“Creative destruction” has become a dubious cliché in the economic realm. But there’s no gainsaying its role in nature. Wildfire is a prime example. Forests need periodic fire – for recycling nutrients, reducing pests and pathogens and clearing the way for new life.
And then there are “obligate seeders” – plants that require fire to reproduce. Scientist Badri Ghimire is studying one such plant – the Arizona cypress. His findings could impact the future of this lovely desert-mountain tree.
“As of now, I don't think they are species of concern,” Ghimire said. “But they are a species of concern to me personally, since their population is limited to isolated geographic locations.”
Ghimire is a self-described “pyromaniac.” He traces that obsession to his youth in a remote village in Nepal – where fire is central to religious life, and daily survival. Now, as a Texas Tech PhD student, he’s studying fire-plant interactions.
Arizona cypress can grow 80 feet high, with gray-green to blue-green foliage. As Ghimire noted, they’re found in isolated patches in the sky-island mountains of northern Mexico and the Southwest. That includes Boot Canyon in Big Bend’s Chisos Mountains.
“In Boot Canyon – it's a perfect location for them,” Ghimire said, “and they're doing amazing out there.”
Arizona cypress are conifers – but their cones are unique. They’re globe-shaped and “serotinous,” meaning they’re sealed shut with a resinous bond. When fire strikes, that bond gives way – only then can the cone release its seeds.
A century ago, it became U.S. policy to extinguish every forest fire as quickly as possible. That policy led to an accumulation of fuels, contributing to the catastrophic fires we see today. And for Arizona cypress, it meant the end of reproduction.
Nature, of course, bats last, and fire has returned to Southwestern forests. But amidst climate change, wildfire frequency and intensity have increased. Historically, Arizona cypress stands were destroyed in fires. But their seeds endured, to germinate in the ashy, nutrient-rich soil. Fiercer blazes threaten that cycle.
“They are obligate seeders,” Ghimire said, “but they do not prefer fire with higher severity and intensity. Too high-intensity fire would kill the entire seed.”
And with increasing fire frequency, new trees can be killed before they reach maturity and develop cones.
Ghimire has collected cones from Boot Canyon, and from sites in New Mexico and Arizona. In the lab, he’s subjecting those cones to fire, in what he calls his “plant barbecue machine.” He’s hoping to determine the “sweet spot” – the fire intensity at which cones opens, and seeds survive.
Land managers now appreciate fire’s role in forest ecosystems, and conduct controlled or prescribed burns across the Southwest. Ghimire’s findings could help them introduce fire in ways that support Arizona cypress.
Ghimire is also studying Arizona cypress genetics. It’s likely the trees retreated to their mountain sanctuaries since the Ice Age, and were once more widespread. Genetic analysis could show if the populations have become distinct species.
For now, the Big Bend Arizona cypress appear to thriving. That’s also the case in Arizona’s Chiricahua Mountains. But in the Tonto National Forest near Phoenix, Ghimire said, increased fire frequency may be driving the trees to the brink.
Ghimire hopes his work can help save the trees.
“These are an understudied plant,” he said, “and there's a big knowledge gap about their ecology, their evolutionary adaptation to this landscape. Hopefully our effort is good enough to maintain their population, and I hope my research can contribute.”
The Chisos and other desert mountains are rugged landscapes. But their ecosystems are fragile. Preserving their distinctive inhabitants will take care, and study.
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