ardavan ghorbani; ardeshir pour nematy; zohreh sadat ghasemi; aliakbar shokuhian
Abstract
The aim of this study was identifying the effects of environmental factors on the distribution ofDactylisglomerataand Thymus kotschyanusin rangelands of Khalkhal and Kosar counties in the southern part of Ardabil province. From 111 selected sites, random systematic sampling was done using five 1m2 plots ...
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The aim of this study was identifying the effects of environmental factors on the distribution ofDactylisglomerataand Thymus kotschyanusin rangelands of Khalkhal and Kosar counties in the southern part of Ardabil province. From 111 selected sites, random systematic sampling was done using five 1m2 plots along a 40 m transect. In all sites, land cover parameters including stone and gravel percentage, bare soil, litter, and density of selected species were recorded. Soil samples were taken from the 0 to 30 cm of soil surface of each transect. Soil parameters including pH, organic carbon, potassium, phosphorus, electrical conductivity, Sand, Clay, and Silt were measured. One way ANOVA was used to study the significance of relationship between the effective environmental factors on the presence and absence of the selected species.Duncan's test was used to compare the measured factors.To determine the importance of measured variables on the distribution of selected species and grouping of sampling sites, canonical discriminant analysis was used. Results showed that variables of elevation, slope, temperature, rainfall, stone, gravel, litter, electrical conductivity are significantly different when species exist in contrast to the time that it does not exist (p<0.01). D. glomerata is mostly distributed on north aspect, and on sloppy areas, and the areas with the high litter, clay and organic matter, and T. kotschyanus is mostly distributed on west aspect, and on the areas with the high amount of sand, stone and gravel, and silt that create a good condition for the growth of this species. According to the results of canonical discriminant analysis, two functions with 77.8 and 22.2% and they explained totally 100% of the variance of data, and generally 94/4% of grouped cases, were correctly classified. Overall, the results of canonical discriminant analysis show that electrical conductivity, litter, precipitation, temperature, elevation, potassium, silt and bare soil are the most important variables in the distribution of D. glomerata and T. kotschyanus. Considering these results, better decisions can be made about management, restoration, and reclamation of rangelands.
