MSA: Rapid assessment of the carbon cycle consequences of ecosystem disturbances

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Photosynthesis is the process by which plants use energy from sunlight to power their growth and consumption of carbon dioxide from the atmosphere. It is a critical ecosystem activity that is highly sensitive to fire and other extreme events that often occur quickly. The 2020 United States wildfire season was the most severe on record and it is important to understand how ecosystems respond to such disturbances. The United States has long been a leader in the development of geostationary satellites – commonly known as weather satellites – that measure the ground and atmosphere every few minutes. A new sensor called the Advanced Baseline Imager (ABI) on the Geostationary Operational Environment Satellites (GOES) can now make measurements related to photosynthesis and can do so nearly in real time. In the first study of its kind, this research will measure ecosystem carbon consumption using ABI observations and compare it to ground-based measurements made by sensors that are part of the National Ecological Observation Network (NEON) in nearly 50 sites across the United States. These observations will be used to understand the daily pattern of ecosystem carbon uptake across different ecosystems and how it can change rapidly in response to extreme events, especially wildfires. This project will also create educational materials and ‘virtual field trips’ for high school students who have been disproportionally impacted by recent travel disruptions, and to train groups of Native American undergraduates in the use of open source data on the environment.Gross primary productivity (GPP) is often measured using eddy covariance on half-hourly timescales at the ecosystem scale and ‘upscaled’ to larger regions using polar-orbiting satellites to create retrospective weekly to annual products. The new GOES ABI measures visible and near-infrared reflectance at the surface at a pixel size of ~1 km and can thus measure the normalized difference vegetation index (NDVI) and other indices to estimate GPP from space at time scales of minutes. GOES has long been used to monitor extreme events, to estimate ecosystem water and temperature stress, and to measure direct and diffuse solar radiation, all of which are important drivers of GPP. In other words, GPP can now be measured in near real-time at time scales of minutes and at spatial resolutions similar to the Moderate Resolution Imaging Spectroradiometer (MODIS), yet this opportunity has remained unexplored to date. This project will test the hypotheses that 1) diffuse photosynthetically active radiation (PAR) is a necessary input for satellite-based GPP estimates because it illuminates the canopy volume more efficiently than direct PAR, 2) that the 2020 California wildfires decreased GPP at nearby NEON towers because smoke decreased total PAR, and 3) that the GPP at NEON towers near the 2020 Colorado wildfires was enhanced by a greater fraction of diffuse PAR. Addressing these hypotheses will improve understanding of the immediate impacts of extreme events on carbon cycling. Project materials will also be used to create lessons for high school students that follow Next-Generation Science Standards and will train undergraduate students from Tribal Colleges on environmental data science early in their college careers when attrition from STEM fields tends to be high among all students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.