In addition to the extreme drought-conditions, low precipitation and high temperatures, there were other factors making Yellowstone prime for fires in 1988. The park's deeply glaciated, high elevation mountains, which give way to flat plateaus and broad valleys are covered with lodgepole pine forests and crossed by hardly a road. The Lodgepole pine tree, which makes up about 80 percent of Yellowstone's forests is very flammable. With its thin bark and tall growth, it is very prone to fires. The Lodgepole produces two types of cones, open and serotinous.
Open cones shed seed when the cone reaches maturity.
Serotinous cones, on the other hand, are sealed closed by a resin coating which requires temperatures of at least 113 degrees before they will open. Such temperatures wouldn't occur if it weren't for fire. These cones remain on the tree, unopened for years and provide an abundant seed source that scatter over the ground within days of the passage of a fire. If fires are common in a region, there tends to be a higher number of serotinous cones than open. On the other hand, if fires are rare, there tend to be more open cones.