Loading Capacity Of Fuels Of Ground Cover And Fire Behavior Of Forest In Changbai Mountain

There was no serious forest fire in the Changbai mountain forest region for 29 years and the general incidence of fires declined. This region belongs to an uninflammable virgin forest. With the extension of the years that there is no large fire happened and the accumulation of understory fuel loads, the fire risk in the region of Changbai mountain increased yearly under the effect of dry climate condition in a long time. The dynamic of forest fuel loads was analyzed in this paper combined with climatic conditions in Changbai Mountain forest region. Base on the partition method of U.S. Fire Behavior Fuel Model, the Rothermel model was used to evaluate the behavior fuel model in Changbai mountain forest regions. The results can provide the possibility to predict forest fires in Changbai Mountain forest accurately, increase the predictability of forest fires and lay a theoretical foundation for establishing the prevention programs, preventive measures and fire-fighting measures of forest fires reasonably. The main research results as follows:The temporal dynamics of input on fuel show that the input of broadleaf, needles and branchless in Secondary Populus davidiana-Betula platyphylla forests, Secondary conifer and broadleaved mixed forest and the original broad-leaved Korean pine forest were mainly concentrated in September and October, reached the peak in late September to mid-October. The order of input on fuel of different type in these forest stands were that the broadleaf > needles > branchless. The total input of broadleaf, needles and branchless in 2006 and 2007 were that Original broad-leaved Korean pine forest > Secondary conifer and broadleaved mixed forest > Secondary Populus davidiana-Betula platyphylla forests. The total input (including broadleaf, needles and branchless) of differential forest types in the year of 2006 and 2007 were that the original broad-leaved Korean pine forest > Secondary conifer and broadleaved mixed forest =Secondary Populus davidiana-Betula platyphylla forests. The total input of fuel in a 5.2ha dynamic forest plots in Secondary conifer and broadleaved mixed forest show an obvious spatial heterogeneity. The content of ash content, crude fat content, heat value were in the same order that Secondary Populus davidiana-Betula platyphylla forests > Original broad-leaved Korean pine forest > Secondary conifer and broadleaved mixed forest.Base on the partition method of American fire behavior fuel model, we established the behavior fuel model in Changbai mountain forest regions. The results of fire fuel model displayed that the spread rate of forest fire and the heat per unit fire area in different stands of Changbai mountain were decrease with the increment of humidity; In the condition of low and middle humidity, the average wind speed of maximum flame in different stands were greater than 8m/s; In the high humidity, the average wind speed of maximum flame in the plot 2 of Betula ermanii forest and the plot 3 of Betula platyphlla forest were 7.11m/s and 7.35m/s separately , the average wind speed of maximum flame in other forest types are greater than 8m/s. In any situations of low, middle and high humidity, the spread rate after forest fire happened in near-mature stand of Betula platyphlla forest is the fastest and the lowest one is in near-mature stand of Larix olgensis forest; The heat per unit fire area in mid-age stand of Abies-Picea forest and mixed forest of Abies-Picea forest and Pinus koraiensis forest are the greatest, while the smallest one is in mature stand of Betula ermanii forest. According to the character of fire behavior in different stands under the low, middle and humidity condition, 13 forest types were finally divided into 8 classes.The analysis of potential forest fire behavior of 8 types of fuel and 13 fuel models show that in addition to mature stand of Betula ermanii forest, the spread rates of fire accelerated with increment of the average flame speed. The spread rates of fire were influenced by the forest fuel humidity, which were low humidity >middle humidity >high humidity in order. Within 0～8 m/s average wind speed of flame, the heat per fire area and maximum reliable wind speed were both keep constant. They were influenced by the forest fuel humidity, the order of which were low humidity >middle humidity >high humidity. The flame length and fire intensity of 8 forest types were also increased with the acceleration of the average flame speed. The spread rates of fire in mature stand of Betula platyphlla forest were greatest, followed by young stand of Betula platyphlla forest and near-mature stand of Larix olgensis forest. Their heats from per fire area were much lower and fire intensity was small, which was suitable to take fire direct extinguishing. The spread rates of fire in mid-age stand of Betula platyphlla forest and the mature stnad of Larix olgensis forest were the smallest, followed by mid-age stand of Abies-Picea forest and mixed forest of Pinus koriensis and Abies-Picea.The heats of per fire area from these types were higher and the fire intensity was greater, which was adopted to take fire indirect extinguishing.