Warming Climate May Cause Arctic Tundra To Burn

[phantom power]

By looking at fossilized pollen grains in the sediment cores, Higuera and his co-authors determined that after the last ice age, the arctic tundra was very different from what it is now. Instead of being covered with grasses, herbs, and short shrubs, it was covered with vast expanses of tall birch shrubs.

Charcoal preserved in the sediment cores also showed evidence that those shrub expanses burned -- frequently.

"This was a surprise," Higuera said. "Modern tundra burns so infrequently that we don't really have a good idea of how often tundra can burn. Best estimates for the most flammable tundra regions are that it burns once every 250-plus years."

The ancient sediment cores showed the shrub tundra burned as frequently as modern boreal forests in Alaska -- every 140 years on average, but with some fires spaced only 30 years apart.

http://www.sciencedaily.com/releases/2008/03/080304100413.htm