Pretty soon, clues hidden in centuries-old tree stumps may help guide restoration work on hundreds of acres of forest near Taos.
Back in 2016, staff with the U.S. Geologic Survey scoured mountainsides in the Río Hondo, Río Pueblo and Río Fernando watersheds looking for evidence of ancient wildfire. The goal was to gather enough data to get a sense of the role wildfire historically played on the Taos landscape before people got too good at putting any fire out.
"The cool thing about trees is that they record the environment," said Ellis Margolis, a research ecologist with the U.S. Geological Survey, on a field trip up Taos Canyon this fall. "Trees record the climate, but they also record fire."
Many people understand that the width of a tree ring indicates whether a particular year was wet or dry, but on certain species, those rings also show scars caused by low-intensity wildfires.
At this particular site, about a mile west of the summit of Palo Flechado Pass, Margolis' team found a weathered old stump that showed the tell-tale wounds of old fires. They cut out a cross section of the stump, and other stumps nearby, and took the samples back to the lab where they polished up the rings and analyzed them under a microscope. By comparing the patterns of wet years and dry years on those trees to a master database, they could pinpoint the age of the tree to the exact year. And fire scars within those rings were also dated to the exact year, and even the specific time of year.
Using this data, Margolis co-authored a study with Lane Johnson that was published by the journal Fire in 2019.
What they found is astonishing. Trees at this site, for instance, recorded wildfires as far back as the year 1500. And on average, low-intensity fires (wildfires that are strong enough to leave a scar but not kill the trees) occurred at this site every 16 years. Samples from similar areas in nearby watersheds showed the same pattern, with some data going as far back as the late 1200s.
But starting in the mid-1800s, humans interrupted those natural patterns. People got very good at stomping out any wildfires in order to protect timber supplies, human infrastructure and livestock. In doing so, we inadvertently created the tinderbox that's causing the catastrophic wildfires that have become increasingly common.
The more mild fires that left scars on the stumps Margolis and his team found played an integral part in keeping the forest healthy for eons. Species like ponderosa pine actually evolved to rely on wildfire to reduce competition for water and nutrients from other trees. A lot of experts these days call that "good fire."
"These ecosystems evolved with fire, burning every 15 to 20 years for centuries," Margolis said. "When you pull that process out, it's like pulling the floods out of the rivers."
According to Margolis' data, the last fire recorded in tree rings at this site was in 1870. And a lot has happened in the century and a half since.
With "good fire" in the mix, smaller trees burned up and ponderosa stands tended to look like a park, with an open understory and large trees spaced far apart from one another. But today, ponderosas around Taos usually find themselves crowded by smaller, weaker trees that become "ladder fuels," carrying wildfire off the ground and into the tree canopy where it burns with much greater intensity. These crown fires often nuke out huge swaths of forests, causing ash flows, erosion and other ecological problems for years.
Crown fires in ponderosa pine are what we call "bad fire." And as the climate warms and droughts become more intense, we're likely to see a lot more "bad fire" creating all sorts of havoc in our area.
For land managers hoping to restore the forests around Taos and make them more resilient to the effects of climate change, the information Margolis and his team compiled is invaluable. Knowing the area's fire history -- the frequency with which fire burned and the scale of those fires -- will help foresters and fire managers come up with ways to mimic the natural cycle for this area.
Six years ago, members of the Taos Valley Watershed Coalition identified the Pueblo Ridge Restoration Project area on the north side of Taos Canyon as a forest that would benefit greatly from thinning work to reduce the density of those small trees and making it safe to reintroduce "good fire" back into the ecosystem. Taos Canyon encompasses the Río Fernando watershed, which is the primary source of drinking and irrigation water for the town of Taos and surrounding communities. Restoring ecological function of the forest and preventing a catastrophic fire in the canyon protects that watershed, not to mention the lives and homes of people who live in the canyon.
On Dec. 1, Pueblo Ridge got the green light to move ahead with thinning, sustainable logging and other restoration work. In the next couple of years, we'll likely see projects on the ground that rely partly on Margolis' data to make these forests healthy and resilient for the future.
J.R. Logan is the Taos County Wildland-Urban Interface Coordinator and manager of several forest restoration projects that promote ecosystem health, traditional uses and economic development in Northern New Mexico. To learn more about the forest restoration and wildfire risk reduction in Taos County, visit taoscountywildfire.org.
