In Operation Ponderosa, DNA Research for the Big Trees of West Texas
“You can never hear enough sound of wind in the pines,” the writer Gary Snyder says in a poem. It's like a vast breath, enthralling as crashing surf. In West Texas, that sound, and the presence of the towering evergreens, is one of the signature charms of the Chisos, Davis and Guadalupe mountains.
Yet its future is tenuous. A decade ago, between 50 and 75 percent of the big pines in the Davis Mountains were lost – through a combination of historic drought, immense wildfires and bark beetle infestations. Conditions for the trees have always been daunting here, and climate change could push them past the brink. In a century, the West Texas climate may not allow for successful pine regeneration.
Texas conservationists and foresters aren't having it. “Operation Ponderosa” is a partnership between The Nature Conservancy and the Texas A&M Forest Service, focused on pines at the Conservancy's Davis Mountains Preserve. The partners are committed to preserving the big trees in our desert-mountains, and they're using cutting-edge science.
The 33,000-acre Davis Mountains Preserve spans the range's highest reaches, and half its pine habitat – a green world above the desert sea. Operation Ponderosa is centered here.
The partners are protecting existing pines. To reduce the potential for devastating wildfires, forest service and Conservancy crews are removing fuel – by clearing brush and thinning the understory.
But there's a second goal: to regenerate the ponderosa forest by planting new trees.
For this, the partners want local seed – pines adapted to this specific habitat. And that's more complicated than one might expect.
Dr. Fred Raley is a Texas Forest Service tree improvement coordinator.
“In the middle of these three distinct populations of ponderosa in Texas, sits the Davis Mountains Preserve,” Raley said. “So if we want to go local, first of all we have to find out – what does that mean? What is local ponderosa? Is it truly related to the populations more akin to the southern Rockies, or is there some arizonica in the mix? So that's the question I'm trying to answer.”
Raley is spearheading DNA research on the pines.
Because, as it turns out, the status of West Texas pines is a longstanding scientific enigma.
They're customarily identified as ponderosas. Pinus ponderosa, variety scopulorum, is the classic pine of the Rocky Mountains – its bark diamond-shaped, and orange as glowing flame. Yet our trees may in fact be Pinus arizonica, or Arizona pine. It's a species most abundant – despite its name – in the mountains of Mexico. Specifically, analysis of West Texas pines points to Pinus arizonica variety stormiae, which flourishes in Mexico's Sierra Madre Oriental.
In their appearance, the species can be difficult to distinguish – though Arizona pines typically have lacier foliage than ponderosas. West Texas pines could also be hybrids of the two species.
Advances in DNA studies could help resolve the mystery. Raley will gather needle samples from West Texas pines, and the DNA will be analyzed against 50,000 genetic markers. That analysis will allow Raley to compare West Texas pine populations to one another, to assess the genetic diversity within populations, and to determine their relationships with pines elsewhere.
Work in the Guadalupes and Chisos has been delayed by the pandemic. But Conservancy staffers Tara Poloskey and Charlotte Reemts have already done extensive collecting in the Davis Mountains, and in Fort Davis.
“We put together a sampling plan,” Raley said. “We created sample populations that cover eight different elevation ranges, and cover the expanse of the preserve. Tara sampled over 112 trees, and included the trees just outside of the preserve and in town, that we're using as seed trees. So a very comprehensive picture of what that population is going to look like.”
With the DNA findings, Raley will be able to determine the right source of seeds for replanting at the preserve. Seeds from the Guadalupes or Chisos might be used. Typically, trees that are moved from southern to more northerly locales have the best chance of success. As climate change intensifies, hotter, drier conditions are likely to extend northward, and seeds from the Chisos or Davis Mountains might be valuable for replanting in the Guadalupes or southern New Mexico.
The Texas Forest Service has worked for decades with the state's logging industry, helping to sustain and improve the growth and quality of trees – primarily loblolly pines in East Texas. Raley and his colleagues are bringing that expertise to bear in Operation Ponderosa.
They're experimenting with grafting West Texas pines, and ultimately, their objective is to establish a ponderosa seed orchard, for growing saplings that can be planted at the preserve.
“And that seed orchard would be a finite makeup of individuals,” Raley said. “It would be the best individuals put together to meet the purposes of the tree improvement effort, so in this case it would be the 20 most adapted trees for this region, and that's where the seed supply would come from.”
It won't happen overnight. Once a sapling is grafted, it's typically six to eight years before the tree produces a reliable seed supply.
And there are other obstacles. In earlier planting efforts at the preserve, seedlings have been decimated – with hungry gophers the primary culprit. The gophers don't have the same appetite for native regeneration, and physical barriers may be necessary to prevent the predation.
Yet for the forest service, and for the Conservancy, Operation Ponderosa is a long-term commitment, Raley said. The big trees are iconic, and a foundation of biodiversity. Raley is confident that the partners are on a path to preserving these majestic lifeforms of the West Texas mountains.
“When it comes to tree improvement, when you put an objective before you, we can meet that objective,” Raley said. “If it's creating adaptability, if it's utilizing the most of that genetic variation we can to increase the adaptability and survivability of ponderosa pine in the Davis Mountains, and create a seed orchard, so we have sustained seed supply, I think we can meet that goal in the long term, and put our best foot forward in meeting the challenges that might come at us with climate change.”