Abstract:

A new R-Ⅱequation infered from the heat equation of prerignition int roduced by Rothermel(1972), was given as follows:△Q=H(1-M_f)-4.1816M_f△T_b-2256.68kM_f - 1.599△T_g(1-M_f) where△Q-Net heat value released per kg of fresh fuels; △T_b-Difference between 100 ℃ and atmo-spheric temperature; △T_g-Difference between fuel ignition temperature and atmospheric tempe rature; H-Gross caloric value of fuels; M_f-Moisture content of fuels; k-Ratio of the evaporation capabilty of pure water to that of the water contained in different fuels. Our equation was used to calculate and classify the aloric value by fuels made from 40 kinds of trees and 8 shrubs. The ca lculated net heat values provide an important index for the evaluation of trees resistance to fire. According to the R-Ⅲ equation, the combustion of all woody plants studied can be classified into 3groupe more resistant plants (3590 kJ, 13 spedies), moderately resistant plants(3590 ~ 5822 kJ, 19 species), and poorly resistant plants(> 5822 kJ, 16 species). The species with the lowest combustion values such as Idesia polycarpa, Cratagus pinnatifida, Poqpulus davidiana, Acea davidi, Ligustrum lucidum, Betula luminifera, Populus tomentosa, Juglans regia, Magnolia denudata, Picea wilsoni, Salix matsudana, Plantycaryar strobilacea, Rhus verniciflua, can be selected for use as fire resistant tree plants.

Key words: Tree, Shrub, Combustion, R-Ⅲ equation, Classification