Forests are in constant change: new trees growing, old trees dying, flowers blooming, leaves falling. Although barely perceptible to the human eye, these changes happen at a slow but steady rate.
Surprisingly, some of the most important change that happens in a forest is performed by the lowliest element of all—dirt.
Dirt holds the key to the carbon balance in forests, as well as all ecosystems. Carbon is stored in the soil and naturally goes through a cycle in which it eventually returns to the atmosphere. But what happens when the levels of carbon in the atmosphere change, such as in the event of global warming? Can more carbon be stored in the soil? This is what Helga Van Miegroet, a researcher in the USU College of Natural Resources, is trying to find out.
Carbon is a basic element of every ecosystem, and each ecosystem has the ability to store a certain amount of carbon in plants and soils. Van Miegroet has been studying the carbon cycle in conifer and aspen forests to determine their ability to retain carbon in the soil beneath the forest floor. “We have found that the soil beneath aspen forests can retain more carbon than the soil beneath conifers,” said Van Miegroet. “This leads us to ask new questions such as, ‘Is all carbon in soil equally stable, or can some be released into the atmosphere more readily than others?’. We also begin to wonder if there are different types of carbon; if the carbon in aspen forests is different from the carbon in conifers.” All of these questions are part of Van Miegroet’s research to determine how the health of forests affects the carbon cycle in the Intermountain West.
“In nature, vegetation has a tendency to creep, and some colonies will encroach upon other groups of vegetation and even cause them to die out,” said Van Miegroet. She has found that in Intermountain West forests, conifers are encroaching on aspen forests and slightly diminishing the square mileage that aspens cover. “Even the slightest change in these forests can have a major impact on the ecosystem as a whole.” Since aspens store more carbon in the soil than conifers do, Van Miegroet is looking to find out if higher levels of carbon are being released into the atmosphere when aspen trees disappear. This could have a potential impact on carbon dioxide levels in the atmosphere. If a large number of aspen forests were to be lost, the levels of carbon dioxide in the atmosphere could rise significantly.
Van Miegroet is analyzing the effect of conifer encroachment on aspens to determine if and how it could affect CO2 levels in the Intermountain West. Currently, she and her team are taking soil samples at the T. W. Daniel Experimental Forest and Deseret Land and Livestock Ranch, both located in northern Utah. These samples are being tested for their quality and retention of soil organic carbon, which is expressed in terms of chemistry, decomposability, and the amount of water-soluble organic carbon. So far, Van Miegroet and her team have found that vegetation type does affect carbon retention capacity, and could potentially affect future climate projections. As they studied these soil samples from conifers or trees bearing cones and evergreen leaves, aspen, and various forb and shrub sites, they looked at soil respiration, or loss of soil organic carbon, and found that the soils in these systems may vary in sensitivity to climate change. This means that depending on how climate change affects the respiration of soil carbon, levels of carbon in the atmosphere could potentially increase or soil could be a major store for carbon, which could help lower atmospheric carbon levels.
Research conducted in Europe on conifer forests has already shown that climate change is having a big impact on these forests and the surrounding soil. As the climate gets warmer, the tree line in the alpine ecosystems of Europe’s mountains is beginning to rise. The conifer forests are creeping higher in elevation, and since conifer forests hold less carbon in the soil than grassland and dwarf shrub soils, the question is raised whether more carbon is being released into the atmosphere as the conifers creep upslope. Van Miegroet is collaborating with European researchers on this topic to determine whether the same thing might be happening in the Intermountain West as conifers encroach on aspen forests.
In these days when governments are spending millions on green technology research, wouldn’t it be convenient if nature could help solve the problem of excess CO2 levels? As Van Miegroet delves deeper into her research, she is helping create greater understanding about nature’s possible solution to this problem.
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Sidebar: Dirt: The Foundation of Our National Parks