Tropical CO2 Fertilization using Volcanic CO2: Results from a Recent CO2 Mapping Field Campaign at Volcán Rincón de la Vieja in Costa Rica
Abstract
Free Air CO2 Enrichment (FACE) studies are invaluable for understanding effects of CO2 fertilization, but have been absent in the tropics, and limited to relatively small spatial and temporal scales. Naturally occurring volcanic landscapes where CO2 is degassed through the soil provide a unique opportunity to explore the effects of elevated CO2 emissions on tropical ecosystems. We conducted a CO2 mapping field campaign in Spring 2020 at Volcán Rincón de la Vieja, Costa Rica in support of this overarching objective.
We focused measurement activities along fault lines identified from existing geologic maps and known degassing areas on the forested flanks, far from the volcanic crater, where cold gas seeps continuously emit excess volcanic CO2 through the soil. We targeted emission hotspots, sampling with accumulation chambers around hotspots and working outward until CO2 concentrations declined to ambient. Our measurements spanned two distinct ecosystems: humid rainforests of the north flank of the volcano and low and high-elevation seasonally dry forests on the south. At over 700 points, we measured CO2 flux emissions from the soil surface as well as CO2 concentrations at 0.5 m and 1 m above ground. At ground level, typical soil gas flux values ranged from 0.1 to ~4 ppm/sec (0.1 to 24 gCO2/m2/day) and up to 24 ppm/sec (666 gCO2/m2/day). CO2 concentrations at 0.5 and 1 m typically ranged between 400 and 600 ppm, with values up to 1200 ppm. The CO2 measurements are invaluable for establishing a spatial baseline map of elevated CO2 emission hotspots throughout the Rincón de la Vieja landscape and established the most comprehensive volcanic CO2 dataset ever conducted on the lower flanks of a Costa Rican volcano. Above ground measurements of CO2 concentration have potential applications in analyzing downslope flow and daytime turbulent mixing under the canopy. Further analysis necessitates repeat measurements, links to tree carbon isotopes, and large eddy simulation forward modeling of emissions, to refine how and where the volcanically emitted CO2 interacts with tree canopies. We are currently exploring a diverse set of high-resolution satellite remote sensing datasets for links between vegetation properties and our CO2 baseline map.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB129...05N
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES