Short-term effect of fuel treatments on fire behaviour in a mixed heathland: a comparative assessment in an outdoor wind tunnel

Abstract

Fuel management is one of the main challenges for wildfire prevention in the Mediterranean region, where wildfires have important environmental and socioeconomic effects. Different treatments are usually applied in fire-prone shrubland to try to modify its flammability. However, a knowledge gap on the effectiveness of fuel management techniques still exists. We studied the effects of two mechanical treatments (shrub crushing and shrub clearing with removal) and of prescribed burning, on fire behaviour, and compared them with untreated vegetation. Experimental burns in 0.8 Â 6 m samples of regenerated shrubs 2 years after treatments were performed in an outdoor wind tunnel. All fuel treatments effectively modified fire behaviour, but no significant difference between treatment types was observed. Shrub fuel structure was the main factor affecting fire behaviour. Reduction of fuel load and height, especially necromass fraction, decreased flame height and fire intensity but did not affect fire rate of spread. Moisture contents of live and dead fuel fractions were not significant as independent parameters, but the average moisture level of the shrub fuel complex showed a relevant effect in determining fire behaviour. Temperature regime within and above the shrubs was also related to shrub fuel structure. This study contributes to understanding fuel management in shrubland by providing information about different fuel treatments effects on fire behaviour.

Effects of harvesting intensity and site conditions on biomass production of northern Patagonia shrublands

“…For example, harvesting biomass could also be an important management strategy for diminishing fuel continuity and wildfire hazard, the main disturbance in this type of Mediterranean ecosystems (Kitzberger and Veblen 1999), as has been largely studied for the Mediterranean basin (Madrigal et al 2016). Our results agree that biomass harvesting in these ecosystems only reduces fire hazard in the short term because shrubland species recover quickly (Marino et al 2011(Marino et al , 2014Fernández and Vega 2014;Fernandes 2015;Madrigal et al 2016) and mainly by a large bulk of fine fuels. In fact, our results show that increasing harvesting intensity of biomass (and potentially diminishing fuel continuity) produces a major production of fine fuel in the short term (potentiality increasing flammability); thus, this trade-off shows that the management of these communities for fire hazard reduction needs more complex solutions as previous works have discussed (Madrigal et al 2016).…”

Is Mechanized Harvesting of Shrubs Grown for Energy Purposes Environmentally Sustainable?

“…Our results point to even higher percentage reductions in this variable at all the locations, reaching values of around 60% at FB and 83% at NV, although in this case, the results correspond to the situation 2 years after harvesting. As regards fire behavior (rate of spread, flame height, and fireline intensity), significant differences were found 2 years after clearing in a representative heathland in northwest Spain using a wind tunnel simulation experiment [13]. They found reductions of around 60% in the rate of spread and fireline intensity and 35% in flame height-findings which agree with those for FB in our study, but are lower than the values reached at NV or FA.…”

“…As a result, most of them are capable of regenerating easily and are highly resilient to these disturbances in the short term [13,25]. In particular, the rapid response of Erica australis and Calluna vulgaris following disturbance has previously been reported in the Iberian Peninsula [25], these species being capable of recovering their pre-disturbance spatial occupancy and cover values in a short space of time.…”

“…The scarce studies undertaken in shrubland within the Mediterranean area point to an average timespan of approximately 4-5 years for a significant return to pre-harvest fire risk, depending on the type of shrub formation [13,41]. Hence, further research is needed to assess the temporal effects of this treatment on fire behavior in the mid to long term at the study sites.…”

Assessing Climate Change Impacts on Wildfire Exposure in Mediterranean Areas

“…The main strategy to prevent or minimize future wildfire damages in the Mediterranean basin will be the fuel load reduction and forest management by traditional silvicultural techniques or by alternative solutions . This approach requires the identification of major concern areas to prioritize interventions.…”