The drying up of the biosphere reveals the scent of a troubled ecosystem

Findings from an unprecedented drought experience in the biosphere underscore the importance of the molecular compounds often associated with fragrance in determining when an ecosystem is in distress.

Have you ever wondered what gives a forest a fresh pine scent? The answer is the molecular compound pinene, a type of monoterpene that plants release naturally. Each year plants pump approximately 100 million tons of monoterpenes into the atmosphere, where they play an important role in cloud formation.

The study was published in temper nature It explores how and under what conditions plants emit these volatile organic compounds, or VOCs, into the atmosphere. The findings may help scientists discover when an ecosystem is in distress and better understand how the Earth is trying to adapt in the face of a hotter, drier future.

The study is one of many that come from a Controlled dehydration experience Conducted in the university’s Biosphere 2, which was originally built to create self-sustaining ecosystems.

John Adams, Biosphere 2 Vice President and Chief Operating Officer says at the start of the project. “This gives scientists a really unique opportunity to get everything in order so that they can monitor and collect data that is often difficult or impossible to obtain in the field.”

For three months, the research team put the 30-acre “rainforest under glass” through moderate and then severe drought stress. The experiment, called Water, Atmospheric, and Life Dynamics – or WALD, a German word for “forest” – began to capture every bit of data possible during the drought and reprocessing process.

With more than two miles of Teflon tubes, 133 sensors, and 423 data-collecting points throughout the forest, the team collected measurements on everything from the microbiome and deep-water soil processes to carbon pool and volatile organic compound emissions.

Many VOCs have a unique scent, explains Laura Meredith, who helped lead the B2 WALD project and is a co-author on the latest study. For example, forests smell of pine and isoprene, while the chemical compound geosmin gives the soil an earthy flatness and contributes to the characteristic smell of rain in the air.

“There are many different types of VOCs that plants release into the atmosphere,” says Meredith, an associate professor in the School of Natural Resources and Environment in the university’s School of Agriculture and Life Sciences and a member of BIO5.

“If we can identify their unique signatures and the biological processes behind them, we can fly a plane over the Amazon rainforest, for example, and basically measure and detect what’s happening on Earth.”

During the B2 WALD project, Meredith served as the Rainforest Manager for Biosphere 2 and brought together 90 scientists from five different countries to monitor the resilience and vulnerability of plants and microbes. The project’s scientific expertise spanned all aspects of environmental stress, including hydrology, vegetation, soil and atmospheric sciences.

During a controlled drought experiment, researchers measured the hourly emissions of several monoterpenes, including pinene, camphene, limonene, terpenes, and isoprene to better understand how and when plants release VOCs.

The researchers found that plants not only release more of these VOCs under stress but also shift their emissions later in the day. And there may be a good reason for that, according to atmospheric scientist and study co-author Jonathan Williams.

“We suspect that the subsequent release of monoterpenes increases the likelihood of clouds forming above JungleSays Williams, project leader of the Max Planck Institute for Chemistry in Mainz, Germany.

“The higher the air temperature during the day, the higher the vertical mixing of the air, allowing reactive volatiles to reach higher layers of air where they have a greater chance of becoming hazy particles and eventually cloud cores,” Williams explains.

In other words, when an ecosystem is in a drought, plants may use volatile organic compounds to drive cloud formation and bring in much-needed rain.

The study underscores the extent to which VOCs are involved in communication, defense and signaling between soil microbes, plants, and the atmosphere, Meredith says.

Meredith will continue her exploration of VOCs with a recent grant from the Department of Energy. Along with ecosystem genome expert Angel Parasite, associate professor and ecologist in the College of Agriculture and Life Sciences, Meredith will explore carbon sequestration through soil, microbe, and plant interactions.

“Having explored the impact of volatile organic compounds on the atmosphere, we will now turn our attention to how these carbon-bearing molecules affect soils and their ability to sequester and store carbon,” Meredith says. “Do plants and microbes pump VOCs into the ground, as they do into the atmosphere, and what processes help ensure that carbon stays underground?”

source: University of Arizona