Moselm Rostampour
Abstract
This study compared of univariate outlier detection methods among vegetation data in a study of the effect of grazing intensity in the rangelands of arid regions. For this purpose, after measuring the vegetation cover in the rangeland and before the statistical analysis, the presence of outlier data ...
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This study compared of univariate outlier detection methods among vegetation data in a study of the effect of grazing intensity in the rangelands of arid regions. For this purpose, after measuring the vegetation cover in the rangeland and before the statistical analysis, the presence of outlier data was examined as the assumption of parametric comparison tests. In this study, eight methods including the boxplot and IQR (Tukey method), standard deviation of the mean (three-sigma rule), median absolute deviation (Hampel method), trimmed mean, 1st percentile and 99th percentile, The Chi Square test (χ²), the Grubbs Test (ESD) and the Rosner test (generalized ESD) were used. The results showed that the vegetation cover of rangelands with light and moderate grazing intensity was not normally distributed (Shapiro-Wilk test: p≤0.05). Even deletion of outliers did not lead to a normal distribution, but it resulted in the homogeneity of variances (Levene's test: p≥0.05). The modified Z-score and the Grubbs and Rosner tests (p≥0.05) did not identify outliers from the vegetation cover data. Among the methods evaluated, the boxplot and MAD method, which are not dependent on the mean, are more suitable for the vegetation cover. Therefore, before performing any comparison test, a combination of visual and statistical methods is recommended to evaluate the presence of outliers.
Ali Asghar Naghipour; Maedeh Sharifi; Ataollah Ebrahimi; Elham Ghesareh Ardestani; Sina Nabizadeh
Abstract
Fire is one of the important ecological factors that affect the dynamics of rangeland vegetation. In recent decades, the incidence of wildfires in semi-steppe rangelands has increased significantly, challenging the adaptive capacity of plants for post-fire regeneration. In the present study, the germination ...
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Fire is one of the important ecological factors that affect the dynamics of rangeland vegetation. In recent decades, the incidence of wildfires in semi-steppe rangelands has increased significantly, challenging the adaptive capacity of plants for post-fire regeneration. In the present study, the germination response of eight annual and perennial herbaceous species of semi-steppe rangelands of Chaharmahal va Bakhtiari province to fire products treatments including heat (60, 80 and 100° C), smoke, ash, and the combined effect of heat and smoke treatments were investigated. Also, percentage cover change of studied species, one year after the fire were measured in the field. The results showed that the germination of seeds of eight studied plant species showed a significant positive or negative reaction to at least one of the fire product treatments. Combined treatment of smoke and 60° C caused a significant increase in the mean germination percentage of Heteranthelium piliferum. This treatment also significantly reduced the mean germination time of Cousinia cylindracea. Ash treatment also increased the mean germination percentage of Alyssum linifolium and Stachys lavandulifolia. Vegetation sampling results also showed that among the eight species studied, H. piliferum and Taeniatherum crinitum were fire adapted and six species were tolerant. The results of this study can be used as a potential factor to understand the dynamics of vegetation and restoration of degraded rangelands.
moslem yazdani; reza erfanzadeh; Asghar Mosleh Arani
Abstract
Study of the effect of woody plant species on the production, diversity and richness of substratum herbaceous species, especially in the arid and semiarid regions, is essential for the proper management of these ecosystems. Therefore, the rangelands of Chenarnaz region in Khatam city in Yazd province ...
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Study of the effect of woody plant species on the production, diversity and richness of substratum herbaceous species, especially in the arid and semiarid regions, is essential for the proper management of these ecosystems. Therefore, the rangelands of Chenarnaz region in Khatam city in Yazd province were selected and then, using 0.5m×0.5m quadrats, vegetation sampling was performed under the selected 15 sites from Daphne mezerum, Amygdalus scoparia and Ebenus stellate (growing in equal topographical conditions) canopies, and outside of the canopies (as control). In each quadrat, the cover percentage of each plant species was visually estimated and the productions were measured by clipping and weighing method. The species diversity and richness indices were calculated using Past software through introducing the plant covers into the software. The results showed that the most values of Shannon-Weaner and Simpson diversity indices were found under A. scoparia (2.07 and 0.80, respectively) and the lowest values were found under E. stellata (1.010 and 055, respectively). In addition, the highest values of Menhinik and Margalef richness indices were found under A. scoparia (4.90 and 3.43, respectively) and D. mezerum (4.25 and 3.12, respectively), while the highest production was found under E. stellata (64.76 g/m2). The results of this study showed that different woody species had the desired but different effects on the herbaceous species, in such, A. scoparia and D. mezerum had significant positive effects on species diversity and E. stellata increased significantly species production; therefore, conservation of all woody species is emphasized in the region.
