From the Colorado Springs Independent (J. Adrian Stanley):
Limited conifer regeneration following wildfires in dry ponderosa pine forests of the Colorado Front Range, by Fire Ecologist Monica Rother and CU-Boulder Professor of Geography Thomas Veblen, surveyed conifer regeneration at six low-elevation Front Range sites that burned eight to 15 years before. Released in December and published in the journal Ecosphere, it found that “current patterns of post-fire seedling establishment suggest that vegetation composition and structure may differ notably from historic patterns and that lower density stands and even non-forested communities may persist in some areas of these burns long after the fire[.]”
Translation: Based on historical trends, these sites should have been populated with conifer seedlings. But 83 percent of the sites showed a very low density of seedlings. In fact, 59 percent had no seedlings at all.
Reached at the Florida research station where she now works, Rother says we can expect Front Range burn areas — like our own Waldo and Black Forest Fire scars — to regrow some conifers. But, due to a variety of factors, including increased temperatures, it’s unlikely that the forest will come back the way we remember it. “Our findings show some portions that burn will persist as grasslands,” she says.
Rother says her study can’t pinpoint the exact reason why forests aren’t recovering as expected because there are so many factors involved. Fires that burned hotter leave behind more damaged ground, for instance. Ponderosa seeds don’t travel far, so areas where trees were completely wiped out may be too distant from a seed source. Then there’s temperature, water and elevation to consider. Even the direction the slope faces or the amount of shade provided to an individual seedling can impact survival rate.
But here’s something to keep in mind, Rother says: The older trees that burn in fires were seedlings some 50 or 100 years ago, and we know the climate was different then. The 2014 Climate Change in Colorado report for the Colorado Water Conservation Board, for instance, found that statewide, annual average temperatures have increased 2 degrees Fahrenheit over the past 30 years, and 2.5 degrees over the past 50 years (precipitation levels have meanwhile shown no trend). While that may seem like a small change, Rother notes that in a separate 2015 study published in the Canadian Journal of Forest Research, she, Veblen and research assistant Luke Furman found that when they simulated different conditions that ponderosa pine and Douglas fir seedlings growing in a post-burn Front Range area might experience, those that saw more heat or less water fared poorly.
On a hopeful note, though, Rother says her more recent study looked at portions of three fires on the more northern Front Range, and portions of three more to the south. The southern fires — 2000’s High Meadows Fire, Buffalo Creek, and especially Hayman — showed the best recovery. That might seem odd, given that southern Colorado is known to be dry.
“That was a surprise to us too,” Rother says, explaining that it’s possible that higher altitudes or more summer monsoon rains made the difference on the Hayman.
Jim Gerleman is the Forest Vegetation Program Manager for the Pike and San Isabel National Forests and Cimarron and Comanche National Grasslands — the local guy who’s tracking what’s happening on the Waldo Canyon burn scar. For the past few years, he says, the Forest Service has been planting seedlings over 200 acres in the burn scar.
All the seedlings are grown from local seed and most are professionally planted to target the best possible season (usually April), the most promising slopes, and even the exact sites where the babies are most likely to survive. Over three years, Gerleman says, the trees have had a 60 percent survival rate, which isn’t excellent, but is considered normal.
Ponderosas can be finicky, Gerleman says. They need minerals, which usually means vegetation has to grow first, then die and enrich the soil. But thick grass can also choke out ponderosa seeds.
Waldo, Gerleman says, has come back fairly well — there’s grass, shrubs, even some aspens. But he doesn’t expect the whole forest to regenerate unless they replant it all.
Ekarius says the problem is that ponderosa forests are designed to burn — just not the way that they have. In a natural setting, the oldest trees will survive. A ponderosa mother tree has to be at least 40 years old to produce cones, and her babies grow near her. This is how our forest is supposed to regenerate. But recent fires have burned super-hot, fueled by dry, sweltering weather, and a forest allowed to overgrow due to fire suppression. They left behind a barren landscape.
Ekarius thinks Waldo, aided by wet years, has recovered well. But she expects it to always have areas of grassland where tall stands of conifers once grew. Those grasslands, she says, should prove a good home to elk and bighorn sheep, though they won’t provide suitable habitat to forest squirrels and goshawks. It’s not necessarily a bad thing. “I think it’s different, and I think we don’t like different,” Ekarius explains. “If you’ve been looking at forest for the past 20 years out your back window and now you’re looking at grasslands, you’re probably thinking, ‘Well I didn’t want to live in the plains.'”