Short-term effects of prescribed fire for Eucalyptus globulus Labill. slash management in Portugal

Abstract Effective fuel management is a priority in Mediterranean Eucalyptus globulus plantations due to wildfire risk, but the short-term ecological effects of prescribed fire remain unclear. We hypothesized that PF would reduce post-harvest fuel loads without negatively affecting short-term soil properties or stump resprouting in E. globulus plantations. The main objectives were to determine the short-term effectiveness of PF in reducing fuel load and to evaluate its impacts on soil properties and on stump survival and resprouting height. A field experiment was carried out in two recently harvested blue gum stands under contrasting climates in northern and central Portugal during January 2023. Each site was divided into two plots (approximately 0.5 ha each): one prescribed fire treatment and one control, with three parallel transects per plot. Fuel loads, soil properties and stump resprouting were assessed pre-PF and 45–60 d after PF. Soil impacts were evaluated using temperature recordings at 0–2 cm depth and visual soil burn severity. Stump resprouting heights were measured post-fire in both regions. Statistical analyses were used to assess differences between treatments. PF significantly reduced fine fuel loads by 73.5% in Póvoa de Varzim and 60.3% in Nisa compared to the control ( p < 0.05). Soil burn severity was low, with peak temperatures of 117.5 °C and 107.5 °C at a 2-cm depth in Póvoa de Varzim and Nisa, respectively. PF increased soil pH (from 4.0 to 5.0 in Póvoa and 5.7 to 7.1 in Nisa) and phosphorus content. Organic matter levels were unaffected in Nisa and slightly reduced in Póvoa. Stump survival rates were high (> 87%) in both sites, with PF showing no statistically significant difference from control. However, while similar in Póvoa (0.37 m), resprouting heights in Nisa were lower in PF plots (0.50 m) than in controls (0.91 m). Overall, this study provides field evidence that PF can be used to effectively reduce fire hazard without significant negative effects on soil chemical properties or on the short-term survival and sprouting of E. globulus stumps.