基于火模拟的森林火灾风险定量评估——以中国林业科学研究院亚热带林业实验中心为例

Quantitative assessment for forest fire risk based on fire simulation:taking the Subtropical Forest Experimental Center of Chinese Academy of Forestry as an example

【目的】森林火灾风险评估是利用定量或定性的方法综合考虑一个区域的火发生可能性及对环境造成的潜在影响,识别区域内的高火灾风险区是开展科学林火管理的基础。本研究基于森林燃烧概率、潜在火行为和暴露性综合评估一个区域的森林火灾风险,为林火管理部门开展林火管理和可燃物处理提供指导。【方法】利用燃烧概率模型(Burn-P3)在景观尺度上模拟亚热带林业实验中心所属林区的燃烧概率、潜在火强度、蔓延速度及火发生类型。根据火对周围城镇和水源的潜在环境和安全问题计算火灾暴露性。综合这些指标利用层次分析方法定量评估森林火灾风险,分析火灾风险的空间特征和不同类型植被的燃烧性差异。【结果】火模拟结果表明:研究区的平均燃烧概率为0.0401,燃烧概率高和很高的区域分别占研究区的5.3%和2.3%。火烧以地表火和间歇性树冠火为主,平均火强度及蔓延速度分别为2043.6 kW/m2和2.5 m/min。火行为指数高和很高的区域分别占17.3%和6.2%。针阔混交林的燃烧概率和潜在火行为指数最高,阔叶林的燃烧概率及潜在火行为指数最低,但其暴露性指数最高。火灾风险综合评估结果表明,风险高和很高的区域分别占19.7%和6.5%,针阔混交林的火灾风险指数高于其他植被类型。【结论】研究区内大部分区域的燃烧概率较低,但潜在火行为指数较高。城镇和水源附近森林的火灾风险等级高,是林火管理的重点区域。部分针叶林和针阔混交林存在发生稳进树冠火的可能,可以通过可燃物处理措施来减少可燃物梯及地表易燃可燃物,降低火灾风险。

[Objective]Forest fire risk assessment is to describe the potential occurrence of forest fire and the direct or indirect fire impacts on environment at the landscape scale by qualitative and/or quantitative indicators.Identifying the areas with high fire risk is the base of forest fire management.Comprehensive assessment on forest fire risk for a region based on burn probability,potential fire behavior,and exposure provides a guide for local fire agency to carry out fire and fuel management.[Method]We simulated the burn probability,potential fire intensity,spreading speed,and fire types on the landscape scale for the forests in the Subtropical Forestry Experimental Center by the burn probability model(Burn-P3).The potential fire impacts on surrounding communities and water sources were analyzed for exposure.We also analyzed the spatial characteristics of fire risk,burn probability,and potential fire behavior of every vegetation type.A comprehensive assessment model on fire risk was constructed by analytic hierarchy process.[Result]The fire simulation results showed that the average burn probability of the study area was 0.0401,and the areas with high and very high burn probability accounted for 5.3%and 2.3%,respectively.The fire types were mainly surface fire and intermittent crown fire.The average fire intensity and spread speed were 2043.6 kW/m2 and 2.5 m/min,respectively.The areas with high and very high fire behavior index accounted for 17.3%and 6.2%of the total areas,respectively.The coniferous and broadleaved mixed forest had the highest rating on burn probability and potential fire behavior index.The broadleaved forest had the lowest grade on burn probability and fire behavior index,but showed the highest exposure.The comprehensive assessment results on fire risk showed that the areas with high and very high risk accounted for 19.7%and 6.5%,respectively.The fire risk of coniferous and broadleaved mixed forest was higher than that of the other vegetation types.[Conclusion]Most of the study area has low burn probability and high potential fire behavior index.The forests near towns and water sources show high fire risks,which should be the key areas for fire management in the future.It is necessary to carry out fuel cleaning measures to reduce fuel ladder and surface inflammable fuels in coniferous forest and coniferous and broadleaved mixed forest in order to reduce their fire risk.