People usually think of Engelmann spruce as only living high in the mountains. So as the climate crisis heats up, the assumption is that such trees may dwindle or die out as they’re forced to move up to cooler temps. But University of Wyoming botany professor Daniel Laughlin said that, after looking at data collected in arboretums across the U.S., he discovered that wasn’t so.
“We see [Engelmann spruce] growing here in Laramie. It could potentially grow in the valleys here along streams,” he said. “But probably why we don't see it is because species like cottonwoods, for example, or maybe even some of the faster growing pines, out compete that species and sort of pushed Engelmann spruce up to the top of the mountains.”
Laughlin said he found that trees often only grow in about 25 percent of their actual thermal niche. He said, there was another big surprise, as well.
“When we compared all of the potential niches, we saw that almost all species overlapped at a single moderate temperature of about 12 degrees Celsius, which is about 55 degrees Fahrenheit, [the] mean annual temperature,” he said. “This was quite surprising because we see species growing either typically in cold environments or warm environments or somewhere in the middle, but the fact that they overlap at the same temperature was a bit surprising.”
Laughlin looked at 188 North American species, 23 native to Wyoming. He found they likely choose more narrow ranges due to competition and predation with other trees. But really, trees are used to the many fluctuations of the earth’s climate.
“These trees have been marching across the continent for the last 40 to 50 million years, some of them,” Laughlin said. “You think about it and they're not doing it physically, as individuals – they're doing it as populations. Their seeds are traveling far distances and understanding these dispersal rates is really part of the puzzle. The Paleo record is absolutely clear that trees have been on the move and that they're quite fast in their dispersal, especially these long-distance dispersal events that are likely triggered by
relationships with birds that are moving seeds around these far distances, especially things like Clark's nutcracker for example with pine trees up at high elevation.”
He said this research doesn’t mean that we can be complacent about our efforts to conserve wild landscapes though. Going forward, he plans to continue this study to find out how flexible trees are to changes in precipitation and other factors as well.
