| Forest is the most important part of the ecosystem.Forest fire is one of the important factors that endanger forest resources and destroy ecological balance.Huidong County has rich forest resources,high mountains and dense forests,and the forest coverage rate is in the forefront of Liangshan Prefecture,which is a forest fire-prone area and forest fires have caused great impact on forest resources,ecological environment and social economy.Forest fuels are the material basis for forest fires.Studying the distribution characteristics of forest fuels and classifying the fire risk in forest areas can faciliate fire prevention in Huidong County,thus reducing forest fire risk and occurrence of forest fires,improving the emergency response capacity.This study was conducted in Huidong County.Typical sample plots were selected from Huashan pine,Yunnan pine and alder forests,which accounted for more than 80%of the total forest area in the county.The forest resource data were from the second survey of forest resources and the first inventory of forest resources.Loads of tree,shrub,herb,litter and humus were obtained through the sample plot survey method.The correlation analysis between the forest stand factors,topographic factors and the fuel load of each layer was conducted.Forest fire risk evaluation index system of Huidong County was established by using hierarchical analysis and weighted superposition method.Forest fire risk of Huidong County was achieved by using the spatial modeling function of Arc GIS software according to the weight coefficients and rank values of different factors.The main research results are as follows:(1)The ranking of fuel load across different forests was:Huashan pine>alder>Yunnan pine,with fuel load 97.84 t/hm~2,66.27 t/hm~2,and 80.08 t/hm~2,respectively.The order of the variance of fuel load in each layer of the three forest stands was:shrub layer>humus layer>herb layer>litter layer>tree layer;the order of fuel load in each layer of the understory across the three forest stands was:Humus layer>deciduous layer>shrub layer>herb layer.(2)The total fuel load of Huashan pine forest decreases with the increase of elevation,and the fuel load is most in the range of elevation<2000 m.The total fuel load of Yunnan pine forest and alder forest shows a pattern of increasing and then decreasing with the increase of elevation,and the fuel load is most in the range of elevation 2000m-2500 m.The total fuel load of Huashan pine forest decreases with the decrease of slope,and the fuel load is most in the upper part of the slope.The total fuel load of Yunnan pine forest shows a pattern of decreasing and then increasing with the decrease of slope,and the fuel load is most in the lower part of the slope.The total fuel load in Yunnan pine forest decreased with slope level and then increased,and the total fuel load in the lower part of the slope was the most.The total fuel load in the three stands increased gradually with the increase of densities,i.e.the greater the densities,the more fuel load.(3)Age group,density,elevation,slope aspect,and slope position were the main factors affecting the fuel load of each layer across different forests,but the degree of influence was different.In Huashan pine forest,density was positively correlated with fuel load of tree layer,fuel load of litter layer,fuel load of humus layer,and total fuel load,and negatively correlated with fuel load of herbaceous layer and fuel load of shrub layer.Stand age was positively correlated with fuel load of tree layer,fuel load of litter layer,and total fuel load.In Yunnan pine forest,slope aspect was significantly positively correlated with the fuel load of tree layer;slope position was significantly positively correlated with the fuel load of litter layer.Density was significantly positively correlated with the fuel load of humus layer,fuel load of tree layer and total fuel load;and stand age was significantly positively correlated with the fuel load of tree layer and total fuel load.In both stands,the fuel load of tree layer was negatively correlated with the fuel load of herbaceous layer and fuel load of shrub layer,and positively correlated with the fuel load of litter layer,fuel load of humus layer and total fuel load.Stand age was significantly positively correlated with fuel load of tree layer,fuel load of litter layer and total fuel load in alder stands,while the correlations between other factors and fuel load in each layer were not significant;fuel load in tree layer was significantly positively correlated with fuel load of litter layer and total fuel load,while negatively correlated with fuel load of shrub layer.(4)Through the analysis and assessment of fuel distribution,fuel characteristics and fuel load,we found that Huidong County had a large proportion of forests with high or higher forest fire risk,accounting for 56%of the county’s forest area.High forest fire risk area is 91,422.79 hm~2,accounting for 44.04%of the county’s forest area;and higher forest fire risk area is 24,961.80 hm~2,accounting for 12.02%of the county’s forest area;Medium forest fire risk area is 46123.33 hm~2,accounting for 22.22%of the county’s forest area;Low forest fire risk area is 21941.06 hm~2,accounting for 10.57%of the county’s forest area;Very low forest fire risk area is 687.77 hm~2,accounting for 0.33%of the county’s forest area.High and higher forest fire risk areas are mainly concentrated in Jiangzhou town,Duge town,Yezu street and Jiangxi street. |
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