Collaborative Research: Links Between Long-Term Soil Carbon Storage and Canopy Properties in Tropical Forests

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Atmospheric carbon dioxide (CO2) has been increasing, leading to changes in Earth's climate, but it is unclear how much of that CO2 can be drawn back down by the planet's ecosystems and stored in soils and plants. This project focuses on understanding that CO2 draw-down and storage process with particular focus on tropical forests, which are one of the most carbon-rich ecosystems on Earth. New space technologies have recently improved the ability to measure plant carbon storage using satellite remote sensing. However, a large proportion of carbon storage occurs in soils, where dead plant material can be stored for much longer periods than in live plants. This study uses new remote sensing technologies and field-based measurements to link plant and soil carbon storage. The project integrates these two types of measurements through a new predictive framework to broaden understanding across space and time. Broader impacts for this project include the training of several undergraduate students and a graduate student (UCLA) in cutting-edge geographic and ecological technologies, and creation of a Field Technician Training Program for Latin American college students and community members to expand the work force in science and technology. At the broad scale, this research will also improve predictability of carbon storage across tropical forest ecosystems, providing insights for management of carbon sequestration.Soil carbon (C) dynamics present one of the largest sources of uncertainty in global C cycle models, with tropical forest soils containing some of the largest terrestrial C stocks. The interactions between aboveground C uptake by plants, transfer of this C to the forest floor, and subsequent loss or storage of this C in soils must be better understood to predict how climate change may alter large-scale and long-term soil C storage. This research will advance understanding of humid and seasonal tropical biomes through the intersection of modeling, remote sensing, and in situ field measurements across geological and rainfall gradients, focusing on the links between canopy and soil properties. The research will include measures of the total fluxes of C into forests using remote sensing measures of canopy fluorescence, and use these measures, together with knowledge of geology and soil nutrients, to predict soil C storage. The central hypothesis is that: Spatial variation in canopy properties, which reflect geology and the availability of scarce soil nutrients, are directly linked to landscape-scale patterns of long-term soil C storage in tropical forests. Soil phosphorus, rainfall, and canopy species composition will be assessed for their roles in driving soil C storage. The approach spans scales from nanometer organo-mineral associations in soils, to 3 km2 measures of forest plant growth. The study will be conducted in a variety of tropical forests in Panama in collaboration with the Smithsonian Tropical Research Institute. To better understand how tropical forests around the world store carbon, beyond the spatial and temporal scales of the field study, measures will also be integrated into an existing ecosystem model.