Study On The Fuel Load Of Different Terrain Pinus Tabulaeformis Forests And Their Potential Fire Behavior In The Songshan,Beijing

The main research object of this paper is Pinus tabulaeformis forest which grows under different terrain conditions in Songshan Nature Reserve.Thirty-four typical Pinus tabulaeformis forest samples were set up according to different elevations,slopes and aspects of Pinus tabulaeformis.The spatial distribution of surface combustibles and canopy combustibles of Pinus tabulaeformis forest were analyzed by field investigation(Standard terrain factor and herbs,shrubs,litter,crown combustible load)and laboratory(Calorific value,surface area volume ratio and so on).Combining with Rothermel forest fire spreading model,the latent fire behavior of Pinus tabulaeformis forest in Songshan was calculated by using BhavePlus software of U.S.Forest Service,which will explore the behavior of surface fire and the probability of transformation to canopy fire in Songshan.The results of this research can provide a scientific basis for combustible management and fire fighting and extinguishing work of Pinus tabulaeformis forest.The main results for this study are as follows:(1)The differences of the surface fuel loadings among different altitudes,slopes and aspects of Pinus tabulaeformis forest were significant,and the influencing factors of various types of combustibles were related to elevations and slopes,but the aspects only affected the herbaceous loadings.The sequence of the surface charge of the three terrain loess forest is:H3(1000-1100m)>H 1(800-30 m)>H2(900-1000m);S2(20-30°)>S3(30-40°)>S1(10-20°);A2(southwest slope)>A1(southeast slope)>A3(northwest slope).(2)The total density of the vertical combustible of Pinus tabulaeformis in different terrains has a significant difference,and the vertical combustibles are divided into 0-1.5m,1.5-3m,3-4m,4-5m,5-10m,10-15m,15-20m.There were significant differences in the densities of the combustibles between the seven layers,which are diverse in elevations and the slopes.The sequence of the total density of the vertical combustible of Pinus tabulaeformis in different terrains is:H3(1000-1100 m)>H2(900-1000 m)>H1(800-900 m);S3(30-40°)>S2(20-30°)>S1(10-20°);A3(northwest slope)>A1(southeast slope)>A2(southwest slope).(3)The humidity of the same combustible,the speed of forest fire speeding,the intensity of fire and the flame length are increased with the increase of wind speed,while the reaction intensity is kept constant.The same flame wind speed,the spread speed,fire intensity,flame length and the intensity of reaction of Pinus tabulaeformis forest are decreased with the increase of the humidity of combustible Under the same burning conditions,as to different elevations of Pinus tabulaeformis forest,the size order of forest fire spreading speed is:H2(900-1000m>H3(1000-1100m)>H1(800-900m).Fire intensity are increased with altitudes,the flame length are increased with altitudes.The order of the intensity of reaction is H1(800-900m)>H3(1000-1100m)>H2(900-1000m),the forest fire is a kind of low-intensity surface fire.Compared with different slopes of forest fire behavior,forest fire spreading speed is increased with the increase of the slopes.The size order of such three indexes(intensity of fire,flame length and intensity of reaction)is:S2(20-30°)>S3(30 to 40°)>S1(10-20°).The forest fire can be turned from low-intensity surface fire to moderate-intensity surface fire.Results,Compared with different aspects of pinus tabulaeformis forest,the results are all:A2(southwest slope)>A1(southeast slope>)A3(northwest slope),different aspects of pinus tabulaeformis forest can be turned from low-intensity surface fire to moderate-intensity surface fire(4)The critical value of forest fire intensity is higher in each terrain,and the maximum fire intensity is relatively small.The conversion rate of crown canopy of different terrain pine forest is less than 1.00.Therefore,in the 0-15m/s flame wind speed range,it is difficult to occur crown fire,only the surface fire.And the crowns of Pinus tabulaeformis are poor in the vertical direction,the flame length of the surface fire is below 0.5m,and the flame is difficult to spread to the canopy.