Adoption of prescribed burning is increasing as the treatment chosen to decrease fuel hazard in southern Europe but little is known about how it affects wildfire activity. We assessed the effectiveness of prescribed burning treatments by analysing the survival of treatment units to wildfire in mainland Portugal (2005–2017). We examined the time-dependency of treatment-wildfire encounters through survival analysis, and evaluated treatment effectiveness as the intersection outcome in terms of the unburned fraction of the treatment. Generalized linear modelling supplemented by regression tree analysis was used to attain the second objective. Prescribed fire treatments were frequently (42% of the total number of units) intersected by wildfire, which occurs soon after treatment: the probability of an encounter peaked 2 years after treatment and its cumulative value grew at a diminishing rate with fuel age. Of all treated units, 58% burned entirely upon encounter and the median unburned fraction was 0.01 owing to the prevalence of intersections with large and presumably fast spreading and high intensity wildfires. Larger treatments burned less in area but the effect of wildfire characteristics was largely prevalent over the effect of treatment size. The unburned fraction of treated units seldom responded to fuel age, which we discuss based on biophysical influences, treatment effort, and fire suppression strategy. The high encounter rate but low effectiveness in decreasing burned area within treatments and, seemingly, nil effect for practical purposes on wildfire size indicates that prescribed burning is not impacting wildfire extent in Portugal. Our findings indicate the need to scale-up prescribed burning activity to effectively contribute to decrease wildfire size, but also improvements in fire management planning and operations in general.

随着在南欧为减少燃料危害而选择的治疗方法，采用处方燃烧的方法正在增加，但人们对其燃烧对野火活动的影响知之甚少。我们通过分析葡萄牙大陆（2005-2017年）野火的治疗单位生存率，评估了处方燃烧疗法的有效性。我们通过生存分析检查了治疗-野火遭遇的时间依赖性，并根据治疗的未燃烧部分评估了治疗效果作为相交结果。使用广义线性建模并辅以回归树分析来达到第二个目标。规定的防火措施经常（占总数的42％）与野火相交，而野火则在处理后不久发生：在治疗后2年，遭遇机率达到顶峰的时间，其累积值随着燃料使用年限的增加而降低。在所有处理过的单位中，58％遇火时全部燃烧，中位未燃烧分数为0.01，这是由于交叉口普遍存在，且可能是快速蔓延和高强度的野火。较大的处理面积燃烧较少，但野火特征的影响在很大程度上超过了处理尺寸的影响。处理单元的未燃烧部分很少响应燃料寿命，我们根据生物物理影响，处理努力和灭火策略对此进行讨论。接触率高，但在减少治疗中烧伤面积方面效果不佳，而且看似 实际用途对野火大小的零影响表明，规定的燃烧不会影响葡萄牙的野火程度。我们的发现表明，有必要扩大规定的燃烧活动，以有效地减少野火的规模，但总体上还需要改善火灾管理的计划和操作。