi; Najmeh Faryabi; Nematollah Maddadi Zadeh
Volume 21, Issue 1 , June 2014, Pages 75-82
Abstract
To study the role of shrubs refuge for annual plant inside and outside exclosure, in Goghar, Bafte, quadrates of 20cm×20 cm were plotted beneath 20 species of Artemisia aucheri, Astragalus gosipinus and 20 open patches, then the name and number of annual species were recorded in quadrates. Species ...
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To study the role of shrubs refuge for annual plant inside and outside exclosure, in Goghar, Bafte, quadrates of 20cm×20 cm were plotted beneath 20 species of Artemisia aucheri, Astragalus gosipinus and 20 open patches, then the name and number of annual species were recorded in quadrates. Species responses to grazing and shrubs were analyzed by two-way ANOVA and Post-Hoccomparisons. Results showed that shrubs acted as biotic refuges by protecting 7 species of 22 annual species against direct grazing. Although these seven species are palatable plants but Artemisia aucheri and Astragalus gosipinus that are less palatable in growing season of annual plants can have refuge role for palatable annual plants in grazed plant communities. Some annual species that were rather abundant under the shrubs were rarely found in the open patches in both the grazed and ungrazed quadrates. These species were most probably facilitated by the shrubs. Consequently, shrubs have important implications for diversity, conservation, and management in grazed ecosystems because of their facilities and roles as refuge.
Zahra Soleimannejad; Ahmad Abdolzadeh; Hamid Reza Sadeghi Pour
Volume 21, Issue 1 , June 2014, Pages 83-94
Abstract
Puccinellia distans is a perennial, salt tolerant forage species that belongs to Poaceae family. The main objective of the present study was to evaluate the effect of different levels of salinity ongrowth, antioxidant enzymes activity and mineral accumulationin Puccinellia distans. The experiment was ...
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Puccinellia distans is a perennial, salt tolerant forage species that belongs to Poaceae family. The main objective of the present study was to evaluate the effect of different levels of salinity ongrowth, antioxidant enzymes activity and mineral accumulationin Puccinellia distans. The experiment was conducted based on a completely randomized design with five replications in green house. Salinity levels included 0, 100 and 200 mM NaCl. Plants were harvested before reproductive stage. The results indicated that salinity imposed significant reduction in growth of plants including shoot and total length, fresh and dry weight, leaf number and relative water content. Concentration of Na+ decreased and concentration of K+ and K+/Na+ ratio increased due to salinity in both shoots and roots. The activity of catalase and polyphenol oxidase decreased in shoots of plants treated with 200 mM NaCl compared to control, however, the activity of catalase, cell wall and soluble peroxidase, and polyphenol oxidase in roots and cell wall peroxidase in shoots of plants indicated significant increase due to the same salt treatment. Salt treatments led to increase of chlorophyll a, total chlorophyll and carotenoids contents and the amount of hydrogen peroxide. However, no significant change was observed in the amount of lipid peroxidation in roots and shoots. The results indicated that in spite of growth retardation and Na+ accumulation, salt treatments did not induce oxidative stress in Puccienellia distans. The reduction of K+ concentration, K+/Na+ ratio and relative water content may cause decrease of plant growth.
Mohammad Jafari; Hossein Azarnivand; Mahshid Souri; Seyedeh Khadijeh Mahdavi
Volume 21, Issue 1 , June 2014, Pages 95-108
Abstract
Water deficiency and low soil moisture, are considered as limiting factors in rehabilitation and improvement of semi-arid rangelands. Considering the problem of water deficiency and low soil moisture in pastures discussed, rainfall storage projects can be one of suitable strategies to compensate for ...
