云南高山林区灌木林火灾蔓延机制研究

There are wide distribution areas of shrubbery forests in Yunnan Province, and several major forest fires trigger by shrub fire each year. The dense shrub forests in central of Yunnan Province are highly dense and concentratively contiguous. If the fires occur at this area, it is too high combustion intensity to directly fight, and easily cause disasters and casualties. The characteristics of understory combustible materials, forest types, and topographic and climatic information will be investigated in shrubbery forest area in central of Yunnan Province, and then the inflammability assessment models of shrubs combustible will be constructed based on flammability index, and the shrubs fuel types will be classified with cluster analysis, and reference to FuelFireTool of combustible parameter characteristics, and results of BEHAVEPLUS software simulation. The main environmental factors of affecting combustibles loads will be determined, then the optimal predictive models will be constructed, and the spatial distribution of surface combustible load will be analyzed. The impacts of human disturbance on forest fire spread and potential fire behavior will be discussed. And the landscape element files will be created with combining small class survey data, surface flammable load capacity distribution maps, DEM data and forest phase maps, then the bush fires will be dynamically simulated with using FARSITE model and selected high fire area as the ignition point, and the spread indicators such as flame length, fireline intensity, rate spread, heat release and spread direction will be selected to fire spread and potential fire behavior. The results will be reduced major forest fires in center of Yunnan Province, and provide scientific theoretical basis to implement forest fire prevention and suppression for the management departments.

云南林区灌木林地分布面积广，每年都会发生几起由灌木林引发的重大森林火灾。滇中密灌区林木密度大，集中连片，一旦发生火灾，燃烧强度大，直接扑救困难，容易酿成大灾和造成伤亡事故。通过调查滇中灌木林区可燃物特征、林分种类、以及地形和气候信息，基于燃烧性指标构建灌木可燃物的易燃性评估模型，选用聚类分析和参考FuelFireTool可燃物参数特征，以及BEHAVEPLUS软件模拟结果划分灌木类型；确定影响可燃物载量主要环境因子并构建最优预测模型，及分析地表可燃物载量空间分布；确定人为干扰对林火蔓延和潜在火行为的影响评价；结合小班调查数据和地表可燃物载量空间分布图，基于DEM数据、林相图建立景观要素文件，利用FARSITE模型、以高火源区为着火点动态模拟滇中林区灌木林火灾的火焰长度、火线强度、蔓延速度、热量释放和蔓延方向等蔓延指标，研究火灾蔓延和潜在火行为空间格局变化，以减少滇中林区的重大森林火灾，为管理部门实施森林火灾预防和扑救提供科学的理论依据。

滇中密灌区林木密度大，集中连片，一旦发生火灾，燃烧强度大，直接扑救困难，容易酿成大灾和造成伤亡事故。基于火灾历史数据及野外调查、室内试验、数值模拟等方法，开展了树种燃烧性评估、可燃物含水率模型和载量模型研建、并分析人为干扰对森林火灾的影响、及灌木林火灾模拟，从微观尺度和景观尺度研究灌木林火的蔓延特征。结果表明：高燃烧性可燃物为过火区10h时滞、枯枝、非过火区活叶、枯叶，低燃烧性为过火区活叶、非过火区10h时滞、活枝。应用ANFIS系统构建过火区、非过火区1h时滞、10h时滞、活叶、活枝可燃物最优模型分别为A01G3、A10T3、AHYG3、AHZG3，B01T3、B10G3、BHYT3、BHZT3，ANFIS系统适用可燃物含水率预测，拟合效果较好。利用逐步回归分析法构建可燃物载量回归模型，其中过火区1h时滞、非过火区10h时滞的模型拟合精度较高。云南省灌木林火灾与气象数据显著相关，高发区为昆明和大理，未来三年呈倍数增长趋势；人为正干扰指标为经济投入，负干扰指标主要为烧荒烧炭和野外吸烟；道路缓冲区Ⅱ区、居民点缓冲区Ⅱ区、水系缓冲区Ⅲ区、GDP缓冲区Ⅰ区为森林火灾重点防控区。基于FDS微观山地模型火灾模拟时帽斗栎林在高风速情况下热释放功率达2.16×104kW，燃烧速率达1.22kg/s，烟气流速达15m/s；柞木林平地燃烧温度达2000℃、烟气热辐射量为1500kW/m3~1700kW/m3、烟气流速为15m/s。FARSITE模拟防火期初期、中期、末期的帽斗栎灌木林火行为特征呈现单位面积燃烧强度Ⅳ级，其他指标Ⅰ级；防火期中期林内飞火点蔓延面积最大，同时林缘火行为等级达最高值，呈现蔓延速度Ⅱ级，其他指标Ⅴ级，灌木林火行为特征受火险期变化影响较小。研究结果可为管理部门林火管理、林火预报、林火扑救提供技术支持，提高林火管理水平，实现林业可持续发展。