1. Research Group in Atlantic Forests (GIS-Forest), Department of Organisms and Systems Biology, Escuela Politécnica de Mieres (E.P.M.), University of Oviedo, C/Gonzalo Gutiérrez Quirós, Mieres 33600, Spain
2. Department of Forest Science and Landscape Architecture, Escola de Ciĉncias Agrárias e Veterinária, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal