Fire in Montana's Bob Marshall Wilderness: Our ecologist blogs from 'the Bob' - Part 3


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The week goes by fast. Before I know it we’ve established and collected data on 20 forest plots and it is time to go home. The week has been spent working hard collecting data, but also talking about big ideas and questions. What role does wilderness play in the era of climate change? What does restoration mean in this new era? One thing is certain. This place has allowed us to reflect on these questions while living and working in a place where nature is left to its own devices. Species and landscapes here are continuing to be shaped by natural forces that have operated for millennia.

It is easy to see that western larch trees tolerate and even thrive with fire. While the hot fires of 2000 and 2003 killed many trees, even some large Douglas-fir, many larch trees persisted through the fire. Their incredibly thick bark and the fact that they lose their needles every year (regardless of fire) allow them to burn but still live to see another season. At the same time, larch like disturbed forest floors created from fires to sprout from seed require a lot of light to grow. In these burned forests, we’ve seen a lot of dead trees, but many huge larch - some over 600 years old – are thriving and many small larch have become established in the understory after the fire. In addition to the many larch saplings regenerating from the forest floor, there are dozens of species of wildflowers and shrubs also thriving after the fire. Pink fireweed and yellow goldenrods carpet the forest floor. In these patchy burned forests, we’ve heard the songs of olive-sided flycatchers all week singing their famous call “quick, three beers!” Olive-sided flycatchers thrive in patchy forests created by fire.

After a week of working in these burned larch forests, a mantra keeps stirring in my head: species matter. Forests are not all alike. A forest’s character including the animals they support, the way they smell and feel, and the way they respond to fire depends on the characters of the species that live there. Western larch is a special tree because it is able to withstand a fire and persist when other trees cannot, ultimately making this type of forest resilient to fire.

From this mantra that species matter, another idea nags me during the week. I’m reminded of maps showing how tree species distributions across the Northern Rocky Mountains may shift under climate change. Western larch is predicted to be a loser in the future because of the forecasted warmer and drier conditions. It is hard to know how long these western larch trees will persist here, but without this tree the forests won’t be the same. Larch trees primarily occur on the west side of the continental divide in Montana, turning forests an emerald green in the spring and a golden yellow in the fall. In forests where larch trees are abundant, their seasonal display of colors arguably rival stands of eastern hardwoods. Without larch, forests would be less resilient to fire, and also less interesting and beautiful. Species matter.

The significance of a forest fire so close to where we are studying the aftermath of similar fires less than 10 years before isn’t lost on anyone. Fires like the one burning near our research site have shaped the forests of the Northern Rockies for millennia. The species that live here show the imprint that fire has written on them. Through adaptations across generations, some woodpeckers have developed black backs – darkened for camouflage against fire-blackened tree trunks. Trees have evolved thick, fire-resistant bark, and some pine cones open and set seeds only into burned forest floors. Some species of beetles actually thrive in a fire’s aftermath and use their own insect version of smoke detectors to find the shelter of burned trees.

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