The effect of wildfire on the structure and water balance of a high conservation value Hualo (Nothofagus glauca (Phil.) Krasser.) forest in central Chile

The structure and water balance of an N. glauca forest were measured in the year before and for two years after the wildfires of January 2017. The aim was to investigate the relationship between changes in structure and in transpiration, canopy interception, soil evaporation and their proportional contribution to evapotranspiration. This forest recovered rapidly after the fire. After two months there was evidence of resprouting from ground level in all species and after four months regrowth was visible in the crown of N. glauca. One year after the fire the leaf area index of the overstorey had recovered by about 1.5 units and about 70% of all the trees were supporting live growth either at the base or in the crown. The overstorey sapwood area was 5 m(2) ha(-1) after the fire, down 60% from the 13 m(2) ha(-1) measured before the fire. In the year before the fire the total transpiration, canopy interception and soil evaporation were respectively 210 mm, 258 mm and 46 mm (evapotranspiration of 514 mm). In the first and second year after fire transpiration was 78 and 127, canopy interception was 145 and 85 mm and soil evaporation was 125 and 143 mm. Compared to before the fire, transpiration after the fire was reduced by 63%, canopy interception was reduced by 44% and soil evaporation increased approximately three-fold. The combined effect of all these changes in the partitioning of rainfall was a 33% reduction in evapotranspiration. The reduction in transpiration was in proportion with the reduction in sapwood area and was partially offset by a threefold increase in soil evaporation. Two years after the fire the water balance of this forest had substantially recovered and at the current rate of recovery will be at pre-fire levels in 2021.