Investigation and Determine of Ecological Characteristics of Sites of some old Broad-leaf and needle-leaf Trees in Zagros forests (Case study: Forests of Ilam Province)

.  Introduction Old trees are important and key elements of forest sites and are of great value in terms of forest management, reforestation, silviculture and ecology. Although old trees constitute a small percentage of forest trees, they account for a large share of forest carbon reserve and play a vital role in carbon storage. Understanding the how geographical and site distribution of these trees across the forest is essential to obtain information for forest restoration management. Therefore, this study was carried out to investigate the geographical and site characteristics of old trees of Wing nut, Ash, Hackberry, Sycamore, Elm, Olive, Cypress and Fig in Ilam province.   Materials and methods After querying the villagers and local people and conducting numerous forest surveys, the old trees were identified and selected on the basis of the diameter of the breast. Then their geographical characteristics including city, district, village, geographical coordinates and site conditions including slope, aspect, altitude, soil depth, climate and proximity to water source were measured or recorded. Results and discussion The results showed that in terms of geographically distribution, the identified old trees have located in Ilam, Mehran, Malekshahi, Badreh and Dehloran cities. Topographically, the old trees of Wing nut, Elm, Ash and Fig were located in the 0-10% slope class, Hackberry and sycamore in the 0-10% and 10-30% slope classes, olive in the 10-30% slope class and Cypress in the 40-70% slope class. The old trees of Wing nut, elm, Ash and Hackberry were located in the north aspect, fig, sycamore and Cypress in the south aspect and olive in the west and south aspects. The old trees of Wing nut, elm, Ash, Hackberry, Sycamore and Cypress were dispersed at altitude class of 1100–1250 m and olive and fig old trees were at altitude class of 1250–1400 m above sea level. Climatically, the old trees of Wing nut, elm, Ash and Hackberry were located in the very cold Mediterranean climate, Cypress trees and some sycamore trees in the cold Mediterranean climate, and fig, olive and some plantain trees were in the semiarid cold climate. In terms of access to water resources, old trees of Wing nut, elm, Ash, Sycamore, Hackberry and Fig were located on the bed or margin of river, old Cypress trees had no access to water resources and some olive trees were close to water resources. In terms of soil subsidence, old trees of Wing nut, elm, Hackberry, olive, and fig were mostly in soils with medium depths. Old ash and sycamore trees were present in shallow to medium depths and old cypress trees were present in shallower soils. Although the identified old trees were present in limited sites, their long-term and sustained presence in these sites indicates that sites conditions are favorable for their survival. Conclusion Therefore, it can be concluded that the presence of low slopes, suitable soil bed and access to water resources were desirable characteristics for stability and survival of the studied old trees in these sites. Due to the above-mentioned characteristics, ecologically similar sites can be found in the forests of the province and can be restored by seed of old and resistant trees. Keywords: Site, Topography, Climate, Geography, Old trees, Ilam