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Morton et al. ReplyMultiple mechanisms could lead to up-regulation of dry-season photosynthesis in Amazon forests, including canopy phenology and illumination geometry. We specifically tested two mechanisms for phenology-driven changes in Amazon forests during dry-season months, and the combined evidence from passive optical and lidar satellite data was incompatible with large net changes in canopy leaf area or leaf reflectance suggested by previous studies. We therefore hypothesized that seasonal changes in the fraction of sunlit and shaded canopies, one aspect of bidirectional reflectance effects in Moderate Resolution Imaging Spectroradiometer (MODIS) data, could alter light availability for dry-season photosynthesis and the photosynthetic capacity of Amazon forests without large net changes in canopy composition. Subsequent work supports the hypothesis that seasonal changes in illumination geometry and diffuse light regulate light saturation in Amazon forests. These studies clarify the physical mechanisms that govern light availability in Amazon forests from seasonal variability in direct and diffuse illumination. Previously, in the debate over light limitation of Amazon forest productivity, seasonal changes in the distribution of light within complex Amazon forest canopies were confounded with dry-season increases in total incoming photosynthetically active radiation. In the accompanying Comment, Saleska et al. do not fully account for this confounding effect of forest structure on photosynthetic capacity.
Document ID
20170003059
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Morton, Douglas C.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Nagol, Jyoteshwar
(Maryland Univ. College Park, MD, United States)
Carabajal, Claudia C.
(Sigma Space Corp. Lanham, MD, United States)
Rosette, Jacqueline
(Maryland Univ. College Park, MD, United States)
Palace, Michael
(New Hampshire Univ. Durham, NH, United States)
Cook, Bruce D.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Vermote, Eric F.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Harding, David J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
North, Peter R. J.
(University Coll. Swansea, United Kingdom)
Date Acquired
April 6, 2017
Publication Date
March 16, 2016
Publication Information
Publication: Nature: Brief Communication Arising
Publisher: Macmillan Publishers Limited
Volume: 531
Issue: 7594
ISSN: 0028-0836
e-ISSN: 1476-4687
Subject Category
Meteorology And Climatology
Earth Resources And Remote Sensing
Report/Patent Number
GSFC-E-DAA-TN40869
Distribution Limits
Public
Copyright
Other

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