YNP: In Memory of Trees

As we left on vacation, I called my mom, and mentioned we were driving to Yellowstone again.
“But you’ve been there before” she asked.
Yes, many times. We’ve been going every six years or so.
Well, in 1988, you may recall, much of the park burned. The fires were in the news all summer. We’ve been watching the forest grow back.
“It’s been 30 years, love, I’m sure it just looks like forest now.”

My mom has traveled, but her home ecosystem is the farmlands and the white & jack pine forests with oak savannah meadows. An awful lot of the ‘forest’ is paper mill lands growing pines in rows for easy harvest. This is what “normal” looks like to her, and a mature forest is ready to be removed and replanted in 15 years. Of course there are wilder lands, with under brush and more of a mixture of trees, but the difference from the Midwestern highway is slight.

In 1988, the western wildfires hit during a perfect storm. The west was in a major drought. Little rain fell in July, and it was hot, hot, hot. Smokey the Bear was still making his point of fires being unnatural and must be stopped. Human suppression of all fires meant that there was a plethora of twiggy fuel just laying around everywhere. And the normal fire season started, and just kept going. Thousands of wildfire crews and hot shots turned out to combat it, but by the time the cool weather hit in the fall, 63% of the park had burned.


The fires can roughly be divided into

  • ‘Regular wildfire’, in which the undergrowth and lowest dead branches burn, along with downed trees and the occasional live one. Normally, after these fires, fireweed and other post burn plants burst forth.
  • ‘Canopy burn’, where the fire has walked up the ladder of lower dead branches to take the upper treetop, and can quickly spread across the tops in the wind. And did, as the various fires generated their own updrafts.
  • ‘Sterilizing burn’, where the fire was so hot that the ground was cooked.

Note that these are my categories, I’m sure the foresters have more technical terms.

Sterile burn

Baked clay from hot fires

A third of the park was in the devastating sterilizing burn category. Nothing grew where the fires had touched. No fire weed sprung up from the moistened ground in the spring, it was dust over kiln dried clay.

Scott did his first cross country trek to the park in 1987. He wasn’t taking photos then, at least not that survived to today. But he saw the tall mature lodgepole forests and the laughing brook of the Kepler cascades and oh so many bison.

He returned again in 1989. And it was barren, dusty, dirty, dead. The remaining live parts of the park were where the wild things were, and the ashy mud holes were just beginning to get the microbial stew going again. He enjoyed the thermal features, and even with 63% in ash, the park had trails in unburned regions, where the lodgepoles still had their hold.

I joined him in this pilgrimage in 1994. By this point, there was some life. Fireweed is a generic name for a number of plants in different ecosystems, and its the first plant that can process the ashy soil. As it dies back in the winter, its seeds spread in the wind for future burnt bounty, the stalks become mulch for the next year’s growth. I recall meadows of the stuff, purple flowers with yellowing grasses about, growing under branchless black trunks. For acres and acres. Pretty, in a stark way, but you didn’t want to hike through those areas, as the widowmakers were likely to drop at any time.



In the late 90’s, Scott, Doug and I headed out there, and backpacked near Lone Star and Shoshone Lake, which was a mostly unburned portion of the park, and had lodgepole pines consistently 75 feet tall. At the backwoods geyser basin, post eruption, as other tourists began to hike back to the road and we rounded he thermal area to head towards the lake, a woman had given us the hairy eyeball, finally saying “don’t step on that Buffalo” which made us all freeze in place and look around. Tall tree, not a bison. Gravel path, check. Geyserite covered boulder, right. Then the boulder shuddered and turned to look at Doug. We backed away slowly. After a couple overnights in the old growth forest, we returned to the roads and the tiny pines – knee high, for the most part. But they were growing.


