khadije naghizadeh; mohammad jafari; hosein azarnivand; mohamad ali zare chahiiki; Hamidreza Abasi
Abstract
The effect of environmental factors on vegetation diversity in Eshtehard rangeland was studied in present study. Sampling was done using Minimal Area method. To measure the plant properties in each type, regarding the extent of each type, three 500 meter transects with 50 meter intervals between transects ...
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The effect of environmental factors on vegetation diversity in Eshtehard rangeland was studied in present study. Sampling was done using Minimal Area method. To measure the plant properties in each type, regarding the extent of each type, three 500 meter transects with 50 meter intervals between transects (due to the scarce vegetation cover) were established. In each plot, the number and types of existing species and their percentages were determined. Also, profiles were dug at the beginning and end of each transect and soil specimens were sampled at 0- 20 cm depth. Among soil properties, the percentage of clay, silt, sand, organic matter, lime, acidity, electrical conductivity, calcium, magnesium, sodium and potassium were measured. After collecting data, Shanon-Winer species diversity and Simpson indices were determined using Ecological methodology Software. Finally, the most important factors effecting the species diversity variation were specified using Principle Component Analysis. The results showed that among the studied factors, elevation, slope, soil depth and lime are the most effective ones.
bahram choubin; SHahram KHalighi Sigaroodi; Arash Malekian
Abstract
Predicting climate trends, especially forecasting rainfall, provides managers of different fields withsuitable tools so that considering these predictions; they can devise future-state policies. At thisstudy, after selecting the most effective climate indices applying PCA method, the effects of largescaleclimate ...
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Predicting climate trends, especially forecasting rainfall, provides managers of different fields withsuitable tools so that considering these predictions; they can devise future-state policies. At thisstudy, after selecting the most effective climate indices applying PCA method, the effects of largescaleclimate signals in seasonal rainfall of basin Maharlu - Bakhtegan were investigated bothsimultaneously and by delay through statistical methods (Pearson correlation and cross-correlationcoefficient) and by applying stepwise regression model, regression equation for forecasting rainfallwas offered. The results showed that in cross-correlation between the time series of SPI (dependentvariable) at time (t) and climate signals (independent variable) at time (t-k), only SOI indexconcurrently has a significant relationship with rainfall, whereas, most of indices turned significantwith standardized precipitation index with different lag times. In season to season study of thesignals with the standard precipitation index using Pearson's correlation coefficient it was found thatclimate signals of spring and summer are not significantly correlated with SPI. Representationcoefficients (R2) and standardized regression effect (Beta) in stepwise regression model showed thatsimultaneous and with season to season delays signals (for example: SPI index of autumn with fourprevious seasons indexes) at method Pearson correlation have higher relationship with seasonalstandardized precipitation index than the cross-correlation in time (t-k), (which signals of allseasons given is delay together with than SPI of all seasons) show.
Seyedeh Zohreh Mirdeilami; Esmaeil Sheidai; Moosa Akbalou
Abstract
Considering the importance of vegetation changes and awareness of its destruction or improvement trends in programming and its proper managing of utilization, this study was conducted in order to survey the effects of grazing on the qualitative and quantitative components of vegetation (including life ...
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Considering the importance of vegetation changes and awareness of its destruction or improvement trends in programming and its proper managing of utilization, this study was conducted in order to survey the effects of grazing on the qualitative and quantitative components of vegetation (including life form, growth form, palatability class, plant families and species diversity) and recognition their most important changes in both grazing and enclosed sites in Kalpush plain, Golestan provience. For this purpose, samples were taken via 78 plot 1 square meter in a randomly- systematic method. Mean comparison of the components and recognition of the most changeable components in consequent implementing grazing management were done with t-student test and principle component analysis (PCA) respectively using Spss software. According to the vegetation study, 13 species belong to Asteraceae family and 10 species to Poaceae family and there are 69 Herbaceous species, 13 Grass species and 5 shrubs species of plants in this region. The results of t-Student test indicate an increase in relative density of Therophytes and class I plants, and decrease in Cryptophytes and class III in the enclosed. Also the results point out that grazing has caused increasing in the relative canopy of Shrubs and Champhyte and decreasing in Therophytes, Forbs in the region. Comparison of relative density and canopy cover of plant species in two sites showed a relatively good effect of rangeland enclosing in increasing of the density, restoration and recovery of species composition and diversity. Principal component analysis also showed that the most changeable components in consequent of rangeland enclosing were Forbs, Hemicryphtophyte, Therophyte, Appiacea and Brassicacea families in positive and Shrubs in negative of first axis. Also the Papaveracea and Asteracea families have the most incremental changes in the second component.
