Research On Moisture Content Of Dead Forest Fuel And Fire Danger Rating Of Major Tree Species In Anning Area

Anning area has abundant forest resources and it is also a forest fire zone.How to accurately predict the moisture content of forest surface dead combustibles and improve the accuracy of forest fire forecasting is of great significance in promoting forest fire protection.This study was conducted to analyze the relationship between the equilibrium moisture content(EMC)time-lag of combustibles and temperature?humidity by taking surface dead fuels of Pinus yunnanensis?Cyclobalanopsis glaucoides Schotky,Eucalyptus maidenii and Alnusnepalensis as examples.The optimal EMC model was selected to analyze the suitability of Simard model?Nelson model?Van Wagner model and Anderson model.Surface dead fuel moisture models were established by studying the trend of change in the moisture content of fuels from March 16 to March 26,2017.The results are as follows:(1)Under the same temperature conditions,EMC and time-lag of the litter and d leaves increased with increasing humidity and decreased with increasing temperature.That is to say,EMC and the time-lag of litter and leaves were positively correlated with humidity,and negatively correlated with temperature.(2)The Simard model and the Neslon model fit best with the experimental data among the four EMC models.The error distribution is concentrated within 3%,which can be used as the EMC response function in the prediction model of fuel moisture content.However,the error distribution of the Van Wagner model and Anderson model were relatively large,the stability and applicability are poor.(3)There is a strong heterogeneity in the moisture content of fuels.The difference in the moisture content of fuels between Pinus yunnanensis and other three tree species is extremely significant(P<0.01);The differences between Alnusnepalensis,Cyclobalanopsis glaucoides and Alnusnepalensis were significant(P<0.05).The water content of leaves was significantly different from that of dead branches(P<0.01).There were significant differences between litters at 1 hr and 10 hr(P<0.05),and the difference was significant between 100 hr and leaves(P<0.01).(4)The accuracy of the model of the water content of fuels using the direct estimation method is relatively high.The average relative error and the average absolute error are less than 10%.It can meet the accuracy requirements of the forest fire forecast on the prediction of the combustible moisture content and can be achieved in hours.The prediction of the moisture content of the fuels provides effective help for the forest fire prevention work.(5)Based on the critical moisture content,fire risk can be divided into 5 levels with 32%,25%,17%and 10%as the boundary points.When the moisture content of fuels was less than 25%,the degree of fire hazard is more than moderate,and fire patrols need to be strengthened to prohibit all wildfires.