[1] Aalto Univ, Dept Elect & Nanoengn, POB 15500, Aalto 00076, Finland
[2] Univ Helsinki, Dept Forest Sci, Latokartanonkaari 7,POB 27, Helsinki 00014, Finland
[3] Southern Illinois Univ, Dept Geog & Environm Resources, 1263 Lincoln Dr, Carbondale, IL 62901 USA
[4] Univ Minnesota, Dept Forest Resources, 1530 Cleveland Ave N, St Paul, MN 55108 USA
[5] Swiss Fed Inst Forest Snow & Landscape Res WSL, Zuecherstr 111, CH-8903 Birmensdorf, Switzerland