Yaser Ghasemi Aryan; Hossein Arzani; Esmaiel Filekesh; Reza Yari
Volume 20, Issue 1 , June 2013, , Pages 1-10
Abstract
Determination of grazing capacity is considered as one of the most fundamental aspects of range management and understanding the effective factors on it is of utmost importance. Since the amount of forage production in a growth period is the basis for calculation of grazing capacity, in this research ...
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Determination of grazing capacity is considered as one of the most fundamental aspects of range management and understanding the effective factors on it is of utmost importance. Since the amount of forage production in a growth period is the basis for calculation of grazing capacity, in this research the estimation of production through the measurement of plant’s dimensions was investigated. For this purpose, the habitat of Artemisia siberi was determined and then 8 transects of 50 m length were established with 10 m intervals by random-systematic method. The height and diameter of 40 species of Artemisia siberi with different dimensions were recorded and the production of each species was clipped and weighted after drying. All data were analyzed by SPSS. Results showed that there was a significant linear correlation between production as a dependent variable and volume, canopy cover and height of Artemisia siberi as independent variables (R2= 0.88, 0.84, and 0.74, respectively) at 1% probability level. Finally, the relationship between production and volume was identified as the best linear relationship.
Morteza Abtahi; Abdollah Seif; Mohammad Khosroshahi
Volume 21, Issue 1 , June 2014, , Pages 1-12
Abstract
Temperature and precipitation are basic constituent components of the climate of a region. For this reason, the assessment of present and future trends of these elements have been considered by different scientists such as natural resources or environmental experts. In this study, Namak lake basin was ...
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Temperature and precipitation are basic constituent components of the climate of a region. For this reason, the assessment of present and future trends of these elements have been considered by different scientists such as natural resources or environmental experts. In this study, Namak lake basin was divided in to six sub-basins and then monthly precipitation and temperature data were collected and reconstructed from 1956 to 2005. Average precipitation, maximum and minimum temperatures of sextuple sub-basins of the lake were calculated using Thiessen method in Arch Map software. In order to evaluate the precipitation trend, Standard Precipitation Index (SPI) was used. The trend of climatic factors (temperature and precipitation) was studied by linear regression and Mann-Kendall test. No significant trend was observed in standardized precipitation of the Namak Lake and in its sub-basins except in the sub-basin of Arak in which the trend of precipitation change was decreasing and significant. According to the study of monthly precipitation, strong droughts have been observed in sub-basins of Arak, Roodshoor and Karaj during the last 50 years. The trends of maximum and minimum temperature change were increasing and significant in most basins. Increasing the temperature of the Namak lake basin may be caused by several factors, including increasing greenhouse gases especially in big cities such as Tehran, Qom, Arak, Kashan, Hamadan, and Qazvin.