Investigation of ecologycal parameters on the turn yellow of Haloxylon sp. (in the semnan province)

This project was done as a part of ecological and phonological studies of Haloxylon sp. This study was done in artificial habitat (Mohsenabad in Garmsar) and natural habitat (Chahjam in Shahrood) of Haloxylon sp. General information about condition of Haloxylon sp. habitats was gathered. Haloxylon stands were examined from different points including viability of seeds, dry matter in green, yellow and green- yellow stands. Phonological studies were done. In addition, soil physical and chemical properties were determined. Results indicated the direct and significant effect of precipitation and temperature on growth of Haloxylon sp. The other important factors were insufficient amount of major elements, unsuitable texture, the low distance between stands that caused strong competition between trees to get nutrients. The presence of rare green stands indicated their genetical resistance. It seems that the origin of these stands are form central desert region of Iran.