Short-term effects of forest fire on soil erosion in Korea: Case study of 2020 Andong forestfire

Forest fire can devastate forest landscape. After the fire excessive runoff and soil erosion might occur, thus turning once fully functional forestland into degraded forest without topsoil and nutrients. It is important understand how soil erosion changes and burned area recovers with time. This study accessed the short-term effects of forest fire on soil erosion by monitoring sediment yields during wet summer season after a fire, using a total of twelve 5m x 10m silt fences from canopy fire, ground fire, and control areas (no fire) in Andong where 2020 hectares of forestland were burned in April of 2020. All silt fences were located at east-facing hillslopes with 45–55% steepness and conifers. The soil texture of canopy and ground fire areas was sandy loam, and control area was loam. The four sediment observations were made during the monitoring: An average of 158.0 kg ha-1 from canopy fire area, 0 kg ha-1 from ground fire area and 0 kg ha-1 from control area with accumulated rainfall of 53.0 mm (on 7/4); 1,077.5, 28.4, and 8.3 kg ha-1 with 174.5 mm (7/17); 1800.0, 116.7, and 3.2 kg ha-1 with 275.5 mm (8/4–5); 2340.0, 22.0, and 27.5 kg ha-1 with 226.5 mm (8/25); 580.0, 1.9, and 0.7 kg ha-1 with 156.8 mm (9/14&16); and 12.3, 2.3, and 0.5 kg ha-1 with 3.1 mm (10/5–6). The results indicated extremely high soil erosion occurred from canopy fire area and minimal erosion occurred from ground fire and control areas where no significant difference was found. Conifers defoliated due to stress from ground fire and fallen needles provided ground cover, thus preventing soil erosion. The ground covers measured from canopy fire, ground fire and control areas were 27.5%, 82.4% and 99.7% on 7/3 and 59.9%, 85.5% and 99.1% on 10/5, showing a large difference between canopy and ground fire areas with conifers. This study showed the importance of ground cover to mitigate post-fire erosion, and erosion control measures, such as mulching, should be considered to increase ground cover. Keywords: forest fire; ground cover; postfire soil erosion; sediment; silt fence ID: 3486822