Ali Vosough; Ali Ashraf Jafari; Ezat Karami; Reza Talebi; Houshmand Safari
Volume 29, Issue 3 , October 2022, , Pages 231-240
Sakineh Lotfinasabasl; Mohammad Khosroshahi; Zahra Saeedifar; Fatemeh Dargahian
Volume 25, Issue 4 , February 2019, , Pages 923-943
Abstract
Precipitation temporal trend analysis and study of the drought condition have been of great concern during the past century because of the attention given to global climate change by the scientific community. The aim of present study was to investigate and analyze the rainfall trends and its affected ...
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Precipitation temporal trend analysis and study of the drought condition have been of great concern during the past century because of the attention given to global climate change by the scientific community. The aim of present study was to investigate and analyze the rainfall trends and its affected drought conditions in Jazmurian basin using non-parametric mann-kendall method and multidimensional comparison of drought indices including Standardized Precipitation (SPI), deciles (DI), the percentage of normal (PNI), Chinese Z (CZI) and the Z score (ZSI) with rainfall data from 24 gauged stations for the period of 1983 to 2013. For this, the drought indices were calculated, and then categorization was performed on the basis of similarity and correlation using cluster analysis method. The results proved a positive and significant increase in the rainfall amount of 1992-1993 and 1995-1996 years. Statistical analysis showed that the highest amount of rainfall occurred in the years of 1992-93, 1995-96 and 2004-2005 and the lowest in the years of 1983, 2000, 2003 and 2005 in the basin. Cluster analysis showed that the ZSI and PN indices with similarity of hundred percent in the diagnosis of wet and dry periods, intensity, duration and continuity were completely similar and had the highest similarity among all the groups. The CZI and SPI with 99.5 percent similarity were in the second level of similarity as well. Validation of the results through the numerical comparison of SPI and CZI indicates the same trend of two indicators and little differences in presenting the drought conditions of Jazmorian basin. However, in assessing the severity of droughts, CZI showed more severe drought condition. Overall, the results showed a greater focus of the drought in the southern east and southern parts of the basin indicating the high probability of drought occurrence potential of the basin. Therefore, the study of drought through CZI and SPI indices in the basin of Jazmorian is suggested for the proper policy making and management of water resources regarding conservation and increasing of the productivity from environmental, economic and social point of views.
shahla Ghaderi; Alireza Amirian Chekan; Amaneh Karim Zadeh; Masoume Difrakhsh; Javad Pourrezaie
Volume 24, Issue 3 , October 2017, , Pages 478-493
sahar sabaghzade; Mohammad Zare; Mohamad Hosein Mokhtari; Mohamadreza Afkham olshoara
Volume 23, Issue 4 , March 2017, , Pages 843-855
Abstract
Arid land degradation is the biggest environmental challenges in 21st century. Saxaul (Haloxylon spp) is one of the most important species for sand dunes fixation, widely used in reclamation of arid lands. One of the applications of satellite data is to estimate the biomass of plants. In this study, ...
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Arid land degradation is the biggest environmental challenges in 21st century. Saxaul (Haloxylon spp) is one of the most important species for sand dunes fixation, widely used in reclamation of arid lands. One of the applications of satellite data is to estimate the biomass of plants. In this study, Landsat 8 satellite images were used for mapping the biomass of Haloxylon plants in the South Khorasan province. Then, 11 vvegetation indices (DVI, IPVI, NDVI, PVI, RVI, SAVI, TSAVI, WDVI, Brightness, Wetness, Greenness) were calculated. To determine the correlation between biomass and satellite data, 30 plots of 30*30 m 2 were used in the region and vegetation parameters were measured. Principal component analysis and cluster analysis were used to classify the indices. Finally, the effective indices were selected and the regression models were fitted. Results showed that the regression model obtained from the TSAVI index with RMSE of 14.9 and R 2 =0.43 had the best estimation for the above ground biomass of Haloxylon.
Jalil Karimzadeh; Hasan Monirifar; Akbar Abdi Ghazijahani; Ahmad Razban Haghighi
Volume 19, Issue 4 , March 2013, , Pages 693-702
Abstract
In order to study the grouping of Agropyron tauri populations, 13 populations were investigated in a randomized complete blocks design with three replications. The study was performed in research field of Islamic Azad University of Tabriz in 2010. In this study, a number of traits including plant height, ...
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In order to study the grouping of Agropyron tauri populations, 13 populations were investigated in a randomized complete blocks design with three replications. The study was performed in research field of Islamic Azad University of Tabriz in 2010. In this study, a number of traits including plant height, tiller number, leaf number, flag leaf length, first leaf length, second leaf length, first internode length, second internode length, crown cover, fresh yield, dry yield, fresh weight of single plant and dry weight per plant were evaluated. Analysis of variance showed significant differences among populations for all measured traits. Thirteen populations were classified into three clusters by cluster analysis of standardized data, based on Euclidean distance and Ward method. This result was in consistent with the height of geographic regions from which populations were collected. In principal components analysis, four components were introduced, and the traits of fresh and dry yield showed high and positive coefficients in first component. Results of cluster analysis were confirmed by results of principal components analysis.
