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Shared Roots and Survival in the Quaking Aspen

A landscape of quaking aspens up against a mountain range turning yellow for the change of seasons
Aspen trees grow in large groves, like the one pictured above. When one tree is disconnected from the interconnected root system, it can suffer fatal consequences.
Photo by Nathan Jones

Water flows through the soft soil and the aspen trees’ roots soak up every last drop. But the lone aspen cut off from its family’s interconnected root system receives less water, and ultimately, may suffer fatal consequences.

Plant and wildlife sciences student Nathan Jones (‘23) wanted to know why isolated aspens don’t survive. To pursue his passion for the quaking aspen, Jones applied for and received a CURA grant (College Undergraduate Research Award). These grants offer up to $3000 to fund the student’s mentored research experience.

“Aspen trees are, in a lot of areas, a key species. The health of the aspen trees is really indicative of the health of the other animals and plants in the area,” Jones says. Not only do the aspens provide shelter and foodfor plants and animals, the tree creates a microhabitat, protecting developing organisms from harm.

Vegetation depends on the aspens for survival—but one lone aspen couldn’t possibly protect a growing habitat, which is why aspens share a root system. When looking at a forest, one may see several aspens grouped closely together. Those hundreds of trees are actually one organism. This connection not only provides shelter for flora and fauna; these connections are essential in the growth of baby aspens. Jones wanted to learn how much the interconnected root system affects the saplings’ development.

With his mentor, plant and wildlife sciences professor Samuel St Clair, Jones performed the necessary field work and measurement gathering, which involved severing root connections of four different-sized saplings, ranging from as small as fourteen inches tall to nearly ninety inches in height. St Clair and Jones repeated this process with six genetically different aspens to determine whether root-stunted growth was a species-specific phenomenon or an aspen-wide one. Over four seasons, the research team measured the severed saplings' growth, photosynthesis, and survival.

The results stunned them: severing the trees from their roots didn’t prevent them from growing. The integrated baby trees grew similarly to those that separated from the organism. But what caught Jones’ attention was the aspens’ survival rate.

“The ones that were connected were about 25% more likely to survive. So, 100% of the connected trees survive the growing season, while 25% of the disconnected trees died,” Jones says. This happened across all the four size classes and six species.

Why would this happen if the severed trees grew at the same rate as the connected ones? There are several theories, but Jones believes the survival correlates with water sharing. “Maybe one area has more water than another, so they’re able [to use the roots] to shunt some of that extra water over to the trees that don’t have as much,” he says. The aspens separated from the rest of the organism, though, are less lucky. In this case, they would receive less water and have a higher chance of death.

Jones looks forward to continuing experimenting with the aspen. In August and September, he returned to the Provo mountains to study more about the aspens’ chemical composition and leaf size. He hopes to ultimately determine the exact reason why trees separated from their common roots die, and why connected ones live.