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Water deficiency and low soil moisture, are considered as limiting factors in rehabilitation and improvement of semi-arid rangelands. Considering the problem of water deficiency and low soil moisture in pastures discussed, rainfall storage projects can be one of suitable strategies to compensate for water shortages in such areas. On the other hand, considering several criteria that must be considered in this selection, makes it difficult to choose the appropriate locations to execute projects such as pitting and furrowing. These factors include technical and social-economical criteria. Meykhoran region in Kermanshah Province was considered in this research. In this study, in order to locate suitable areas for pitting and furrowing projects, spatial decision support system were used in three stages. The first stage involves determining hierarchical levels consisting of object, criteria, sub-criteria, and factors. During the second stage, the standardization of criteria based on fuzzy logic, weighting criteria and sub-criteria based on analytical hierarchy process, and paired comparisons of criteria and sub-criteria, with preference values of one to nine and an inconsistency rate of less than one-tenth, were done in ARC-GIS software by using AHP subprogram. In the final step, after integration of these layers, the final maps of optimal sites for pitting and furrowing were prepared. Using this template to locate other natural resources projects will help to optimize use of spatial data, save time and costs.
Elham Fakhimi Abarghouie; Seyed Akbar Javadi
Volume 21, Issue 1 , June 2014, Pages 109-118
Abstract
From the perspective of rangeland ecology, awareness of the effects of livestock grazing on the changes of structure, plant vegetation and soil characteristics is essential. The aim of this study was to determine the effect of different grazing intensities including heavy (0-200 m distance from water ...
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From the perspective of rangeland ecology, awareness of the effects of livestock grazing on the changes of structure, plant vegetation and soil characteristics is essential. The aim of this study was to determine the effect of different grazing intensities including heavy (0-200 m distance from water point), moderate grazing (200- 800 m) and light grazing (800-1200 m) intensities on vegetation indices and soil characteristics in Nodushan region, Yazd province of Iran. For this purpose, plant vegetation cover and composition were recorded under three grazing intensities. Soil was sampled from depths of 0-30 cm. Data were analyzed by one way ANOVA, t-testandordination method (CCA) to assess the vegetation response in different grazing intensities. Results showed that plant species such as Astragalus achrochlarus, Salsola arbusculata and Tragopogon sp.were found in light grazing area.Allysum minus, Artemisia sieberi, Poa sinacia, Iris songarica, Lactuca glacifolia and Stipa barbata were identified in moderate grazing area. Eryngium sp., Cousinia desertii, Bromus tectorum and Peganum harmala were the major species in heavy grazing area.Soil properties including N, P, K, OC, EC and pH were measured. According to the results, nitrogen and soil organic matter were decreased by increasing grazing intensities but P, K, EC and pH were increased. Since grazing pressure causes damage to vegetation and some soil properties, a moderate grazing is recommended for sustainable utilization of rangelands.
Razieh Mohammadi; Kamaladdin Naseri; Gholamali Heshmati
Volume 21, Issue 1 , June 2014, Pages 119-127
Abstract
This study was conducted to investigate the effects of Haloxylon aphyllum plantation on natural plant communities and soil properties of Abbas-Abad area in Khorasan Razavi Province. For this purpose, Haloxylon plantation and control areas were selected to compare with each other. In each area, fifty- ...
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This study was conducted to investigate the effects of Haloxylon aphyllum plantation on natural plant communities and soil properties of Abbas-Abad area in Khorasan Razavi Province. For this purpose, Haloxylon plantation and control areas were selected to compare with each other. In each area, fifty- meter transects were located by random-systematic method. Measurements were done by point sampling method. Eighteen soil samples were collected from Haloxylon plantation and control areas to determine EC and pH values in the laboratory. Data were analyzed by t-test. According to the results, although higher species diversity was significant in Haloxylon plantation area (P<0/05), Haloxylon caused the replacement of non-native communities, so that only 64.28% of species composition in Haloxylon plantation area was similar to the control area. On the other hand, higher soil pH and EC in Haloxylon plantation area was significant (P<0/01) and probably in the long term, Haloxylon causes the salinity and alkalinity of the soil surface.
Nematollah Madadi Zadeh; Hossein Arzani; Ghavaloddin ahedi; Najmeh Faryabi
Volume 21, Issue 1 , June 2014, Pages 128-138
Abstract
In the current study, the effects of exclosure were examined on rangeland vegetation at two study sites including, reference site (inside the exlosure) and critical site (outside the exclosure). Research was conducted by the systematic-random method and 160 2*1.5 m plots were established. Inside each ...
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In the current study, the effects of exclosure were examined on rangeland vegetation at two study sites including, reference site (inside the exlosure) and critical site (outside the exclosure). Research was conducted by the systematic-random method and 160 2*1.5 m plots were established. Inside each plot, the percentage of canopy cover, litter, gravel and bare soil as well as density of class I, II, and III species were recorded. Dry matter yield was also calculated. Four-factor method and trend balance method were applied to determine the range condition and range trend, respectively. According to the obtained results, due to the exclosure, litter, yield, canopy cover percentage and class I species composition increased up to 24.72%, 37.42%, 23.6%, and 80.6%, respectively. On the other hand, the percentage of bare soil, gravel, and class III species composition decreased to 34.29%, 17.16%, and 26.96%, respectively. Mean differences in all parameters inside and outside the exclosure were significant at both study sites. Our results also indicated that exclosure led to the improvement of range condition and range trend.
Mostafa Jafari
Volume 21, Issue 1 , June 2014, Pages 139-153
Abstract
Iran faced with climate and environmental changes in past years and it is projected that some climatic changes will occur in the future. Net Primary Production (NPP) is an important index to evaluate production in natural ecosystems including forest, rangeland and desert. Climate change impact will cause ...
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Iran faced with climate and environmental changes in past years and it is projected that some climatic changes will occur in the future. Net Primary Production (NPP) is an important index to evaluate production in natural ecosystems including forest, rangeland and desert. Climate change impact will cause changes in biomass production in natural ecosystems. In this research, the vulnerability of NPP in Iranian forest, rangeland and desert ecosystem has been considered. Results of this consideration presented here in six selected climatic zones in Gilan, Mazandaran, East Azerbyjan, Kermanshah, Khorasan and Systan and Baluchestan provinces. According to the result outcomes, total NPP of forest, rangeland and desert ecosystem in Gilan, East Azerbyjan, and Khorasan provinces, under temperature and precipitation changes, has been increased in the year ended 2039. While, the amount of NPP in Mazandaran, Kermanshah, and Systan and Baluchestan provinces would have been decreased. These changes in Khorasan provinces (including North, South and Razavi) will show highest increase, indicating suitable increase of precipitation and temperature in the region. Quantitative changes in NPP depend on total biomass and changes of precipitation and temperature. As an example, these changes in forest ecosystems of Gilan, and Khorasan provinces, will increase and in Mazandaran, and Kermanshah provinces, will decrease. Also, these changes in range ecosystems of East Azerbyjan, and Khorasan provinces, will increase and in Kermanshah, and Systan and Baluchestan provinces, will decrease. While, changes in desert ecosystems of Khorasan provinces mainly will increase and in Systan and Baluchestan provinces, will decrease.
Masoumeh Rezaie Mashaie; Ghorbanali Nematzadeh; Hossein Askari; Ehsan Shokri
Volume 21, Issue 1 , June 2014, Pages 154-164
Abstract
Aeluropus littoralis, a monocot halophyte, plays an effective role in the conservation of water and soil resources and the production of forage for livestock in saline lands. In the current study, physiological characteristics of Aeluropus littoralis was investigated in response to different salinity ...
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Aeluropus littoralis, a monocot halophyte, plays an effective role in the conservation of water and soil resources and the production of forage for livestock in saline lands. In the current study, physiological characteristics of Aeluropus littoralis was investigated in response to different salinity levels. After disinfection, the seeds of Aeluropus littoralis were cultured in acid-washed sand in a growth chamber under controlled condition, temperature of 25/16 °C and photoperiod of 14/10 h for day/night. After 45 days of start culture, salinity treatments (0,100,200,300,400mM NaCl) were applied. The experimental design was completely randomized design with five treatments and three replications. After 14 days of last salinity treatment, plant materials were harvested. Results showed that the highest amount of shoot dry weight and ash content was observed in 200 mM NaCl. According to the results, potassium content of the shoot unlike sodium decreased with increasing salinity, while secreted sodium and potassium from plant aerial parts increased. Root carbohydrate content and the ratio of chlorophyll a to b increased in response to salinity. The concentration of starch and total soluble sugars of shoot demonstrated no significant relationship with the ratio of chlorophyll a/b at the highest salinity level. Our results suggested that the management of detrimental ions along with the regulation of plant assimilations effectively involved in the performance of Aeluropus littoralis to avoid the inhibitory effect of saline condition.
