Efectivitat dels tractaments d'aclarida en la reducció del risc de propagació d'incendis en regenerats de pi blanc
Authors:   , Domenech Jardí Ruth 
Published: September 2023

Increased wildfire activity over the last years has made fire managers to become more concerned about the effectiveness of
current fuel treatment practices to reduce fire risk and severity. Fuel treatments lead to changes in the forest structure and
therefore modify certain basic parameters that may influence the fire behaviour.
The goal of this work is to quantitatively assess the effectiveness of fuel treatments in reducing risk of wildfires spread in
some typically Mediterranean forest. Specifically, it envisages to know the characteristics of the fire that can occur in the slash
originated from regenerated aleppo pine stands that were thinned after a wildfire and also to know the evolution of slash
combustibility after the treatment.
First, an extensive literature review has been done, focused mainly on those works that assessed the effectiveness of fuel
treatments in reducing the risk of wildfire. Several studies demonstrated the effectiveness of treatments such as prescribed
burning or thinning. However, these studies are not consistent about what treatment and slash management technique are
the most effective.
A study area has been selected and located within the perimeter of a large forest fire occurred in Bages (Central Catalonia,
Spain) in 1994 to study the effectiveness of a type of fuel treatment usually performed in the Mediterranean Basin. The site
was previously thinned during different periods and the slash was left in, not managed. In this area, the fuel, environment and
topographic characteristics have been determined. With the fuel sampling methods used at the site, a protocol has been
produced in order to characterize the regenerated aleppo pine stands, useful to obtain the parameters needed to evaluate fire
behaviour. Results have led to a new fuel model for regenerated aleppo pine stands and also fuel models for regenerated
aleppo pine stands that have been thinned at different times with the slash remaining unmanaged at the site.
An experimental burning program has been implemented reproducing two different regenerated structures (6 and 40 months
after treatment). With these experiments it has been proved that ex-situ experimentation is not useful to reproduce actual fire
situations because it is impossible to repeat faithfully the overall structure of the ecosystem that affect fire behavior. A series
of simulations of potential fires that could occur in the study area have been performed, incorporating the determined inputs
(environmental conditions and fuel type) and evaluating different simulation tools (NEXUS i WFDS). Results obtained with the
two simulations tools used confirm that both tools are reliable. In general values obtained in fireline intensity and rate of
spread with WFDS are larger than with NEXUS. Results from simulations of Bages plots carried with both simulation tools
generally show that fire behavior is more severe 1 month and 6 months after the treatment. That is, the wildfire effects after
the treatment would be worse than in the untreated control plot and that time does not improve this situation, at least six
months after treatment. According to the results and given the characteristics of our country where the risk of fires is very high,
the effect of thinning treatments performed in central Catalonia after the 1994 fire brings a great fire vulnerability in treated
stands, at least during the first months of treatment.