Fire behavior in Pinus halepensis thickets: Effects of thinning and woody debris decomposition in two rainfall scenarios

Contrasting Effects of Fire Severity on the Regeneration of Pinus halepensis Mill. and Resprouter Species in Recently Thinned Thickets

“…Concerning the presence of remnant slash in the thinned stands, several studies have suggested that it may increase fuel availability, raising the probability of more intense and extensive wildfires in the future [44,45], although these studies refer to mature forest and most of them have not experimentally tested or observed these potential effects. Interestingly, our results indicate that surface fuel (slash) in thinned plots did not increase fire severity, at least at the tree level (see [19]). Moreover, this effect was obtained in spite of the short interval between thinning and wildfire (ca.…”

“…1000 trees·ha −1 during the thinning operations and a mosaic of thinned and un-thinned areas, with the aim of assuring enough seed availability and seedling recruitment in case a new fire occurs [9]. Of course, this recommendation should also be confronted with the higher fire intensity and severity observed in the stands with larger basal area (this study, [19]), stressing the need to adapt the management of these thickets to the landscape characteristics both to ensure their resilience but also the reduction of fire spread. Moreover, regeneration will depend not only on the previous density of pines but also on the weather conditions just after fire and on post-fire management decisions (e.g., salvage logging, drag of trunks), which may enhance or reduce the recruitment values found [49,50].…”

“…The lower fire severity observed in the thinned plots is probably related to the reduction of crown overlapping and ladder fuel (contiguous vertical fuels) after thinning [20,23,42,43]. In fact, in a companion study conducted in the same study area, it was observed that thinning reduced fire spread rate, fire intensity at the frontline, and especially flame length from 9.5 ± 0.2 m to 1.6 ± 0.3 m compared to the un-thinned areas [19]. Interestingly, these results match with the fact that we observed many pines still bearing brown needles in the thinned areas (Level 1 of Severity) but almost none in the un-thinned stands.…”

“…two months) when fine fuels were still very abundant (see Figure 2A). Simulations of fire behavior, considering the rate of slash decay measured nearby, suggests that in 2-3 years, fire behavior parameters will be even lower in the thinned thickets in comparison to the un-thinned ones [19].…”

Lessons Learned from Arson Wildfire Incidence in Reforestations and Natural Stands in Spain

“…Management implications useful for silvicultural treatments and for supporting restoration strategies and policies could be derived from the historical analysis of arson incidence, reinforcing some recommendations by other authors (e.g., [62]) and introducing other actions that may be quite relevant if future conditions evolve as expected in the socioeconomic and ecological environment of Spain. Fuel management is technically well developed in European Mediterranean countries and in Spain, and abundant literature exists on the application of prescribed burning, mechanical thinning or mastication [63,64], but treatments and effects are usually analyzed for individual species (i.e., P. nigra, Piqué and Domenech [65]; P. halepensis, Palmero-Iniesta [66]; P. pinaster, Molina et al [67] without considering stand origin. In agreement with these findings, aged, more mature forest structures and closed canopy cover generally lead to less severe fires in our models, even in Eucalyptus or P. pinaster stands, but not in P. halepensis, P. nigra and P. sylvestris forests if vertical fuel connectivity was present.…”