| Forest fires have their characteristics such as paroxysmal, stochastic and random, and they have steps from shaping, erupting, and extinguishing. At the same time, forest fire are one of the most difficult natural disasters, it is very dangerous to fight with. When facing special environment, the fires will be random and fastness. The same fires can't exist in the world are due to uncertainty and different losses.During fire, it is necessary to forecast and predict spread rate, energy releasing, fire intensity and degree of difficulty to fight with, in order to match human resource and equipments. Fire behaviors'research is helpful to master forest fire dynamics, prepare for fire occurring, well decision-making and fight effectively and safely. But the processes of research on fire behaviors are slowly because of fire behaviors'complex and experiments'difficulty.After snow and ice disasters, stands of forest and new burned areas in Hunan province were surveyed by setting field plots. Moisture content and fuel load were measured by sampling in order to calculate fire behaviors such as rate of spread et al. The results shown fuel load increased instantly, fuel thickness enhanced, fuel continuity swelled and moisture content decreased due to shrubs and herbs died. Load of fuel variated from 12.23t/hm2 to 50.26t/hm2, five sites exceeded 20t/hm2. With fire environment changing sharply, fire behaviors become complex and bring on fire fighters'fatalness. Fire square and perimeter rates of spread are 111.67～972.71 m2/min and 427～790 m/(24)h respectively, while fire intensity is 675～7 500kw/m, the average exceed 3 500 kw/m, with characteristics of conflagration. These fires consumed over 85 percents fuel, and released huge energy. Fire severity index exceed 85%.Meteorological information were collected from local weather bureau, fire sites and comparing plots in Daxing'anling were surveyed by setting field samples. At he same time, samples in these plots were gathered. Moisture content, fuel load, heat capacity, ignition point and ash content were measured in laboratory. Fire behaviors were analyzed from fire site shapes, combustion depth and ground fire classification. The results showed correlation between combustibility with dryness of fuels and meteorological conditions. In northeastern China, between March and April, even ambient temperatures are below zero and soil freezing, ground fires will occur. The production of Deyeuxia angustifolia meadow is so high that after rotting, decomposing, and depositing, they can easily change into ground fuels. Because of high ash content, it is hard to measure the heat capacity, while ignition points can be obtained. Ignition point of semi-decomposed layer and humus are 405℃and 525℃respectively. Due to thickness, compactness and moisture content, ground fire behaviors are complicated.In view of ecological character, fuel framework, based on forest sub-type and forest fuel characters, by field surveying forest structures and natural conditions, main conifers of Yunnan province can be simplified into 6 types, including Pinus yunnanensis with shrub, Pinus yunnanensis with grasses, Pinus kesiya var. langbianensis with shrub, Pinus kesiya var. langbianensis with grasses, Pinus armandii with shrub and Pinus armandii with grasses.By field surveying and lab experiments, indexes of 6 types of fuel characters including fuel loading, surface area-to-volume ratio, fuel bed depth, dead fuel extinction moisture content, heat of combustion of dead fuel and live fuel can be input BehavePlus model. Using outputs of indexes such as flame length, fireline intensity, heat per unit area, and surface rate of spread (maximum), potential fire behaviors can be evaluated. The results shown that fire behaviors of conifers complex. Fire behaviors of Pinus kesiya var. langbianensis -with shrub are strongest, its flame length, fireline intensity, heat per unit area and surface rate of spread (maximum) is 2～16m, 5 000～12 0000 kw/m, 20 000～27 000 kJ/m2 and 10～270 m/min respectively, while Pinus armandii -with grasses'are least, its flame length, fireline intensity, heat per unit area and surface rate of spread (maximum) is 0.8～4.5 m, 300～6 500 kw/m, 12 000～18 000 kJ/m2 and 1～25 m/min, respectively. The differences are ascribed to natural conditions, ecological habit and fuel characters.By burned sites surveying, fuel experiments, and modify spotting distance, the results shown that cones of Pinus yunnanensis have well structures for spotting, if condition are appropriate, such as weather and topography, they can easily spread. The spotting distance can be estimated from formula. The spotting distance of Anning fire site is between 1.24 km and 3.34 km, inosculate to actual distance. |
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