University of Denver Spring 2025

Forecasting the Forests of Tomorrow The Martin Lab is discovering how trees adapt to climate change, one seedling at a time. Mount Blue Sky T r ees are nothing if not resilient. Engelmann spruce and subalpine fir in Colorado’s

“It’s not easy to study because forest dynamics can be measured in centuries,” explains Martin. “And how do you study the whole organism when you’re this big and the tree is 40 meters tall?” Experimenting with seedlings here is fruitful for predicting how climate change will impact forests in the future. Subalpine forests above 10,000 feet like those at the Mount Blue Sky Station have warmed faster than those at lower elevations and have experienced drastic swings in moisture. Light, shade and survival Imagine yourself hiking through heavily wooded forest. While it might be one of Colorado’s signature bluebird days, it can be shady and cool on the forest floor. That’s light exposure—a variable the team studied alongside drought conditions. “We had small gaps where the light is relatively high, and then deeper shade, to see how that interacted with drought stress on the two dominant tree species’ seedlings,” explains Martin. Their findings showed that one season of reduced rainfall disrupts the survival rate of spruce and fir seedlings. However, the silver lining is that shaded areas help reduce drought stress. “They were droughted for two years, but it didn’t just wipe them all out,” says Martin. Their research also had a surprising finding related to the two species, or what Martin calls “species-specific stories.” Spruce prefer sunnier spots, so in the shade, their regeneration has less of a chance to succeed compared to fir. The divergence suggests that the forests of today might look different in the future. “We expect spruce and fir to coexist intimately,” Martin notes, “but you could see drought pushing them in slightly different, more homogenous clusters down the road.” The findings highlight the importance of considering light and moisture conditions when managing forests to ensure seedlings have the right environment to survive. This could have implications for how humans manage forests to adapt in the face of climate change. “We’re not going to avoid it altogether,” says Martin, “but a forest manager could take the research and notice spruce is starting to disappear and clear some understory to encourage regeneration.”

mountains age well into their hundreds, but to reach the sky, they must survive what are like awkward middle school years as seedlings. This precarious stage is what Patrick H. Martin, biologist and professor in the College of Natural Sciences and Mathematics, and his lab of graduate and undergraduate researchers are most interested in as the West faces prolonged and severe periods of drought. “Trees can withstand a lot, but these tiny seedlings are often the canary in the coal mine for how things are changing,” says Martin. Fortunately, the University of Denver’s Mount Blue Sky Station—in operation since 1937—is the perfect natural petri dish for a seedling study. The area’s geomorphology is special due to its alpine glaciers formed during the Pleistocene Epoch—popularly known as the Ice Age—that lasted from 2.5 million to 11,700 years ago. Nearby Echo Lake, for instance, was created by a glacier. “It’s one of the best parts of Colorado to see traces of how the glacier shaped the surficial geology,” says Martin. “Also being a 14er, it’s a little island of high elevation and one of the largest continuous areas of alpine ecosystem in the Rockies.” Typically, researchers might drive thousands of miles to reach such an area, but for Martin, it’s just an hour’s drive from his office on campus, a bonus when he accepted the job. But that doesn’t mean the research is a piece of cake.

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UNIVERSITY OF DENVER MAGAZINE | SPRING 2025