Azadeh Asrari; Gholam reza Bakhshikhaniki; Abalfazl Rahmatizadeh
Volume 19, Issue 2 , September 2012, , Pages 264-282
Abstract
In this research relationship between vegetation and salt soil in Qom province was studied. The study area situated in central Iranian which is about 14631 km2 with Salt Lake. In this study, first considered region condition including the geographical position, geological history, pedology and ...
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In this research relationship between vegetation and salt soil in Qom province was studied. The study area situated in central Iranian which is about 14631 km2 with Salt Lake. In this study, first considered region condition including the geographical position, geological history, pedology and climate. The aim of this study was assessment of plant communities of area and their relationship with soil. Primarily the vegetation types were distinguished at the field with physiognomic-floristic-ecologic method. The species data were gathered with stratifield random sampling method using the 10m by 10m quadrats recording the species covers, litter, bare soil, stone and gravel cover in the quadrat. In this study were considered 11 soil factors in 48 types of rangeland. Using cluster analysis was separated 13 plant communities in the region. To determine the effect of environmental factors on the establishment of vegetation was used CCA ordination method using software CANOCO. Ordination results showed that environmental factors such as electrical conductivity (EC), lime, sodium (Na), potassium (K) and calcium(Ca), are studied the most important role in the establishment and expansion of areas plant communities. Also plants of Chenopodiceae family compared with plants of Poaceae family have efficient mechanisms of salt tolerance. In salt lands gradual change of soil moisture, zoning of different species and vegetation types to come in parallel strips. Thus topography of the ground, although small, are the main factors of soil chemical and physical changes, and naturally caused the formation of specific habitat for various plant species.
Mohammad Hasan vand; Ali ashraf Jafari; Ali Sepahvand; Shahram Nakhjavan
Volume 16, Issue 4 , January 2010, , Pages 517-535
Abstract
In order to compare yield and forage quality, six local genotypes of common vetch (Vicia sativa) were sown in two separate experiments under irrigated and dry land farming system using randomize complete block design with three replications in khorramabad agricultural research station during 2005 and ...
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In order to compare yield and forage quality, six local genotypes of common vetch (Vicia sativa) were sown in two separate experiments under irrigated and dry land farming system using randomize complete block design with three replications in khorramabad agricultural research station during 2005 and 2006. Data were collected for Forage fresh and dry matter (DM) yield, plant height and quality traits as: dry matter digestibility, (DMD), crude protein (CP), water soluble carbohydrates (WSC), crude fiber (CF), acid detergent fiber (ADF), neutral detergent fiber (NDF) and total ash. Results of combined analysis showed significant differences between two conditions for all of traits except DMD. The average values of DM (2.76 and 2.35 ton/ha), CP (24.8 and 21.6%), and WSC (10.9 and 12.9%) were obtained for Irrigated and drought condition respectively, indicated higher values of both DM yield and CP and lower values of WSC in Irrigated conditions. Genotype effect was significant for forage yield, plant height, WSC and NDF. Results of correlation coefficients showed that forage yield had positively correlated with plant height, WSC and CF and negatively correlated with CP. Whereas, WSC had positively correlated with DM yield, plant height and DMD and negatively correlated with CP, ADF, NDF and total ash. Using cluster analysis, 6 genotypes were classified into two groups. Using biplot diagram based on 5 droughtresistance indices, six genotypes were scattered. Talarizan (Azna) with average values of 3.1 and 2.7 ton/ha DM yield for optimum and dry condition, respectively had higher values in both conditions and recommended for cultivation in more rainy regions of Lorestan province. Genotypes of Torshabad (Doruod) and Fahre (Aligudarz) with average values 2.55 and 2.72 ton/ha DM yield, respectively for drought condition, were identified as tolerant to dryness and identified for cultivation in dry land farming system. Genotypes of Doruod and Bawki (Azna) with average values of 2.39 and 3.01 ton/ha forage production in irrigated condition recognized as sensitive to dryness and recommended for cultivation in irrigated conditions. Among the productive genotypes, Fahre with average values of 12.74% WSC had good forage quality.
Hamid reza Mirdavoodi; Hojat... Zahedi; Masud Shakoei; Javad Tourkan
Volume 13, Issue 3 , February 2006, , Pages 201-211
Abstract
The initial step of each phenomenon is complementary recognizing and understanding of its relationship with other effecting and affecting phenomena. Regarding rangeland vegetation as the first chain of nutrition in rangeland's ecosystems, recognition of its homogeneous areas and vegetation type classification ...
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The initial step of each phenomenon is complementary recognizing and understanding of its relationship with other effecting and affecting phenomena. Regarding rangeland vegetation as the first chain of nutrition in rangeland's ecosystems, recognition of its homogeneous areas and vegetation type classification seems necessary. The present study was carried out in order to determination the most effectiveness ecological factors on vegetation types using Multivariate data analyzing. For that vegetation type was determine of type using GPS together with field survey and drawing map of the areas on the 1/50000 scale. Some data layers for each of vegetation type including density and cover percentage, climate, the mean elevation classes, mean annual rainfall, the mean slop, mean annual temperature, land types and Geographical aspect of the areas were collected and analyzed using Statistica program package and the method of factor analysis. The results of factor analysis shows that between applied variable, three main variables including climate, land types, and Geographic aspect with Eigenvalues of 82.8 are the most effectiveness ecological factors on vegetation types. Using cluster analysis rangelands classified in to 22 groups of Markazi province. the groups were confirm by Discriminate Analysis method.