Study On The Mechanism Of Surface Fire And Spread Of Canopy Fire Of Typical Tree Species In Beijing Area

This paper takes typical tree species in Beijing as the research object,and studies the mechanism of surface fire spread and the spread of surface fire from the bottom to the top of the tree for Pinus tabulaeformis,Platycladus orientalis,Quercus mongolica,Robinia pseudoacacia,Quercus variabilis and Poplar.Methods The field survey,internal experiment and software analysis were used.The main models used were Rothermel model and Van Wagner model.The objectives of the study include:(1)surface fire spread:surface fire spread speed,unit area,heat of surface fire,fire intensity of surface fire and flame height of surface fire;(2)spread of surface fire to canopy fire Part:mainly combined with the fire intensity of surface fire,the average first branch height of each forest and the absolute moisture content of each year,simulating the potential surface fire and canopy fire behavior in Beijing.The significance of the study is to provide a reference for the potential fire behavior of forests in Beijing and also provide effective data for fire prevention.The main conclusions are as follows:(1)In terms of surface fire,the spreading speed is inversely proportional to the moisture content of combustibles,and is proportional to the near-surface wind speed;the calorific value per unit area is only related to the properties of combustibles,and the moisture content of combustibles is The calorific value produced by combustion has an effect,and the speed of the wind speed does not affect it;the intensity of the surface fire is inversely proportional to the moisture content of the combustible,and is proportional to the wind speed.The height of the flame increases with the increase of the wind speed,and decreases with the increase of the moisture content of the surface combustibles.(2)In the aspect of the fire caused by the surface fire,the absolute height of the first branch of the tree and the absolute moisture content of the tree are obtained.The occurrence of canopy fire has an important influence.The higher the height of the first branch,the greater the absolute water content of the tree,the more likely the tree crown fire will occur;(3)the canopy fire is more difficult to occur in the hedgehog forest,and the mongolian oak forest and the cork oak forest are easier.From the surface fire caused by the canopy fire,the hedgehog can be used as the main fire tree species...