Scott & Doug on trail

Lodgepole are serotinous, having two types of pine cones. The average cone opens up in the fall and disperses seeds that become new trees (soil, water, and sun permitting) the next year. These all burned in the hot fires. However, the other type of cone stays shut on a normal year, sealed with resin. If it gets hot enough, they will open up to do post-fire dispersal. So natural reseeding was happening as soon as there was soil to support it.

Indeed, the aspen started moving in. They are sessionary species, which the lodgepole will outcompete, but grow faster than the pine, and therefore got a toehold. When aspen turn color in the fall, the entire grove goes at once, because it’s all really one tree, connected by the roots.

But the winters are harsh in Yellowstone, with wind and deep snow and lots of elk trying to eat leaves and needles when available. Their chewing patterns, after five decades of human managed landscape, had changed to sit still and eat it all, particularly in the riparian zones, wateredge succulents. However, humans being learning monkeys, we’d implemented a couple changes.

The one most relevant to the elk, though they wouldn’t know it yet, was the reintroduction of wolves. Being a prey species again means the elk have to look around more, and move more, which changes where the browse happens.

The most relevant to the ecosystem was the recognition that fire happens, even in a human free wilderness, and it’s a renewing agent of change. Smokey the Bear still wants you to douse your campfire and not toss lit cigarettes out the window, but if a lightning caused fire happens in wild lands, it mostly gets to burn itself out (infrastructure and lives being protected). This means no massive build up of dry fuels on the forest floor, and even when a fire happens, its more the regular fire than the sterilizing version.

So smaller fires happened, and the baby lodgepoles grew. Slowly.

And cone dispersal happened, reseeding areas further into the burns.


Kepler falls after fire

When we returned again in 2005, as part of our Walkabout tour of the continent, the bare patches were all young forest deep enough to hide a standing bison, and the Grant Village museum had been dusting off their “10 years after the fire” exhibit for 6 years. The park had signs at viewpoints describing the wonder of the natural cycle of fire. Most of the widowmakers were down, blown over during winter storms, with the remaining standing dead were bleached white and presiding over the smaller trees.


Kepler 2016

And here we are in 2016. Scott’s camera gear has certainly evolved, shooting RAW on professional digital SLR. We again did a hike out to Shoshone Lake, and strolled beneath the 75ft lodgepole forest, with its mature ecosystem and dappled sunlight. A peregrine swooped down the trail corridor and was very surprised to find us in its route.


Shoshone Lake

But now when we scan across burn to non-burn areas, we see mature trees, and…less mature trees. The burn areas are still obvious.

On a hike near Canyon called Cascade Lakes with Jessica, we noted that the trees are still much shorter, about 15 feet tall, and more cramped together. Not only could a bison hide behind these stands of trees, he’d have a hard time stampeding . Ok, no, nothing shy of a freight train stops a charging bison, but for even a maneuverable human, picking your way through trees that close together is near impossible. Competition is about to thin them out, as they can’t just keep growing like this. I was reminded of the thicket back in the Midwest that grew up after a tornado had devastated the land – trunks inches apart, no understory room for an ecosystem.


Jessica overlooks partial burn from lookout

One later sunset, across the meadow just south of this trail, we saw four wolves skirting the woods, finding it easier to put up with those humans and their binoculars than to shoulder their way through the thicket. When they found a hole in the dense wood, they quickly disappeared.

The aspen are retreating, outcompeted by the stands of lodgepole, which do turn into an interesting monoculture in this climate.



Some areas still have black widowmakers and tiny pines and fireweed beneath them, and I assume those are from more recent burns. My map from ’93 shows the burns in light grey (regular) and dark grey (sterilizing) shading – ideally want to overlay *all* the burns since 1988 and see what parts of the park have thus far been spared, vs which parts have been hit and re hit with fire.

A new map, bought this year to find trail updates, doesn’t mention the fires. The roadside signage is still up if you know where to search for it, and if you head to Grant Village, the museum still has the same “10 years after” exhibit – though, as Mom pointed out, it’s now 30 years after. The forest is still in recovery, though it’s making great progress.

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