Investigation of growth dynamics of Juniper Trees in two Protected and Grazing areas in Jeyshabad, Zanjan, Iran Using Dendrochronology Method

Juniper trees are the native conifers of Iran extends in large areas of the country and is a factor to prevent soil erosion. However, the problem of Iranian juniper forest is the lack of natural regeneration. Therefore, the purpose of this study was to investigate the regeneration status of juniper plants in Jeyshabad (North Zanjan) repository at different times by using of Dendrochronology. In order to do this research, two plots were identified randomly in the protected and grazing areas, and samples were taken from all trees in each plot using increment borer. After preparing sample surface, ring width of the trees were measured and cross- dated. The results showed that the number of trees in the protected area is more than the grazed one. The mean diameter at breast height (DBH) of the trees in the protected area was lower, but in terms of average age, they were older than the trees in the grazing one. In the protected area, the number of trees in the age group of 10-20 years was remarkable, which showed that it had regenerated in the last two decades; while in grazing area, regeneration was affected and no new trees were observed after the period 1986. It was concluded that grazing decreased the regeneration of juniper and the growth pattern of the trees also changed; in a way that does not follow the form of natural growth.