Читать книгу Forest Ecology - Dan Binkley - Страница 46

Most forests on Earth have been shaped by fires in the past, and the behavior and impacts of the flames depend on the fuel structure of the forest, on the water content of the fuels, the temperature and humidity of the air, and the speed of the wind. No single one of these factors would be very useful in understanding fires. Many forests experience fires multiple times within the lifespan of dominant trees, including ponderosa pine forests of western North America. Repeated fires lead to ecosystem structures with low densities of trees among small meadows (Figure 2.21). During hot, dry periods, fires may burn readily through the meadows and around the bases of the trees, and a few trees may even have fires reach into their crowns. Strong winds enable fires to race through canopies, but when canopies are very patchy, the necessary wind speeds would be so high that trees would topple over before burning. If fires are absent from such systems for the span of a human lifetime, the forest structure and fuels change so much that surface fires may be less likely, and only moderate wind speeds would be needed to fan flames from tree crown to tree crown. The details of interactions of forest structure, winds, temperature, and humidity would be different for other forests, but the importance of understanding these interactions would be important for all types of forest fires.