Soil Degradational Effects of Prescribed Fire,Central Portugal

摘要

Devastating fires in Portugal in 2003 and 2005 focused attention on prescribed (or controlled) fire as an important means of combating wildfire spread and/or reducing the fuel load. The soil degradational effects of controlled fires are generally considered relatively low, certainly by comparison with wildfire, but have received comparatively little attention. An experimental fire was carried out as part of the DESIRE research programme in February 2009 on a small (9 ha), steep, shrub-covered catchment in central Portugal. This paper considers hillslope-scale measurements of soil erosion, and losses of organic matter and selected nutrients using sediment fences installed pre-fire in the catchment, and following wildfire in July 2008 at a nearby comparable site. Rainfall amounts and intensities have been determined from tipping-bucket raingauge records. The 10-year soil erosion records from a sub-catchment weir and from a 16 m2 bounded plot installed in similar vegetation adjacent to the experimentally-burnt catchment provide long-term erosion records on long unburnt terrain. Temporal change in eroded material is considered with respect to rainfall characteristics and ground cover changes (assessed visually from 4 m2 plots and, using image analysis software, from repeat-photographs of 0.25 m2 plots). Implications for short-and long-term soil degradation of controlled fire are discussed.