基于林火特征分类模型的森林火情等级制图

Forest fire potential forecast based on FCCS model

森林中可燃物的分布状况是影响林火产生、扩散的重要因素之一,本研究的目的是结合森林资源调查数据、激光雷达(light laser detection and ranging,Li DAR)点云数据、地形和气象因子共同驱动的可燃物特征分类系统(fuel characteristic classification system,FCCS)模型来实现森林火险等级预测。以云南省普洱市为研究区,首先,利用机载Li DAR数据生产的树冠高度模型进行面向对象分割,与森林资源二类清查数据叠加分析确定分割单元,并根据可燃物的可燃性将研究区内的可燃物分为针叶林、阔叶林、竹林和灌木林等4种类型,在此基础上采用分层随机抽样形成验证数据集;然后,提取Li DAR变量因子,采用多元逐步回归法反演不同可燃物的森林参数;最后,将森林参数连同气象和地形因子作为FCCS模型的输入,完成各个分割单元的火情等级评价,实现该地区潜在火行为、树冠火、有效可燃物和综合火灾险情的制图。研究结果表明,研究区有效可燃物火险等级比较低,符合研究区的实际情况;森林垂直结构与森林火险等级关系密切,森林参数的准确估测对整个可燃物的制图具有非常重要的作用。

The distribution of combustibles in forest is one of the important factors that affect the occurrence and spread of forest fires.The purpose of this study is to combine the traditional forest survey data with point cloud data from light laser detection and ranging(LiDAR),slope and meteorological factors so as to evaluate forest fire potentials with fuel characteristic classification system(FCCS).Pu’er City of Yunnan Province was selected as the research area in this paper.An object-oriented based segmentation was performed based on the crown height model(CHM)which was produced by the airborne LiDAR data,and the overlay analysis of the provincial level inventory data of forest resources of the research area was used to determine the division unit and vegetation type according to the flammability of vegetation,which was divided into coniferous forest,broad-leaved forest,shrub and bamboo forest.On such a basis,stratified random sampling was used to form the validation dataset.Then the authors extracted the LiDAR variables and applied the multivariate stepwise regression method to analyzing the extracted variables with the reference data set to obtain the forest parameters of different vegetation types.In the end,the forest parameters together with the meteorological factors were used as inputs to the forest fire classification model(FCCS),and the fire potential of each segmentation unit was calculated by the model.Finally,the authors compiled maps of potential fire behavior,crown fire,effective combustibles and comprehensive fire hazard result.The results showed that the overall fire potential level of combustible materials in the research area is relatively low,which is consistent with the actual situation in the study area;the vertical structure of the forest is closely related to the forest fire risk potentials.Accurate estimation of forest parameters plays a very important role in the mapping of combustibles.