Abstract:

The mechanisms of tree mortality caused by forest fire are of great guiding significance to forestry practices such as prescribed burning, fire loss assessment and restoration of burned area. However, the action way of forest fire on trees and the factors affecting tree mortality are still unclear. In this review, the forest fire behavior is associated with the burn of tree crown, bole, and roots, and whole-tree mortality. The biological mechanisms underlying fire-caused tree mortality and influencing factors are analyzed. Finally, the review summarizs the method of assessing fire injury and prediction models of tree mortality. It can be seen from the literature review that the direct mortality of trees after fire depends on the burn of leaves and meristem(bud and cambium). The boundary conditions during tissue heating and metric of localized heat-transfer are vital variables in determining and predicting fire-caused tree mortality. Carbon starvation caused by the reduction of canopy photosynthesis and phloem transport and water stress induced by cavitation and deformation of xylem contribute to tree mortality following fire. Compared to carbon starvation, the impact of hydraulic failure on post-fire tree mortality is greater in short term. The response of leaves during fire depends on stomatal conductance and stomatal sensitivity to an increase of vapor pressure deficit, and photosynthesis rate per unit area will increase temporarily due to increasing mineral nutrient after burning. In addition, the variations of secondary metabolites such as phytohormone, phenol, terpene and alcohol, which are correlated with insect attacks, can reflect physiological responses in delayed mortality. Crown scorch variables following fire are reliable to evaluate tree survival and growth condition within short-term. Leaf flushing in the second year following fire can be used as a supplementary standard. For now, independent indicator variables, comprehensive rating indexes and statistical empirical models are the most simple and effective method to predict tree mortality, while biophysical model based on process is further research trend in the future. In addition, this paper also summarizes existing problems in the field, andproposes the corresponding opinions and suggestions in future study related to post-fire tree mortality.

Key words: forest fire, heat transfer, tree mortality, model