Some Ecological Properties of Pistacia atlantica Desf. in Khojir National Park of Iran: Some Ecological Properties of Pistacia atlantica Desf. in Khojir National Park of Iran

Khojir national park is one of the oldest protected areas in Iran that is greatly considerable in terms of biodiversity and ecological values.Pistachio（Pistacia atlantica Desf.） communities,which create some woodland in this park,are unique because they grow tolerantly in a dry land,in the vicinity of Tehran capital.This research is about some ecological properties of Pistachio woodlands.The dominant community of the area is Pistacia-Amygdalus lycioides.The density of Pistacia is 86 per hectare.The density of Pistachio trees was greater in the higher elevation than in the lower one.In addition,the collar diameter and the height of trees in the higher class were less.The average density of Pistacia in plots in northern slopes was significantly more than southern slopes（at 5% level）,but the average collar diameter of them were more on the southern aspect.The distribution,diameter and height of pistachio trees were not significantly related to the percentage of slope.Among the soil variables,the saturated water percentage（SP）,N（total nitrogen） and texture of soil were effective factors which played significant role in ordination of plots containing pistachio.Considering the important role of P.atlantica forest stands in soil and water conservation in Iran,we should attach more importance to their protection and conservation,as well as activities such as road and dam construction,and garden establishment in such unique ecosystems.