Implementation of uniform angle index in determination of trees spatial pattern in a forest reserve of Hyrcanian zone

Spatial pattern is a key attribute of forest ecosystems. Recently, spatial distribution pattern of woody plants, especially trees, has gained many interest by plant ecologists which leads to introducing a large number of different methods for quantifying spatial patterns. In this topic, finding the easiest method for data collection and analysis has always been a major concern. The aim of this research is evaluating of Uniform Angle Indexability in determining spatial pattern of trees in a Hyrcanian forest. For this purpose, an area of 18 hectares in a forest reserve of Populus caspica was selected and surveyed by full callipering method, and stem-map of three major species including Fraxinus excelsiorsubsp, Populus caspica Born and Petrocarya fraxinifolia (Lam.) was prepared. At first, spatial pattern of all species was determined by Nearest Neighbor Index and the determined pattern was considered as an actual spatial pattern of the trees. For calculating Uniform Angle Index, 3, 4 and 5 neighbor trees around central randomly were chosen and the angles created between them was measured. Finally, obtained results of Uniform Angle Index were compared to the results of Nearest Neighbor Index. The results showed that in all cases, the determined spatial pattern Uniform Angle Indexwere similar to Nearest Neighbor Index. Based on the results of this study, Uniform Angle Index a quick and cost effective method which can be used for describing spatial pattern of trees in similar forests.