Formation of Post-Fire Water Repellent Layers on Nothofagus glauca (Hualo) Forests, After the Historical “Las Máquinas” Wildfire in South-Central Chile

Abstract

The Chilean summer of 2017 was the worst wildfire season by far. Hundreds of wildfires burned a total of more than half a million hectares of forested land (native forests and forest plantations). A significant portion of the burned area was occupied by Hualo (Nothofagus glauca (Phil.) Krasser), a native forest species widely distributed in central Chile. Using the water-drop-penetration-time method, post-fire water repellency was evaluated at different depths (on the mineral soil surface and 5 mm below it) for a Hualo stand. Comparative data were obtained from a neighboring 11-year-old Monterrey pine (Pinus radiata D. Don) plantation. Both stands were located near Santa Olga, one of the towns that were totally consumed by the wildfire. A Chi-Square statistical analysis was used to determine significant differences among stands and soil depths. Results suggested that the abundant Hualo native forest species exhibited strong potentials to form fire-induced water repellent layers. Differences were mainly in depth between the two species. As wildfires in Chile are expected to increase in frequency and intensity, the authors strongly recommend post-fire flood control practices on Hualo-burned drainage areas located upstream from human settlements, as well as erosion and sediment control techniques to avoid post-fire desertification processes.