Climate change is one of the most important issues in the world, today and into the future. Carbon dioxide (CO2) is one of the most abundant greenhouse gases (GHG) in our atmosphere, making it an essential gas to understand. Eosense’s waterproof CO2 probes are helping to answer climate change and mitigation questions by assisting the Baldocchi Lab at UC Berkeley in gathering the necessary data for their studies on the carbon dynamics of the Sacramento-San Joaquin Delta (SSJD). While their work is ongoing, interesting insights into the carbon dynamics of the SSJD have already been brought to light.
eosGP string for water column
The SSJD is crucial because:
With a better understanding of how current agricultural activity and restoration projects are influencing GHG fluxes, the goal of the Baldocchi Lab is to uncover an optimal balance between the SSJD’s uses.
Climate change is a recognized problem that has already impacted many places in the world, and for the State of California it has exacerbated severe multi-year droughts. During the 1800’s the land in the SSJD was converted from a wetland ecosystem into agricultural land, largely to provide fresh fruit to mine workers during the California Gold Rush. Today the SSJD is still used as economically important agricultural land, is a source for irrigation water that supplies more than 1 million acres of farmland, and provides drinking water to more than half of the population in the State of California (20 million).
The delta’s proximity to the ocean and artificially low elevation (-10 m / -30 ft), caused by agriculture-induced subsidence, makes it vulnerable to sea level rise. The combination of land subsidence and severe drought ultimately compromises both an important water source and the economically important agricultural land.
Restoring the land in the SSJD back to its original wetland state will help build up soils, making them less vulnerable to inundation by saltwater, thereby protecting the delta’s water supply. However, while restoring agricultural land back into wetland increases carbon sequestration, it also reduces the economic potential of the land and has the potential to release methane (CH4), which has 25 to 30 times the global-warming potential of CO2. Understanding how and where carbon is stored and how much is emitted by different land-use types in the SSJD will ultimately determine the balance between wetland restoration and continued agricultural use. This information will also allow for potential carbon sequestration opportunities and the development of a carbon credit system for the State of California.
The Baldocchi Lab at UC Berkeley has been studying the SSJD for eight years, and will continue to do so for at least another five years. The main questions they want answered are: What are the current CO2 and CH4 fluxes of the drained peatlands? How will changing the land type from drained peatlands to flooded wetland or rice paddies change these fluxes over time? Can a viable protocol be set up using the data from the project to implement a carbon offset program in the State of California with current and future restorative projects?
eosGPs buried in soil
The Baldocchi Lab needed to explain patterns they have been seeing in their eddy covariance flux data and chose the eosGP CO2 probes because of their waterproofness, low cost, and low power requirements. Powered by solar panels alone, the continuous data captured by the CO2 probes, installed in both water and soil, allowed for both short- and long-term insights. The probes have shed light on how water column thermal turnover affects CO2 emissions from the wetland, as well as revealed more about the subsurface CO2 dynamics of the alfalfa fields in the SSJD. Lastly, it was noted by the Baldocchi team that the probes do not artificially heat the soil as much as other probes, minimizing a potential source for biased results.
“The eosGP probes are great for measuring CO2 in wet environments – they can be buried directly in soil or used underwater without additional waterproofing. This one-piece sensor has a simple cable interface offering digital and analog outputs and has power requirements suitable for solar power. — Joe Verfaillie (Lab Manager, Baldocchi Lab)”
So far the study has shown that the oldest of the restored wetland sites appears to be sequestering less carbon than it did in when it was newly restored. One possible explanation for this is that the detrital layers have become thick enough that new growth is taking longer to get through. Since new growth typically stores more carbon, the attenuated growth may explain the unexpected decrease in sequestration observed.
The next revelation was the sharp decrease in soil CO2 levels in the alfalfa fields after mowing took place (Figure 1). This is likely due to the removal of the photosynthetic surface of the plants resulting in a decrease in photosynthesis, and consequently a decrease in root exudates. These exudates are metabolized by bacterial communities in the soil, which in turn respire it as CO2.
Figure 1. A large decrease in carbon dioxide concentration in the Twitchell Island (SSJD) alfalfa field after a mowing occurred. Concentration data was captured by three eosGP’s buried in the soil.
The Baldocchi Lab is undertaking this large project with the aim of establishing a baseline of GHG fluxes in the Sacramento-San Joaquin Delta in its current state, which is both agricultural land and restored wetland. Studying the different land-use types and understanding current GHG dynamics will help inform future management strategies on how best to move forward with restoration projects. The findings of the Baldocchi lab will also assist the state of California in assessing the potential for a carbon credit system.
Learn more about the Baldocchi Lab’s work at UC Berkeley website: http://nature.berkeley.edu/biometlab/