1. Area of Soil Science and Soil chemistry, E.T.S. Ingenierías Agrarias, University of Valladolid, Avda. de Madrid 57, Palencia 34071, Spain
2. Sustainable Forest Management Institute, University of Valladolid-INIA, Avda. de Madrid 44, Palencia 34004, Spain
3. Department Plant Production and Forest Resources, University of Valladolid, Avda. De Madrid 44, Palencia 34004, Spain
4. Sustainable Forest Management Institute, Faculty of Education, Department of Psychology, University of Valladolid, Avda. de Madrid 57, Palencia 34071, Spain
5. Institute of Forest Management, Department of Ecology and Ecosystem Management, Center of Life and Food Sciences, Technische Universität München, Hans-Carl-von-Carlowitz-Plaz 2, Freising D-85354, Germany