mahshid souri; mina bayat; Hossein Arzani; Morteza khodagholi
Abstract
Climatic factors are the most important factors affecting vegetation growth and production. The impact of each of these factors in each region varies depending on the vegetation type. The effect of climatic factors (rainfall and temperature) on the production of grazed plant species at 6 steppe sites ...
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Climatic factors are the most important factors affecting vegetation growth and production. The impact of each of these factors in each region varies depending on the vegetation type. The effect of climatic factors (rainfall and temperature) on the production of grazed plant species at 6 steppe sites in Fars province over a ten year period (1998 to 2007) was investigated. 60 plots of 2 square meters along 4 transects of four hundred meters were used to measure cover and production was measured by cutting and weighing method in 15 plots along transects. Then, using regression relationship between canopy cover (percent) and production (kg ha-1), the residual plot yield was calculated for that year. Important climatic indices analyzed in this study are: annual rainfall, growing season rainfall (March to June), plus and earlier rainfall, annual temperature, July temperature, August, maximum and minimum temperatures. The results showed that the average canopy cover was 6.3% and the average yield was 128.5 kg / ha and among the different vegetative forms of shrubs had the highest percentage of cover and production and wheat had the lowest cover and production percentage. Among the important climatic indices, annual rainfall and August temperature at all sites and the growing season rainfall at all sites except for the desired site were the most effective indicators on forage production and showed a positive and significant correlation with forage production.
Abdolhosain Mohammadi; Reza Ghazavi; rohollah Mirzaei; Hamidreza Naseri
Abstract
Rainfall is one of the most important factors affecting vegetation cover. Fluctuation and year-to-year variation of rainfall always affect vegetation cover patterns. The main aim of this study was to investigate and modeling the effects of rainfall changes on the variation of the vegetation cover in ...
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Rainfall is one of the most important factors affecting vegetation cover. Fluctuation and year-to-year variation of rainfall always affect vegetation cover patterns. The main aim of this study was to investigate and modeling the effects of rainfall changes on the variation of the vegetation cover in the Meyghan basin in Arak province using MODIS satellite images. NDVI, DVI, RVI and EVI indices were used to manifest vegetation covert variations linear and nonlinear relationship between vegetation cover changes and rainfall investigated simultaneously (May), with one and two month delay (April and March) ) during the statistical period of 2000-2017. The rainfall trend analysis was done using non-parametric Mann-Kendall test. According to the results, the minimum rainfall during the 18-year period was increased. Between vegetation indices, NDVI index showed the maximum and the average incremental trend. Between precipitation and vegetation, third-order non-linear relationship was stronger than linear, quadratic, power, logarithmic and exponential. The maximum correlation between DVI index and rainfall was obtained for synchronous times, while, the maximum correlation was observed between NDVI index and precipitation. The study with two month delay showed that the maximum correlation (0.52) was between the RVI index and precipitation. Vegetation modeling using simultaneous rainfall and delay of up to two months showed that the indices of DVI, RVI and EVI provided the best regression relationship at the same time, while the NDVI index had the best regression relationship with rainfall of two months ago.
maryam etehadi abari; a a; a a; meghdad jur gholami
Abstract
Land cover is also important factor for protecting the soil against erosion. A fully forested watershed experiences relatively little surface erosion, but timber harvest alters the canopy cover, exposing the soil to water and wind. Forests provide the maximum amount of soil protection. Reduction of vegetative ...
