June 4, 2010

Yellowstone National Park Part I - The 1988 Fires, Wyoming

From Grand Teton, we entered Yellowstone National Park from the south and headed up to West Yellowstone for the night. The route took us past grassy meadows full of bison, extensive stands of lodgepole pine, and huge burned areas from the famous 1988 fires.

Here some bison sit under the shade of some scorched by still standing lodgepole pines

Despite the devastation of the 1988 fires, the regeneration was well underway. Literally millions of young lodgepole pines burst from the ground following the fires. Lodgepole cones open under intense heat dropping their seeds onto the nutrient-rich ashy soils. The bodies of the parents literally nourish the young seedlings. This cone opening property is a crucial adaption to these fire prone ecosystems.

The burned landscape on the western side of the park

So, here you can see why such catastophic fires can happen in a lodgepole pine ecosystem. The dense growth of these trees provides ample opportunities for the fires to spread across the crowns of the trees, destroying the entire forest. But, what ultimately allows the fire to reach the crown is the growth of younger trees to provide a ladder for flames to reach the top. Lightning is the most common form of ignition.

For the most part, fires create patches that provide an abundance of different ecotypes for plants and animals. Dense older stands that avoided being burned are surrounded by standing dead trees, younger stands, and meadows. Those snags provide habitat for woodpeckers, bats, owls, insects, and all sorts of animals that will be able to spend some of their time in the other patches. Notches in ridges, usually containing streams, greater shade, and additional moisture generally can shelter forests from the less intense fires. Thus, fires are often most intense on south-facing ridgetops and less so in shady hollows.

Fires are crucial to ecosystem health as long as it does not burn all of the trees completely to the ground. These catastrophic fires take many more years to return to maturity and for the patchy mixture of stands to develop. Fire suppression has created unnatural expanses of aging forest full of fuel that allow for catastrophic fires to burn hotter and more extensively than ever before.

Here, you can see an expanse that did not burn in 1988, but probably will burn catastrophically some day in the future.

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