1. Dept. of Natural Resources and Environmental Engineering, School of Forest Engineering, Univ. of Vigo, Campus A Xunqueira s/n, 36005 Pontevedra, Spain (corresponding author).
2. Dept. of Natural Resources and Environmental Engineering, School of Forest Engineering, Univ. of Vigo, Campus A Xunqueira s/n, 36005 Pontevedra, Spain.