Spatial continuity of fuels in major coniferous forests in Beijing mountainous area: fuel vertical continuity and crown fire occurrence.

This paper researches the fuel vertical distribution quantitatively through the analyses of fuel loads among tree, shrub, grass and litter in major forests (Platycladus orientalis and Pinus tabulaeformis) in the mountainous area of Beijing. The relation between the vertical distribution of fuel and crown fire was quantified by using the vertical continuity indices (C) and ratings. Based on C and ratings, the hazard of crown fire was evaluated and analyzed for two coniferous forests. Results showed that P. orientalis forest(POF) had a high risk of happening crown fires; P.tabulaeformis forst(PTF) had a lower risk of happening crown fires; the fuel continuity of two coniferous forests was evaluated reasonably based on C and ratings, and C of POF was 1.002(high), while PTF was 0.893 (moderate), indicating that the risk of crown fires occurring in POF was higher than PTF. It is also shown that the model can well describe and explain the vertical continuity of forest fuels and the risk of forest fire spreading in vertical direction.