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Land cover is also important factor for protecting the soil against erosion. A fully forested watershed experiences relatively little surface erosion, but timber harvest alters the canopy cover, exposing the soil to water and wind. Forests provide the maximum amount of soil protection. Reduction of vegetative cover by forest harvesting generally increases the average surface runoff volume and sediment While, the hydrologic response of forest harvesting has been rarely considered. Towards this attempt, the present study has been conducted to investigate the effect of vegetation cover on hydrological components in plot scale (2m*1m) with four replicates in tow slope scale (0-20%, 20-40%) in Kheyrud Forest of Iran during December 2014 until December 2015. The rain depth was measured by using a rain gauge installed in the study area. The runoff volume and sediment yield were also measured through field data collection and lab analyses by weighting and decantation methods. The results of the study showed significant effects of vegetation cover (P ≤0.01) on runoff volume and sediment yield. Natural forest without harvesting, forest with selective harvesting treatments exhibited the lowest amounts of runoff and sediments, with averages of 372.31, 878.96 cc, and 0.08, 0.17 gr m-2 respectively, in comparison to other treatments. Linear regression among mentioned parameters (precipitation, runoff, and sediment) were determined. The results show that there were significant correlation and linear regression among precipitation, runoff and sediment.
zohreh asar; masoud masoudi
Abstract
Desertification refers to land degradation in arid, semi-arid, and dry sub-humid region. It is a global environmental problem with political and socio-economic consequences. Land degradation occurs as a result of impoverished vegetation cover that may lead to a progressive and irreversible reduction ...
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Desertification refers to land degradation in arid, semi-arid, and dry sub-humid region. It is a global environmental problem with political and socio-economic consequences. Land degradation occurs as a result of impoverished vegetation cover that may lead to a progressive and irreversible reduction of the biological or economic productivity. Overgrazing may cause degradation of soil and vegetation. Degradation of vegetation and soil in dry lands, sometimes called desertification, is thought to be a serious threat to the sustainability of human habitation. Therefore, the intensity of grazing can serve as an index of environmental pressure. The Miandehi region, located in the Northeast Iran, has been selected as a test area to assess livestock pressure. Present paper assessed the pressure of livestock within the studied area using GIS. FAO-UNEP model (1984) proposes the use of a ratio of potential carrying capacity to present livestock density as an estimate of pressure of livestock. This method has been adopted with some modifications for the present study. Therefore, maps of the hazard of pressure of livestock were prepared after overlying and calculating different parameters in GIS. According to the final map of pressure of livestock in Miandehi region, areas of no hazard, slight hazard, severe hazard and very severe hazard comprised respectively 21.3, 5.6, 9.8 and 63.3 % of the study area. Results showed that areas under very severe hazard dominate Miandehi (63.3 % of total land).
Ataollah Ebrahimi
Abstract
Canopy cover and forage production have always been two important indicators in rangeland assessment, which sometimes are applied as surrogates of each other. These two indicators are widely used in rangeland studies and have a vital role in evaluation of rangeland structure and functions. Occasionally, ...
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Canopy cover and forage production have always been two important indicators in rangeland assessment, which sometimes are applied as surrogates of each other. These two indicators are widely used in rangeland studies and have a vital role in evaluation of rangeland structure and functions. Occasionally, different sampling groups (estimators) evaluate forage production and canopy cover of different spaces and times. This research was aimed at investigation of different sampling groups and life-forms' effects on relationship between canopy cover and forage yield estimation. To do so, the impact of three sampling groups and five life forms (Fixed factors) on estimation of relationship between canopy cover (covariate) and forage yield (dependent variable) in a full factorial model in rangeland of Chahrtagh of Naghan, Chahrmhal-va-Bakhtiari Province, was estimated. Results shows that predictor variable of canopy cover is a god surrogate for forage production (P≤0.05) of different life-forms, but different sampling groups significantly (P≤0.05) effects on relationship between canopy cover and forage production estimation. Nevertheless, different life-forms do not significantly (P≤0.05) influence estimation of canopy cover and forage production relationship. By the way, interaction between sampling group and life forms considerably (P≤0.05) affects the relation. Therefore, we conclude that, although, the canopy cover is a good predictor of forage production, nonetheless, different sampling groups should not be engaged in sampling and monitoring vegetation cover and forage production estimation, specifically, if estimation of different life-forms' production is intended.
fatemeh naghizadeh; mohammad jafari; hosein azarnivand; Mohammad Ali Zare Chahouki
Abstract
In this study, the role of soil properties in making difference between plant communitieswas examined. First, four plant types were identified, including Pteropyrumaucheri-Salsolarigida، Astragalus gossypinus - Acanthophyllum herateens، Amygdalus scoparia – Achilla millefolium and Ephedra intermedia ...
