The effects of soil burn severity on initial establishment of maritime pine in burned areas are not well known. Many factors may interact in the field, thus making it difficult to determine the exact role played by soil burn severity in the post-fire regeneration process. Monoliths of two contrasting soils – an acid, coarse-textured soil, with high organic matter content, and a neutral heavy-textured soil with low organic matter content – were experimentally burned to provide two markedly different levels of soil burn severity. The burned monoliths were sown with Pinus pinaster seeds and then placed in a greenhouse under a preselected water regime to determine the effect of burn severity on emergence and initial establishment of pine seedlings. High soil burn severity in the coarse-textured soils delayed germination, increased mortality and temporarily decreased the height of pine seedlings in the first year after sowing. This response was affected by: soil heating level, soil C consumption, post-fire soil C, depth of burn and post-fire duff-depth. Ash had no influence on the above processes. These factors did not explain the variability in the response of regeneration variables in the heavy-textured soils. The applicability of the results to field conditions is discussed.

Suppression fires are frequently used in wildland firefighting operations. However, little is known about how suppression fires behave and how the main front and the suppression fire interact. Lack of information limits the operational use and effectiveness of suppression fires and compromises the safety of firefighters. A series of experimental fires were conducted in a shrubland fuel complex in Galicia to quantify the effect of the interaction between a heading fire burning upslope with the prevailing wind and a suppression fire burning downslope from a control line against the wind. An empirical model was developed to estimate the possible effect of interaction between fronts on the rate of spread of both fronts. For heading fires, the explanatory variables were: wind speed on the windward side of the fire, distance between fronts and slope angle. In contrast, for suppression fires, the only significant explanatory variable was the distance between fronts. The models reflected the observed low to moderate acceleration in the rate of spread of both fronts and the short distance over which interaction occurred (<20 m). The study revealed that the safe and effective use of suppression firing is more limited than previously expected. In fact, with moderately high wind velocities on flat and moderately steep terrain, the use of line firing appeared unsafe.