Mohammad hosein parsamehr; zahra khoravani
Volume 24, Issue 1 , May 2017, , Pages 16-29
Abstract
This research was aimed to classify the drought in arid and semi arid regions of Isfahan province using TOPSIS technique. Four climatic elements including temperature, number of rainy days, annual rainfall and relative humidity were used for five meteorological stations during the 20-year period (1994-2013). ...
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This research was aimed to classify the drought in arid and semi arid regions of Isfahan province using TOPSIS technique. Four climatic elements including temperature, number of rainy days, annual rainfall and relative humidity were used for five meteorological stations during the 20-year period (1994-2013). For validation of the proposed method, the output of TOPSIS method was compared with the output of DPI, PNPI, RAI and SPI. For this purpose, Spearman's rank correlation coefficient was used between the quantified values of drought severity index and annual rainfall. The results showed that there was a strong correlation between the drought severity index and annual rainfall in the TOPSIS algorithm in all studied stations. Therefore, the validity of the model was approved. Generally, moisture fluctuations are high in the study area. In other words, drought is completely independent from station to station and from year to year, so that Nain and Isfahan had the highest (13 years) and lowest (7 years) number of drought years, respectively. In the TOPSIS algorithm, drought is closer to its real value since more parameters are used compared with previous simple methods. In this method, there is a systematic relationship between climatic elements in a year and other years, through which evaluation and ranking of drought is carried out. Finally, it could be concluded that the TOPSIS algorithm is a method capable of determining and ranking drought.
Amir Hosein Parsamehr; Mohammadreza Vahabi; zahra Khorovani
Volume 22, Issue 1 , June 2015, , Pages 194-203
Abstract
Vegetation cover is one of the most important factors for ecosystem sustainability; thus, recognizing and understanding factors affecting the establishment and distribution of vegetation communities are necessary. This study was aimed to determine the relationship between vegetation and soil parameters ...
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Vegetation cover is one of the most important factors for ecosystem sustainability; thus, recognizing and understanding factors affecting the establishment and distribution of vegetation communities are necessary. This study was aimed to determine the relationship between vegetation and soil parameters of Ardestan rangelands, Isfahan Province. Primarily, the vegetation types were distinguished in the field using physiognomic method. Plot size was determined applying minimal area method. The number of plots was determined using statistical method. Systematic randomized sampling was used and performed along three transects of 100 m length. Ten plots of 6m2 were established along each transect at 10-meter intervals. Three soil profiles were dug in each area and soil samples were taken at a depth of 0-150 cm to study 21 soil factors. The results of factor analysis showed that among variables studied, 17 variables were the most effective factors on vegetation types of the study area. To determine the effect of environmental factors on the establishment of vegetation, canonical correspondence analysis was used applying CANOCO software. Ordination results showed that environmental factors such as soil texture, lime, potassium and electrical conductivity had the most important role in the establishment and expansion of plant communities in the study area.