Abstract:

With gradual global warming and drying up, forest fires not only drive changes in the structure and function of forest ecosystems, but also affect the physiology and growth of trees. The thermal damage caused by forest fires can trigger a series of complicated physiological responses in trees. Revealing the response mechanisms of postfire tree physiology can guide the further understanding of the carbon-water relationship and how it influences the postfire growth recovery limitations of trees. Furthermore, the accuracy of tree mortality prediction after fires must be improved. Starting with a description of the pathways in which forest fires affect trees, this review elaborates on the damage caused by different forms of forest fires (canopy, surface, and ground fires) on various parts (crowns, trunks, and roots) of trees. In particular, this review discusses the direct and indirect effects of forest fires on tree physiology and the tree physiology-abiotic/biotic interactions after fires. Cambium and phloem necrosis and xylem hydraulic dysfunction are the main response mechanisms of postfire tree physiology. The two physiological functional limitations—carbon starvation and hydraulic failure—caused by the two aforementioned mechanisms seriously affect the carbon-water relationship of trees, further influencing the growth recovery of trees or their delayed death after fires. The physiological mechanisms of trees after fires are also closely related to drought, insect attack, microbial invasion, and other factors. The quantitative analyses of forest fire intensity and the accurate judgment of the plant tissue death threshold are urgent tasks, and the interaction of tree physiology with the functional traits of trees and other factors after fires must be explored. Accurately evaluating the relationship between tree physiological mechanisms is crucial in fully understanding how forest fires affect the tree functional integrity of trees and contributes to the improvement of forest fire risk assessments and mortality model predictions. In the context of high-frequency and high-intensity forest fires driven by future climate warming and drying, a profound understanding of tree physiological responses can also enhance the study of the dynamics of postfire ecosystems and their interrelationships with climate factors.

Key words: forest fire, cambium necrosis, hydraulic dysfunction, insect attack, microbial infection, delayed death