LVOC's Carbon Garden is a living laboratory
You might have visited the Livermore Valley Open Campus (LVOC) and wondered about the fenced-off open area full of bunch grasses and domes. This area is a living laboratory, where scientists are measuring carbon cycling between soil, plants and the air.
Soil carbon comprises the largest land-based pool of carbon on earth, making it a central component in the global carbon cycle. In addition to keeping carbon out of the atmosphere, this carbon pool also improves soil and crop nutrient levels, plant health, and resistance to environmental changes such as drought. To support these functions, LLNL researchers are studying the factors that help carbon remain in soil for as long as possible.
Plants play a major role in putting carbon into the soil through the processes of photosynthesis, root exudation and decaying plant and root material. Deeper carbon has been shown to persist longer, making deep-rooted plants a potential avenue for increasing soil carbon. Through the Carbon Garden, LLNL researchers are exploring the effectiveness of several deep-rooted grass species at keeping carbon in the soil, where it can have a large impact.
The Carbon Garden contains several drought-tolerant grass species with deep roots that are prevalent in California:
- the California native blue grama grass (Bouteloua gracilis)
- wild rye (Leymus condensatus)
- deer grass (Muhlenbergia rigens)
- a bioenergy crop switchgrass (Panicum virgatum)
Through two different methodologies, researchers are compiling carbon flow data on the individual plant level as well as the field level, providing an integrated view of how different grass species affect carbon flow in the area.
Studying carbon flow
The Carbon Garden features two different technologies for measuring carbon flow between the atmosphere, plants and soil. One method uses gas flux chambers, which continuously measure how much carbon gas is entering an individual plant through its leaves during photosynthesis, exiting its leaves at night through the process of “dark respiration” and being released via decomposition and root respiration into the soil around the plant.
The flux chambers measure the net amount of carbon moving between plants, soil and the atmosphere. This net flux reflects carbon lost from the system through respiration minus the carbon taken in during photosynthesis. Grasses that store carbon deeper in the soil and enhance long-term carbon persistence tend to produce more frequent and larger negative carbon flux measurements, indicating that more carbon is being taken in than released.
“This project is unique in its use of these large, transparent flux chambers capable of measuring both photosynthetic uptake and respiration,” says Shannon Brown, staff scientist in the Physical & Life Sciences Principal Directorate’s Atmospheric, Earth & Energy Division (AEED). “This approach enables us to precisely track the dynamics of carbon flow for each plant species.”
The other equipment used at the Carbon Garden is an eddy covariance tower, which measures carbon gas flux between the atmosphere and a larger area of land surface surrounding the garden. In addition to its flux measurements, the tower has instrumentation that records data about the weather in the local area. The data include:
- temperature
- relative humidity (a measure of water vapor in the air)
- incoming solar radiation
- rainfall
By including weather data in their experiments, the team can better understand the environmental factors leading to increased carbon uptake by the experimental grasses.
Together, these two streams of data provide insight into the broader impacts of deep-rooted grasses on the soil in which they are planted. Brown and Kari Finstad, also a staff scientist in AEED, are connecting the data from the eddy covariance tower with individual plant data from the chambers, hoping to determine which native grass species are most effective at storing carbon.
“Having a highly instrumented, long-term measurement site at LLNL creates valuable opportunities to study natural processes,” says Brown. “As an outdoor laboratory, it offers the flexibility to add more instrumentation or conduct additional studies in partnership with other researchers.”
Ultimately, they look to provide evidence that these grasses can be planted in areas of otherwise unused or water-intensive land — like the sections of grass in the middle of freeway ramps, as replacement for lawns, landscaping around institutions and more — to passively improve the amount of carbon in California’s soils and conserve water. Next time you’re at LVOC, consider making a stop at the Carbon Garden to learn more and see these experiments in action.
–Lilly Ackerman, Technical Information Department
