Application of Ripley's K-Function in Detecting Spatial Pattern of Wych Elm Species in Khayroud Forests, North of Iran

One of the most important characteristics of plant communities is spatial pattern of trees. Spatial pattern of trees are important structural characteristics of forests that their studies have extensive applications in sustainable forest management. Quantifying the spatial structure is an important component in describing natural ecosystems. Because of its importance as threatened but valuable species, spatial pattern of Wych elm has been studied in order to help its management and restoration. The current research was done in Namkhaneh District, Khayroud Forests belonging to University of Tehran. Due to the extent of study area (1035 ha) and being dispersed in the area, the location of Wych elm trees larger than 10 cm in DBH was recorded by Global Positioning System. Spatial pattern of elm trees has been analyzed using univariate K-Ripley function. The results showed both whole population and small size trees had clumped distribution at the scales < 10 m and this species tend to have random pattern at greater scales. In order to investigate if clumped pattern at small scales is due to seed trees or not, all of measured trees were assigned into four diameter size classes as small, medium, large and extra-large timbers. Spatial association among small size class and other classes were analyzed using bivariate Ripley’s K-function. Results showed there exists repulsion between small size classes and other classes and it seems suitable site conditions, reluctancy of illegal cutters to small-diameter Wych elm trees and interactions with other species are responsible for clumped pattern at smaller scales.