Study On Combustibility Of Forests In Beijing Mountain Area

Different tree species has different difficult degree of ignition and different reflection on burning and different forest types has different injury degree, also different influence on fire. Therefore, tree species flammability and forest combustibility have always been emphasis on forest fire research.Firstly, flammability evaluation modelings of main tree species and undergrowth plant in Beijing area were presented as functions of heat of combustion submodels using linear regression and principal component analysis, with twenty tree species, eleven species of shrubs and ten species of herbs in Beijing area as object. They were F=17.726H1+25.134H2-808.883 for tree species, F=183.307H-693.687 for shrubs, and F=38.438H-698.264 for herbs. In addition, flammability ranks were divided as flammability indexes≥1.32390,≥1.87345,≥1.45792 for tree species, combustibility indexes-0.41667～1.32389,-0.47890～1.87344,0.24663～1.45791 for shrubs and non-flammability indexes≤-0.41666,≤-0.47899,≤0.24662 for herbs.Secondly, flammability of stand composition(x1)was calculated with flammability evaluation models of main tree species and undergrowth plant, combined with combustibility index of floor dead fuel(x2), load index of gradient flammable fuel(x3), continuity index of flammable fuel(x7), combustibility index of crown flammable fuel(x4) and forest fuel moisture (x5-6) as six sub-indexes. Floor and crown forest combustibility evaluation model were established respectively with principal component analysis, and finally formed to forest combustibility evaluation model. They were Ynf =0.778 x1+0.632 x2+0.283 x3+0.023 x4-0.534 x5-0.091 x6+0.341 x7 in non-fireproof period,Yf =0.025 x1+1.013 x2+0.166x3+0.088 x4-0.448 x5-0.147 x6+0.745 x7 in fireproof period. Also, five combustibility ranks were divided by combustible parameters the models produced. Higher combustibility≥2.9998 and 1.1402～1.4395, high combustibility 1.1382～2.9997 and 0.4918～1.1401, combustibility-0.2567～1.1381 and0.1473～0.4917, low combustibility-1.1215～0.2568 and≤0.1472 in non-fireproof with lower≤1.1216 and in fireproof period with highest≥1.4396 respectively.At last, the combustibility of four forest farms in Beijing area were evaluated with forest combustibility and fuel reduction treatments were discussed with actual situation of forest farm.The results are basic for further study on fire behavior and forest combustibility ranks of Beijing area can provide reference for making of forest management treatments and fire danger evaluation.