12Brief summary: The capacity of several fuel beds to be ignited by firebrands and to sustain a fire was assessed 13 through the study of their flammability. Then, the capability of different types of firebrands to ignite fuel beds 14 was studied through laboratory tests, in order to know their behaviour when they are involved in spot fires. 29A series of tests were conducted under laboratory conditions to assess, on the one hand, the capacity of several 30 fuel beds to be ignited by firebrands and to sustain a fire and, on the other hand, the capability of different types

No abstract

The effect of wildfire and the subsequent harvesting on soil degradation was evaluated in a burned Pinus pinaster stand in Galicia (NW Spain). During the first year following a fire of moderate intensity, burned trees were not harvested and soil erosion losses, measured by sediment collection at the bottom of bordered plots, were very low. An apparently limited impact of fire on soil and reduced rainfall erosivity for this period could be responsible for that result.Salvage logging took place 13 months after fire. Three post-fire alternatives were compared: no harvesting (standing burned trees), harvesting þ windrowed slash and harvesting þ slash chopping. Soil losses were even lower during the 14 months after these treatments than for the previous pre-harvesting period. Again, low mineral soil exposition and rainfall erosivity seemed to contribute to that result.Changes in soil bulk density and soil shear strength after clearcutting and slash manipulation were small and not enough to trigger sediment yield significantly.Harvesting and logging operations apparently increased soil inhomogeneities. This degree of variability was more adequately assessed by using micro-plot fences instead of plot fences. The percentage of soil disturbed by machinery was the variable most related with the observed minor soil losses after harvesting, at micro-plot level. This study indicated that the combined effect of wildfire and clearcutting caused only an acceleration of soil erosion when significant exposition of mineral soil occurred after these perturbations. However, these results must be taken with caution because rain erosivity during the study was low. To delay post-fire clearcutting until several months after the fire could reduce the impact of this forestry operation on burned soils, taking advantage of the natural mulch created by scorched leaves fall, although other issues must be taken into account.

No abstract

& Introduction Wildfires are considered the most important disturbance in the Mediterranean Basin, and some are propagated over long distances due to lift-off and ignition of firebrands. & Objectives To improve our knowledge of firebrands involved in spotting fires, flammability characteristics of eight types of firebrands commonly generated by wildfires in Southern Europe were determined under laboratory conditions. & Results All the firebrands tested showed 100% ignition frequency but with a wide range of time to ignition and flaming duration. Weight loss during combustion was exponentially related to time, and there was a decrease in the ratio of the weight at temperature T to the initial weight with increasing temperatures. In our experimental conditions, there was a significant effect of fuel moisture content on time to ignition, flaming duration, combustion and thermal decomposition. On the basis of the characteristics analysed, three firebrand groups have been identified in relation to spotting: heavy firebrands with ability to sustain flames, efficient for long-distance spotting (pine cones); light firebrands with high surface-to-volume ratio, efficient for short-distance spotting (leaves and thin barks); and light firebrands with low surface-to-volume ratio, efficient for short and, occasionally, long-distance spotting (all the other types of firebands).