ارزیابی جمعیت های مهمترین گندمیان علوفه ای چند ساله در مناطق مختلف رویشی کشور

Vegetation is one of the most important componenets of natural resources which play an important role in the expected capabilities and potentials and climatic charesteristics and dominant elements that are a crucial role in the distiribution and formation of vital phenomena. Astragalus is occupied about 31.4% of Esfahan province. One of the important species in province is Astragalus verus. In this study, climatic charecteristics are investigated to study the effective climatic factors on distribution of this specie. For this aspect, in this study 56 variable were used in the month of January, March, July and annual scale and to reduce the number of variable and determining effective factor was used factor analysis using by principal componenets analysis. The result showed that four factors of cooling temperature-humidity, precipitation-thunder, cloudy and wind are include 39.05%, 32.77%, 11.44% and 8.33%, respectively and 91.88% of the total variance of the data and the cooling temperature-humidity factor has the greatest impact on presence of this specie, so that, in areas, where this species can be seen, the cooling temperature-humidity factor was positive and which is negative in regions without this species. Also, the imperession made by natural resources expects showed that the highest percentage of desiccation observed in Naein and investigation the trend of climatic parameters in this area showed that the temperature parameters and wind are increase and precipitation is decrease. According to the optimal conditions of Astragalus verus, increasing temperature and decreasing precipitation have a negative impact on severity of desiccation, so that, desiccation percentage is 25%. In general, it can be said with regarde to the area of study that is equivalent to 106179 Km2, climatic factor have affected along with other factors and most likely, because of climate change that is not the most severe is that the region is affected by the micro-climate and Astragalus verus in terms of adaptation range is not sensitive to small variables of climate.Keywords: Astragalus verus, climate variables, factor analysis, trend, desiccation and Esfahan province