Sunlight mediated seasonality in canopy structure & photosynthetic activity of Amazonian rainforests

dc.contributor.authorBi, Jian
dc.contributor.authorKnyazikhin, Yuri
dc.contributor.authorChoi, Sungho
dc.contributor.authorPark, Taejin
dc.contributor.authorBarichivich, Jonathon
dc.contributor.authorCiais, Philippe
dc.contributor.authorFu, Rong
dc.contributor.authorGanguly, Sangram
dc.contributor.authorHall, Forrest
dc.contributor.authorHilker, Thomas
dc.contributor.authorHuete, Alfredo
dc.contributor.authorJones, Matthew
dc.contributor.authorKimball, John S.
dc.contributor.authorLyapustin, Alexei
dc.contributor.authorMottus, Matti
dc.contributor.authorNemani, Ramakrishna R.
dc.contributor.authorPiao, Shilong
dc.contributor.authorPoulter, Benjamin
dc.contributor.authorSaleska, Scott R.
dc.contributor.authorSaatchi, Sassan S.
dc.contributor.authorXu, Liang
dc.contributor.authorZhou, Liming
dc.contributor.authorMyneni, Ranga B.
dc.description.abstractResolving the debate surrounding the nature and controls of seasonal variation in the structure and metabolism of Amazonian rainforests is critical to understanding their response to climate change. In situ studies have observed higher photosynthetic and evapotranspiration rates, increased litterfall and leaf flushing during the Sunlight-rich dry season. Satellite data also indicated higher greenness level, a proven surrogate of photosynthetic carbon fixation, and leaf area during the dry season relative to the wet season. Some recent reports suggest that rainforests display no seasonal variations and the previous results were satellite measurement artefacts. Therefore, here we re-examine several years of data from three sensors on two satellites under a range of sun positions and satellite measurement geometries and document robust evidence for a seasonal cycle in structure and greenness of wet equatorial Amazonian rainforests. This seasonal cycle is concordant with independent observations of solar radiation. We attribute alternative conclusions to an incomplete study of the seasonal cycle, i.e. the dry season only, and to prognostications based on a biased radiative transfer model. Consequently, evidence of dry season greening in geometry corrected satellite data was ignored and the absence of evidence for seasonal variation in lidar data due to noisy and saturated signals was misinterpreted as evidence of the absence of changes during the dry season. Our results, grounded in the physics of radiative transfer, buttress previous reports of dry season increases in leaf flushing, litterfall, photosynthesis and evapotranspiration in well-hydrated Amazonian rainforests.en_US
dc.identifier.citationBi, Jian, Yuri Knyazikhin, Sungho Choi, Taejin Park, Jonathon Barichivich, Philippe Ciais, Rong Fu, Sangram Ganguly, Forrest Hall, Thomas Hilker, Alfredo Huete, Matthew Jones, John Kimball, Alexei I Lyapustin, Matti Mottus, Ramakrishna R. Nemani, Shilong Piao, Benjamin Poulter, Scott R. Saleska, Sassan S. Saatchi, Liang Xu, Liming Zhou, and Ranga B. Myneni. "Sunlight mediated seasonality in canopy structure & photosynthetic activity of Amazonian rainforests." Environmental Research Letters 10 (June 2015): 064014. DOI:
dc.rightsCC BY 4.0en_US
dc.titleSunlight mediated seasonality in canopy structure & photosynthetic activity of Amazonian rainforestsen_US
mus.citation.journaltitleEnvironmental Research Lettersen_US
mus.contributor.orcidPoulter, Benjamin|0000-0002-9493-8600en_US
mus.identifier.categoryLife Sciences & Earth Sciencesen_US
mus.relation.collegeCollege of Letters & Scienceen_US
mus.relation.universityMontana State University - Bozemanen_US


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