Thursday, August 15, 2019: 2:10 PM
L005/009, Kentucky International Convention Center
Trina L. Merrick1,2,3, Ralf Bennartz4, Stephanie Pau5, Maria Luisa Jorge6, Thiago Sanna Freire Silva7 and John Rausch2, (1)Geography, Florida State University, Tallahassee, FL, (2)Earth and Environmental Sciences, Vanderbilt University, Nashville, TN, (3)SFRC/SPECLab, University of Florida, Gainesville, FL, (4)Space Science and Engineering Center, University of Wisconsin – Madison, Madison, WI, (5)Department of Geography, Florida State University, Tallahassee, FL, (6)Earth & Environmental Sciences, Vanderbilt University, Nashville, TN, (7)Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista (Unesp), Rio Claro, Brazil
Background/Question/Methods: Tropical vegetation plays a major role in the carbon budget. Uncertainties in gross primary production (GPP), the largest flux component, hamper our understanding of feedbacks under climate change. Satellite-based solar-induced fluorescence (SIF) has been shown to have an empirical link to GPP in multiple ecosystems specific to vegetation type, thus is a promising tool to address current uncertainties in carbon fluxes at ecosystem to continental scales. However, SIF in the tropics has not been evaluated at these scales. Studies utilizing satellite-based SIF in South America have concentrated on Amazonian tropical forest, while SIF in other regions and for other vegetation classes remain unexamined. we examined three years of SIF data in the six Brazilian biomes (Amazon, Atlantic Forest, Caatinga, Cerrado, Pampa, and Pantanal) utilizing Orbiting Carbon Observatory-2 (OCO-2) observations to answer the following: (1) What are the biome-scale and vegetation class-scale distributions of SIF across Brazil? (3) How does the phenology of SIF (seasonal integrated SIF metrics) compare among vegetation classes within and across biomes and are differences captured based on the length of the seasons? (3) What is the relationship (strength and direction) of vegetation class-scale SIF to T
can, T
air, and VPD?
Results/Conclusions: We show evergreen broadleaf (EBF) SIF is significantly higher in all biomes (p<0.01) than other vegetation classes (deciduous broadleaf (DBF), grassland (GRA), savannas (SAV), and woody savannas (WSAV)). Our results show that SIF in all vegetation classes within every biome have a measureable seasonality. EBF SIF in every class had higher integrated SIF than other classes within each biome, with Amazon SIF having the highest year-round values of integrated SIF and the smallest seasonal pule integrated SIF. Surprisingly, the Pantanal EBF had the highest integrated SIF with a large seasonal pulse. Our evaluation of SIF of vegetation classes showed that relationships were strongest between SIF and vapor pressure deficit (VPD) in most instances, followed by canopy temperature Tcan, while air temperature (Tair) had the least number of biome~vegetation classes with stronger correlations than Tcanor VPD.
