Modeling distribution of oriental beech (Fagus orientalis Lipsky) trees in riparian forest by HOF model

We modeled the distribution of oriental beech (FagusorientalisLipsky) stands to determine optimum ecological amplitude range along riparian forests of RamsarSafaroud riverside in Mazandaran province. Data were collected on transects which were perpendicular to the water flow on both river sides. Each transect was 200 m in length, with a 200 m distance between transects. On each transect five 400 m2 quadrats were laid in 50 m intervals. At each sampling location the number of beech individuals with a diameter at breast height (DBH) > 7.5 cm were recorded. In addition three soil samples per plot were taken from the upper 30 cm depth. Totally 44 transects and 220 quadrats were sampled. An extended HOF model implemented in eHOF package in R was applied to assess the response of beech to soil variables, and the corrected Akaike's information criterion (AICc) was used for model selection based on models associated with the lowest AICc values. The results showed that only 27.5% of the models obtained a symmetric normal response curve (model IV), whereas 72.5% of models showed linear and asymmetric (i.e. I to V) curves. However, the VI and VII models were observed in none of the results. We assessed the HOF models to be of high potentials to be further employed in similarly-structured riparian forests.