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In this study, the role of soil properties in making difference between plant communitieswas examined. First, four plant types were identified, including Pteropyrumaucheri-Salsolarigida، Astragalus gossypinus - Acanthophyllum herateens، Amygdalus scoparia – Achilla millefolium and Ephedra intermedia – Erigon capestra, through randomized systematic sampling and field survey in representative area of each type. In each plant type, three 500-meter transects were selected and in each transect, ten plots were placed along each transect. Characteristics of vegetation such as type and percentage of cover, gravel percentage, litter percentage and bare soil percentage were determined within each plot. In addition, in order to study the soil properties, at the beginning and at the end of each transect, a profile was dug and soil samples were taken from the depths of 0-20, 20-80 cm. Soil physical and chemical properties (texture, pH, electrical conductivity, organic matter percentage, gypsum percentage, lime percentage, salts such as sodium, potassium, calcium and magnesium, sodium absorption ratio, sodium exchange percentage) were determined in soil laboratory. Then, the role of soil properties in making difference between plant communitieswas determined by using ANOVA statistical analysis, and the key factors making this difference were introduced as sand percentage, organic matter percentage, and electrical conductivity.
Shafagh Rastgar; Hossein Barani; Ali Darijani; Vahedberdi Sheikh; Jamshid Ghorbani; Mohammad Ghorbani
Abstract
Vegetation cover as the main factor affecting the water erosion plays an important role in preventingsoil loss. To this end, for better understanding the impact of vegetation cover on soil erosion andsediment yield over the major existing geological formations in the summer rangelands of Balade inthe ...
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Vegetation cover as the main factor affecting the water erosion plays an important role in preventingsoil loss. To this end, for better understanding the impact of vegetation cover on soil erosion andsediment yield over the major existing geological formations in the summer rangelands of Balade inthe Mazandaran province, rainfall simulation studies have been carried out using a portable rainfallsimulator. Among many geological formations across the study area, the three major lithological unitsof mica sandstone, clay and shale sandstone with coal seams of “SHEMSHAK”, structures of tuffshale and dark gray to green shale with volcanic rocks of “KARAJ” and limestone of “LAR” havebeen selected as lowly, moderately and highly resisting formations to degradation. For eachcombination of geological formation and vegetation cover (low, moderate, and high density) threesampling plots of 1x1m have been selected and rainfall simulation has been conducted over them. Foreach plot, the surface characteristics including the vegetation cover, runoff and sediment yield and soiltexture were measured. The measured data were statistically analyzed. Results showed that“SHEMSHAK”, “KARAJ” and “LAR” formations were respectively ranked from highest to lowestwith respect to the volume and weight of sediment yield. Also, there was a strong inverse relationshipbetween vegetation cover percentage and volume of runoff and sediment for all investigatedgeological formations specially in poor vegetation situation that indicate interaction effects betweenvegetation cover and type of geological formations.
Fatemeh Hadian; Reza Jafari; Hossein Bashari; Saeed Soltani
Abstract
Because soil moisture condition affects vegetation changes hence, monitoring of drought and vegetation changes are among valuable management tools in these ecosystems. Nowadays, satellite images are used as a low-cost and fast method for vegetation study in different scales. Vegetation change is assessed ...
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Because soil moisture condition affects vegetation changes hence, monitoring of drought and vegetation changes are among valuable management tools in these ecosystems. Nowadays, satellite images are used as a low-cost and fast method for vegetation study in different scales. Vegetation change is assessed using vegetation spectral characteristics. This study aimed to analyze and monitor the vegetation cover changes in 4 rangelands and one forest type site in south of Isfahan and southeastern of Chaharmahal and Bakhtiary province during 1997-2009 ّField sampling were used for measuring the percentage of canopy cover in all vegetation types using step-point method in radial direction (6000 points per vegetation type). Regression analysis technique was used to ensure if vegetation cover can be measured properly using a Landsat images from 2009. Then NDVI indices were derived from 12 Landsat images between 1997 to 2009 (all images were taken from 22th of May to 5th of Jun each year) to monitor vegetation changes. According to results, there was significant correlation between NDVI indices and canopy cover in all vegetation types. Evaluating the canopy cover changes indicated that the precipitation had various effects on different vegetation types based on their plant form and ecological condition. T
Alibeman Mirjalili; Mohammad Musaei Sanjeraei; Shahabodin Zarezadeh Mehrizi
Abstract
A better understanding of rangeland vegetation cover and its variation in different years basedon wetness and droughtiness fluctuations is a great importance. Economical priority setting ofrangelands is based on variations in rainfall and drought patterns, because it yields to bettercharacterization ...
