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Scaling photosynthesis in Amazonian ecosystems: from forest to savanna, from seasons to extreme events1Huete, A.R., 2Dye, D., 3Saleska, S.R., 1,3Restrepo-Coupe, N., 10Amaral, D., 4Didan, K., 3Wu, J., 5Marostica, S., 6Shimabukuro, Y., 5Nelson, B., 7da Rocha, H., 8Manzi, A., 9Kobayashi, H., 8Araújo A.

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Seasonality in Amazon Forests from MODIS, Hyperion, and Eddy Flux Tower (30m to >1km footprints)

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Hyperion (30m) based dry season responses ofPrimary, secondary, and converted forests

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Scaling up tropical forest characteristics and radiation components 3-D canopy photosynthesis model (FLiES)

1 Plant Functional Biology & Climate Change, Univ of Technology Sydney, Australia2 U.S Geological Survey, Flagstaff, Arizona , USA3 Dept. Ecology & Evolutionary Biology, University of Arizona, Tucson, U.S.A.4 Dept. Electrical & Computer Engineering, University of Arizona, Tucson, U.S.A.5 National Institute for Amazon Research (INPA), Manaus, Brazil6 Instituto Nacional de Pesquisas Espaciais (INPE), São José dos Campos, Brazil7 Universidade de Sao Paulo, Sao Paulo, Brazil 8 National Institute for Amazon Research (INPA), Manaus, Brazil9 Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Japan10 UFOPA Biotechnology and Forest Institute, Santarem, Brazil

Motivation

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Remote sensing methods offer potentially powerful insight into the response of vegetation to climatic variability, a particularly pressing question in Amazonian forests in light of recently observed contrasting responses to two widespread droughts in 2005 and 2010. While widespread increases in MODIS Enhanced Vegetation Index (EVI) (a photosynthetic "green-up") of forests were observed during the intense drought of July, August, September 2005, the pattern was reversed in 2010 when there were widespread EVI declines during a similarly intense drought in the same months.

However, remote sensing approaches for studying Amazonian drought have also been criticized as vulnerable to atmospheric aerosol and cloud artifacts, calling into question the reliability of these results.Here we introduce a new 3-year project that aims to simultaneously address the scientific question of vegetation response to climate, and the quality and reliability issues of remote sensing methods. The various approaches to be used in this project to integrate long-term in-situand remote sensing observations of Amazonian ecosystems are presented along with some preliminary examples that highlight leaf- and canopy-scale optics with gas exchange measures.

[Saleska et al., 2007].

Half-hourly "local" remote sensing (spectral) images of vegetation (TETRACAM) and full-sky radiometer images of incoming radiation fields enable new sampling schemes for compositing to daily and weekly values as well as to capture canopy structure –interactions with light. (a hyperspectral camera will be mounted in 2011)

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Tapajos National Forest K67 Weekly data & compositing schemesTETRACAM

Leaf scale optics and photosynthesis exhibit strong ‘seasonal’ variations, irrespective of LAI changes due to litterfall and flushing.

Our results will further be integrated into a parameterized and sophisticated 3-D canopy photosynthesis model (FLiES) in order to scale up tropical forest characteristics and radiation components (including aerosol-, cloud-, and subcanopy-influenced effects of diffuse radiation fraction and angular distribution). These initial results suggest that integrating imagery from satellites and towers, and linking these to ecosystem fluxes will provide a powerful tool for understanding the dynamics of vegetation-climate interactions in tropical Amazônia.

Examples of diurnal observations separated into direct and diffuse canopy reflectances and direct and diffuse irradiances onto a panel reference for light interaction analysis on canopy greening.

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Acknowledgements: NASA grant: Scaling photosynthesis in Amazonian ecosystems: from forest to savanna, from seasons to extreme events and NSF PIRE: Carbon, Water and Vegetation Dynamics of Amazon Forests Under Climatic Variability and Change Award ID: 0730305

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Time series for eight day average spectral band scaled digital counts (uncorrected) for the Tetracam. The images include soil, leaves, shadows, bark soil and all forest components

*updated to C5 from Saleska et al. [2007]

Hyperion data with 30m cloud & aerosol screening confirm continuous greening from start to end of dry season (left), while eddy covariance Pg is tightly related with MODIS EVI and Hyperion results.

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Tapajos National Forest K67 Diurnal data & compositing schemesTETRACAMMay 13, 2010

Amazon field ASD Leaf Spectra: Lauraceae (Aiduga Myristicoidis)

Amazon field ASD Leaf Spectra: Lauraceae (Aiduga Myristicoidis)

Very young leaf(1)Very young leaf(2)Big young leaf(1)Big young leaf(2)Mature leaf(1)Mature leaf(2)

Mature leafMature leaf w/lesionScrape mature leaf to the green underneathMature leaf with whitish epiphyllMature leaf with fresh yellowingBrown part of leafEntire brown leaf

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We are developing a scheme to transform the spectral digital counts into image reflectances using the white reference panel along with sunshine pyranometer measurements.

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