به منظور بررسی تاثیر عوامل اقلیمی بر استقرار و درصد تاج پوشش گیاه استبرق در مراتع جنوبی استان فارس، 30 متغیر اقلیمی که دارای اهمیت بیشتری بودند، انتخاب شدند. متغیرها در نرم افزار SPSS نسخه 15 مورد تجزیه و تحلیل قرار گرفتند. با استفاده از روش تحلیل عاملی، دو عامل دما و عامل بارش استخراج شد که به ترتیب 39/44 و 41/42 و به طور کلی 81/86 درصد واریانس کل را توجیه میکنند. سپس با استفاده از همبستگی پیرسون و رگرسیون گیری ارتباطات بین متغیرها و تراکم و درصد تاج مورد بررسی قرار گرفت که بر اساس آن تراکم با عامل دما دارای همبستگی معنیدار و به صورت معادله درجه دو ارتباط رگرسیونی معنیداری نشان دادند. بر طبق نتایج به دست آمده، مهم ترین عامل در استقرار استبرق عامل دما بود. همچنین نتایج نشان داند متغیرهای اقلیمی مورد مطالعه تنها 36 درصد تغییرات تراکم درختچه استبرق را توجیه میکنند و مابقی تغییرات توسط دیگر عوامل محیطی کنترل میگردد.
عنوان مقاله [English]
An Investigation on Effects of Climate Factors on Density and Crown Cover Percentage of Calotropis procera, using Statistical Factor Analysis Case study, Southern Fars' Rangelands
Plant and Animal growth and distribution depend on environmental properties and their reciprocals affects. In world scale, climate is the most important geographic transmittal controller of plant species that traces direct and indirect on environmentâs elements effective on plants growth (Villers-Ruiz et al 2003). Other elements as soil, topography are other importance ((OâBrien et al, 1998),( Yaghmaei et al, 2009)). Dependence of plants on climate factors have been been reported by many scientists but quality and quantityâs state of these relationships are different in variants regions (OâBrien et al 1998, Balakram and chauhan 2005, Golfari et al 1978). In this study, Calotropis procera Is selected which is highly resistant to harsh climate conditions, presented significant protection of soil characteristics and economically important in the region. Cognition of plantâs Existential and ecological requirements, special climate, are very important in the plantâs development and expansion in arid and semi-arid abounded ecosystems. The main objective of this study is to characterize effects of climate factors such as temperature, precipitation and humidity on the plant density and crown cover percentage, using multivariate statistical analysis..
The study area is located in the southern township of Fars Province, he sampling method is based on a selective sampling procedure in a C. P. site in the region (zobeiri, 2007). 35 sites of C. P. have been studied in this study. The samples have been collected through a simple linear transect plan. The Plant Density and Crown Cover Percentage (CCP) have been calculated using field data measured in sampling plots. Accurate Position of each Sample plot has been registered using a hand GPS set and turn into GIS coverage by ARCGIS software package the monthly data, such as temperature, relative humidity and precipitations, collected by Synoptic and Climatology stations of Fars province have been employed in this study. Had be controlled accuracy of data of Synoptic and Climatology stations and then be estimated climatic variables by Inverse Distance Weighting interpolation method with accuracy more than (r=0.8) (Sergio et al, 2003). To investigate relationship between 30 climate and 2 plant variables, the data have been entered in a Principal Component Analysis and Varimax Rotation Methods of SPSS software.
The results indicated that density & Crown Cover Percentage depended on two factors, the humidity and temperature As shown in tab 86.81of total variance (table 1).
Table 1: Total Variance Explained
Component Crown Cover Percentage Crown Cover Percentage Crown Cover Percentage
Temperature 13.76 44.39 44.39
Humidity 13.14 42.41 86.81
The correlation between density and temperature is significant (p0.05) (table 3).
Table 3- the correlation results between CCP, precipitation and temperature factors.
Variable Temperature Precipitation
Density -0.4* -0.17 ns
Crown cover 0.28 ns 0.32 ns
*Correlation is significant at the o.o5 level
ns Correlation is not significant
Due to the results, temperature and humidity have a great influence in the establishment, density changes and, CCP of Calotropic procera at study area.
The correlation between density and temperature is significant. It shows that temperature has greater effect on variation of CCP that in the absence of Calotropic procera density. density changes in the northern provinces of Fars province where the climate is cooler. Results be confirmed with Quadratic regression and more density C.P in warmer regions.
There is no significant correlation between plant density and humidity factors not means that precipitation does not effect on C.Pâs growth and establishment, it is suggested that in areas with low rainfall and Plant in Dry region also has abilities to deploy and underground water is a greater dependence. The establishment of the C.P, rivers, surrounding roads and abandoned arable land (the author's observations) confirm that this And reports (2001) Francis and (2005) Brandes Parrotta also reported in 2001 based on plant growth in arid regions is consistent with the least rainfall of 150 mm.
According to regression results, only 36 percent of the density changes and the remaining variables are explained by other elements of climate change and other environmental factors such as soil (Sadeghian et al, 2010), the slope, wind speed and direction and ... Is justified. Given the importance of plant species for restoration,