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A better understanding of rangeland vegetation cover and its variation in different years basedon wetness and droughtiness fluctuations is a great importance. Economical priority setting ofrangelands is based on variations in rainfall and drought patterns, because it yields to bettercharacterization of vegetative cover. Yet a comprehensive and continuous monitoring ofvegetative cover of rangelands has not been established. To study the influence of droughtinessand wetness on vegetation cover and production forage, 11 sampling areas and 3 referenceareas were selected in Herat. Three 100-m transects were located 25-m apart within eachsampling area. Production and cover were estimated within 10 located 2- plots along eachtransect. Data were analyzed using Duncan›s test Design a completely random with a factorialGLM procedure at 99% and 95% confidence levels. Results showed that the vegetation coverand production in wetness were significantly different from those in droughtiness (P<0.01).The vegetation production and cover increased by 36.3% and 34% respectively in the wetnesscompared to the droughtiness. The influence on production and cover was positive and efficientin the wetness with the average rainfall higher than the 30-yr average. Finally, the results offlood spreading increased vegetation cover and production forage in dams.
J. Sharifi; M. Akbarzadeh
Abstract
A major part of the rangelands of Iran are located in arid and semi-arid regions. In this climate, rainfall fluctuation is an important factor which affects vegetation and forage production. In dry years that rainfall decreases, surface vegetation and forage production is damaged. This study was conducted ...
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A major part of the rangelands of Iran are located in arid and semi-arid regions. In this climate, rainfall fluctuation is an important factor which affects vegetation and forage production. In dry years that rainfall decreases, surface vegetation and forage production is damaged. This study was conducted on semi-steppic rangelands of Ardebil over nine years (1999-2007), to study of vegetation changes with rainfall fluctuation. The results showed that canopy cover of Salsola gemmascens and Noaea mucronata species was decreased but Artemisia fragrans and Kochia prostrata species were increased.Generally density of shrub species was decreased about 40% and showed a positive correlation with seasonal precipitation (fall and winter). Grass species showed different response to precipitation changes over nine years period and in general, no significant changes were observed. Stipa hohenackeriana species was affected by winter precipitation but Poa bulbosa and Cynodon dactylon were correlated with spring precipitation. Density of perennial forbs species was increased considerably (about seven times), but in dry years (2000-2002) forage production reduced. Forage production over nine years increased from 296 kg to 747 kg per hectare, which is approximately 2.5 times higher. Meanwhile, proportion of plants in classes I, II and III, were respectively, 23.1, 51.9 and 25.2 percent of forage production. Also, forage production in wet periods increased from 747 to 1968 kg per hectare which shows an increase of about seven times.
M.A Zare Chahouki; A Zare Chahouki; M Zare Ernani
Volume 63, Issue 3 , December 2010, , Pages 331-340
Abstract
The objective of this research was to study the relationships between edaphic and topographic factors with distribution of plant species. For this purpose, current study was conducted in Eshtehard rangelands of Tehran province. The sampling method was randomized–systematic and in each sampling unit, ...
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The objective of this research was to study the relationships between edaphic and topographic factors with distribution of plant species. For this purpose, current study was conducted in Eshtehard rangelands of Tehran province. The sampling method was randomized–systematic and in each sampling unit, three parallel transects with 750 m length containing 45 quadrates (according to vegetation variations) were established. Quadrate size was determined for each vegetation type using the minimal area; hence suitable quadrate size for different species was determined 1*2m (2 m2). Soil samples from the beginning and end of each transect at two depths 0-30 and 30-80 cm were taken and the measured soil properties included gravel, texture, organic matter, lime, pH and electrical conductivity. To analyze the environmental data, PCA was considered. The results indicated that gravel, texture, EC and lime play the main role in the distribution of plant species.
