![[Corel] Seeds survive and reforest the land](2002-03-13-tree.jpg)
Q: How do forests re-grow after they burn? Copyright 2002, all rights reserved
Seeds bring back a burned forest
Q: How do forests re-grow after they burn?
A: A fire turns the soil less acidic and the amount of nutrients available to plants almost always increases. That's why plants burst into verdant re-growth after a fire.
[Corel] Seeds survive and reforest the land
How forests grow back depends on the original forest, the type of fire that raged through it, and what survived the fire. How much tree canopy and organic litter remain influence what grows afterwards.
The tree canopy shades seedlings. Some seedling (like, balsam fir) require much shade, others thrive un-shaded. The seeds of many tree species germinate best in litter-free soils rich with minerals exposed by a cleansing fire.
Almost all fires occur in evergreen forests of pines, spruces, and firs growing in hot, dry country. Fires don't burn everything uniformly. Great green islands-up to 5 % of the total burn-escape unscathed where, perhaps, the ground was wet or the land was downwind of a lake or a bare rock region that protected it from the approaching fire. These patches provide seed for the re-growth.
Red and white pine trees branch high above the ground, well away from a seething surface fire. Moreover, their thick bark can withstand low-level fires. They survive such fires; no re-growth needed.
Cones-the primary rebirth mechanism-safely house the new forest. Even when a lethally hot crown fire kills pine trees, often the dead trees contain mature cones and the seeds survive. Seeds in Jack-pine cones can withstand temperatures of 900° Celsius (1,700 ° Fahrenheit) for short times. Warmth from the fire encourages cones to open, releasing seeds. The seeds spread in the months to come. Within five to ten years, the forest is re-seeded.
White birch and trembling aspen re-sprout from their roots even if badly burned. After a fire-most conifers replace themselves in about 25 years but non-woody leafy plants, lichen, and mosses do not. Instead, they change over the years with variations in shade and nutrients. Grasses and flowers move into open burnt areas and quickly reseed in the warm sun, enjoying the extra nutrients.
"...while coniferous forests burn more frequently, virtually all American forests and other ecosystems have been shaped by fire in the past, including the deciduous forests of the east," says Robert Miller, forestry professor emeritus at the University of Wisconsin at Stevens Point.
In the Midwest, an oak savanna covered the land before settlers arrived. Fires and herds of grazing animals maintained and regenerated the forests. The prairies extended much further east than rain alone would predict because of human and lightning fires. In the Southeast, great forests of southern pines thrived over much of the land before Europeans came and fire maintained these forests, too.
(Answered Jul. 12, 2002)
Further Surfing:
Wildlands League Canada: Forests and fires