A University of Wyoming study in Yellowstone National Park is providing scientists with a glimpse at how increased carbon dioxide might affect plants and animals 100 years in the future.

Researchers Shikha Sharma and David Williams have sampled leaves from lodge pole pines, the dominant tree species in the park, and Dalmatian toadflax, an invasive species, to see how increased carbon levels affect their growth and metabolism.

The study is closely related to Yellowstone’s geology; the park’s vents spew large amounts of carbon into the atmosphere. Plants near these vents are subject to almost twice the amount of carbon dioxide – about 600 parts per million – as plants in a normal atmosphere where CO2 levels stay at around 380 parts per million. The earth’s atmosphere is expected to contain about 600 parts per million of carbon dioxide in the next hundred years if humans keep relying so heavily on fossil fuels.

“The conditions near these vents replicate what scientists think will happen to the planet over the next century because of man-made sources of carbon dioxide,” said Williams. “We have the opportunity to see how plants are growing across a range of CO2 concentrations around the vents.”



Plants near vents do change

The scientists aren’t yet sure if plants near the vents have absorbed any excess carbon dioxide, but they do know that some of the CO2 in the plants’ leaves comes from the vents. Atmospheric carbon dioxide contains a radioactive isotope called carbon-14 that isn’t present in the older carbon dioxide from the vents.

According to Williams, plants near the vents get about 30 percent of their CO2 from gas released from rocks. The percentage of carbon-14 from the atmosphere gradually increases as plant samples are collected farther and farther from the geological sources of gas.

Plants near the vents show some interesting physiological changes. Leaves near the vents contain less protein than those farther away.

“The ones [leaves] that are closer to the vents have less nutritional value, based on our initial analysis,” said Williams. “If you see the same response in the forage species; that is going to have implications for how the large herbivores interact with the vegetation. They’ll have to eat more to sustain themselves.”

These plants also don’t use water as efficiently as plants that rely solely on atmospheric carbon. “What we’re finding is that the plants photosynthesize less effectively in presence of high CO2, which is contrary to what other studies have shown,” said Williams. “The little pores in their leaves are opening up more and likely losing more water.”



Weeds benefit

“This study allows us to get a glimpse into the future about how plants will regulate their carbon and water cycles,” he continued. “We’re investigating that process and how that process is going to change if you take our results and expand them to the whole landscape. Then we can begin to understand how watersheds might behave in the future.”

Sharma and Williams also think that increased CO2 will help some invasive plants like Dalmatian toadflax expand into ranges by out-competing native plants. “We think it’s going to help these weeds because they are very fast-growing,” said Williams. “Other research has shown that fast growing weeds respond positively to elevated levels of CO2.”

Williams acknowledges that the research is still in its early phases. “There’s a lot of unknowns,” he said.

One of those unknowns is if plants near the vents are actually using more carbon dioxide than plants under normal atmospheric conditions. Regardless, Yellowstone’s geology could yield important clues about the future of life on earth. Weeds might be more invasive in the future, plants might need more water to grow, and animals might need more plants to get the same amount of protein.

According to Sharma, another avenue of research might be to see how elevated CO2 affects other plants that animals eat such as willows and grasses. One of the advantages of using Yellowstone’s naturally high concentrations of CO2 is that these types of studies are “very low cost,” she said.