Modeling response curves of European yew (Taxus baccata L.) using HOF models along the environmental gradient in north of Iran

Abstract

One of the important issues in plant autecology is the analysis and understanding of species-environment relationships and response of species to ecological gradients. Understanding how species respond to environmental variables is useful for predicting the environmental and geographic distribution of species. The main objective of this research is to study the response curve of European yew to identify the most important climatic and physiographic gradient in the northern forests of Iran. In the present study the Huisman–Olff–Fresco function (HOF) was used to study the response curve of the European yew in relation to each of the environmental variables individually and extract the optimum values. In order to select the optimal model, the Akaike Information Criterion (AIC) was used. Based on the results of this study, 41% of the models have either monotonically increasing or decreasing behaviors (models 2 and 3), 27% of the models have a unimodal symmetric behavior and 32% of models have a skewed behavior. European yew in 59% of models has a unimodal response curve. Based on the variables used in the study, it can be said that the European yew is a species that prefers oceanic climates, midlands altitudes, and north-facing slopes for establishment in temperate forests of Iran. Together, these findings advance niche theory about the European yew tree and may be used for generating better predictive models of European yew distributions under future climate change.