Abstract: [Objective] Fuel flammability evaluation is one of the most important topics in forest fire research. Different evaluation methods arise due to varied definitions of flammability. One-dimensional methods are commonly used at present. Importance of multidimensional evaluation based on multi-aspects of flammability has already been recognized by researchers but concrete work is not reported. It is not clear whether the two methods are similarity. This study is to identify the differences between one dimensional and three-dimensional method for a better understanding of fuel flammability.[Method] Leaves or needles of seven typical tree species in southern China were used for cone calorimeter analysis. Parameters such as heat release rate and total heat release were obtained. Flammability of the fuels was evaluated for one-dimensional flammability using a principal component ranking method which is commonly used in literatures, and for three-dimensional flammability using heat release parameter recommended by a literature. Spatial distances between the flammability manners were computed for each evaluation methods. The seven species were ranked according to the distances between the two methods. Ranking analysis was conducted on the rankings between the two methods to determine similarity of one-dimensional method and three-dimensional method.[Result] Among the 21 ranking pairs in comparison of two methods for each of the seven species, only two pairs were same in ranking and three with difference of one in ranking, and the rest pairs has large differences in ranking. The ranking correlation coefficients was 0.078, suggesting that the one dimensional method and three-dimensional method would be different and not explicitly connected. Among the ranking analysis of one dimensional ranking and rankings in each of the three dimensions, one dimensional ranking is only remarkably correlated with sustainability but not with ignitibility and combustibility. This indicates that one dimensional method reflects more on sustainability for the seven species.[Conclusion] For the seven species concerned, one dimensional flammability evaluation is significantly different from the three dimensional one, in term of either individual species or all the seven species. Three-dimensional flammability evaluation can reflect more aspects of complicated flammability and providing more information, aiding better understanding fuel flammability and explaining fire behavior while one-dimensional evaluation methods are easy to use. Further work should be conducted to determine better use of the two evaluation of methods.

Key words: cone calorimeter, flammability, three dimensions, one dimension