Distribution Of Fuel And Potential Fire Behavior Of Typical Plantations In Southern China

This dissertation studied the fuel spatial distribution and characteristics and structure and potential fire behavior in forest space combustible units using fuel classification,fuel loading investigation,statistics analysis,and model prediction et al,through analyses of fuel loading distributions among tree,shrub,grass and litter layer in typical plantations in the Nanning,Guangxi.Based on the analyze of relationship between the fuel spatial distribution and crown fire,combining continuity models of forest fuel,the fuel vertical continuity,horizontal continuity,probability of crown fire occurrence and spread were evaluated,.Precautions to prevent the formation and spread of crown fire have been proposed.The main results are as follows:(1)Pinus massoniana forest has highest fuel loading,Pinus massoniana&Castanopsis fissa mixedforest is in the middle,and Castanopsis fissa forest is lowest;Pinus massoniana forest shrub layer fuel loading is also higher than other two types of forest;thick branches fuel loading in crown has the highest proportion(Pinus massoniana:29.61%,Pinus massoniana&Castanopsis fissa mixed:26.44%,Castanopsis fissa:30.11%),1000h deadwood has lowest proportion(Pinus massoniana:1.80%,Pinus massoniana&Castanopsis fissa mixed:0.28%,Castanopsis fissa:0.17%);flammable fuel loading in Pinus massoniana forestis higher than P&C forest and Castanopsis fissa forest.The flammable fuel is the effectively pyrophorus and closely related to forest fire risk,Pinus massoniana forest potential crown fire risk is higher than Pinus massoniana&Castanopsis fissa mixed forest,and Castanopsis fissa forest is hardly ever occur crown fire.(2)Better prediction of rate of spread(MRE=5.43%)and fire length were obtained by using the surface area weighting method,and better prediction of reaction intensity(MRE=4.07%)and fireline intensity(MRE= 16.29%)were obtained by using the load weighting method.(3)Fire reaction intensity was positively correlated with fuel loading and negatively correlated with moisture content;fire speed rate can be increased by higher fuel loading,wind speed and slope,but when the fuel loading increases to a certain amount,the rate of spread decreased a little instead,Each type of forest certain fuel load amount is respectively 30-32t/hm2.40 t/hm2 and 20 t/hm2;The contribution degree of wind speed is higher than slope,rate of spread in Pinus massoniana forest is higher than Pinus massoniana&Castanopsis fissa mixed forest and Castanopsis fissa forest.(4)Based on environment factors,fuel properties and its spatial distribution,forest burning level were divided into high,medium and low level,fireline intensity,fuel consumption and fire height were of each burning level were calculated.Generally,Pinus massoniana forest has higher energy density in every burning level,and its fuel consumption is also higher when occur crown fire,Castanopsis fissa forest is unable form crown fire,it can only provide optimum surface fire burning conditions within the range of 0?1m,the impact on forest ecological system is minimum.(5)Based on Byram model,fuel vertical continuity(degree)and horizontal continuity(degree)were established according flame combustion state under no-wind and zero-slope conditions.Pinus massoniana forest and Pinus massoniana&Castanopsis fissa mixed forest spatial continuity were evaluated quantitatively by using continuity model.The results showed that Pinus massoniana forest vertical continuity(1.028)and horizontal continuity(3.460)have reached the high level continuity,Pinus massoniana&Castanopsis fissa mixed forest vertical(0.728)is low level continuity and its horizontal continuity(2.083)have reached high level continuity,fuel vertical continuity is key factor to decide whether surface fire convert into crown fire,and horizontal continuity is key factor to decide whether crown fire can be overspread.(6)Fuel continuity loading threshold model was derivate according to flame height level and Byram model,each unit of Pinus massoniana forest Pinus massoniana&Castanopsis fissa mixed forest in 0-3m range fuel loading vertical thresholds were calculated,and then fuel regulation has been made.The optimum regulation plan of different forest type were screened according to reinspection result,so as to compromise multiple objects of forest ecosystem stability maintaining,Timber stands target tree biomass increasing and forest potential fire risk controlling.