Evaluation of Spatial distribution pattern of tree and shrub species in a central Zagros (Case study: Chahartagh forest reserve)

To provide the initial database of this study, a 53-ha forest reserve in central Zagros was 100% surveyed by recording the location, height and crown coverage of the entire trees and shrubs including Brant`s oak (Quercus brantii), Syrian ash (Fraxinus rotundifolia), Persian juniper (Juniperus polycarpos), hawthorn (Crataegus Spp.) and Montpellier maple (Acer monspessulanum). The data was used to calculate species-specific values of five distribution pattern indices including C, Johnson-Zimmer, Pielou, Eberhart and Hiens indices. In addition, visual estimation and a so called Free Growth Index (crown area to height ratio) were applied for accuracy assessment of the calculated pattern indices. Results revealed a random pattern distribution for ash, as well as a clumpy distribution of oak and hawthorn trees. Distribution patterns of the remainder of species could not be fully described by majority of indices, which is attributed to the existing low density of maple and high epinastic control for juniper communities. The C index exceeded the other indices in describing the overall tree distribution patterns, and is therefore suggested to be used for highly diverse Zagros tree species.