Location and description of the arboreta used in this study (triangle symbols) on a background map of tree cover in 2000 (Hansen et al. 2013). For each arboretum, the following characteristics were obtained: Year = year of first plantings, Nsp = number of alien conifer species planted in the arboretum, MAR = Mean Annual Rainfall between 1981 and 2010 obtained from the Royal Meteorological Institute of Belgium (RMI, n.d.), and Alt. = Altitude (m).