Hamidreza Mirdavoodi
Volume 21, Issue 1 , June 2014, Pages 165-175
Abstract
In this study, the adaptation of six species was investigated in a split plot design for autumn and spring sowings with three replications. The study was conducted in Khoshkrood Aquifer, located in the northwestern of Saveh for three years (2007-2010). The study area has a mean annual rainfall of 234.8 ...
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In this study, the adaptation of six species was investigated in a split plot design for autumn and spring sowings with three replications. The study was conducted in Khoshkrood Aquifer, located in the northwestern of Saveh for three years (2007-2010). The study area has a mean annual rainfall of 234.8 mm, loamy-textured soil, low soil salinity, a soil alkalinity of 8.1 with an appropriate infiltration and high drainage. The study range species were cultivated in pots with a distance of 2.5 m from each other, in late December and early March. According to the results, the highest and lowest viability were recorded for Kochia prostrate and Atriplex canescens (76.9 and 61.6%, respectively) and Halimion verrucifera (14.4%). In addition, the study species showed different responses during the years of experiment with a significant difference in the years of study. Results showed that the highest and lowest vegetation cover and vitality were recorded for K. prostrate and H. verrucifera, respectively with a significant difference at 1% level.The results of mean comparisons of vegetation and vitality were significant in different years at 1% level. However, the effect of sowing date was not significant on viability, vegetation cover and vitality, although the values of these factors were more in autumn sowing as compared to spring sowing. Overall, K. prostrate, a native species to the region, showed superiority in terms of establishment, vitality and vegetation cover as compared to other study species; therefore, the cultivation of this species is recommended for this region.
Fatemeh Hadian; Hossein Bashari; Reza Jafari; Saeed Soltani
Volume 21, Issue 1 , June 2014, Pages 176-187
Abstract
Selecting the appropriate satellite images is highly important to achieve acceptable precision and accuracy in rangeland assessment programs. This study aimed to evaluate Landsat5 (TM sensor) and IRS-P6 (AWiFS sensor) satellite images in three rangeland vegetation types in Semirom region, Isfahan. Ten ...
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Selecting the appropriate satellite images is highly important to achieve acceptable precision and accuracy in rangeland assessment programs. This study aimed to evaluate Landsat5 (TM sensor) and IRS-P6 (AWiFS sensor) satellite images in three rangeland vegetation types in Semirom region, Isfahan. Ten vegetation indices of different groups including slope-based, distance-based and plant-water sensitive indices were calculated and evaluated for all vegetation types. The percentage of canopy cover, litter, rock, gravel, stone and bare ground were determined using step-point method in radial direction (6000 points per rangeland type). Then, the correlations between the measured field components and spectral indices were compared. According to the results, vegetation indices extracted from TM sensor data had higher correlation with field vegetation cover due to its high spatial resolution. Factors such as characteristics of study area, range condition and vegetation types had also vital role in these correlations. The indices were tested against vegetation cover percentage in all vegetation types including Bromus tomentellus, Astragalus spp-Daphne mucronata- and Astragalus spp-Scariola orientalis. The highest determination coefficient was found between live vegetation cover and SSI index (r2=0.85) in Astragalus spp-Daphne mucronata vegetation type. Overall, the results showed that there was an inverse relationship between vegetation cover indices and rangeland condition. TM vegetation indices had minimum of 24 percent of determination coefficient in very poor range condition in comparison with other studied rangeland conditions. Therefore, the performance of a vegetation index highly depends on rangeland condition, vegetation types and also spatial resolution of remote sensing data.