| Title | Sunlight mediated seasonality in canopy structure and photosynthetic activity of Amazonian rainforests |
| Authors | Bi, Jian Knyazikhin, Yuri Choi, Sungho Park, Taejin Barichivich, Jonathan Ciais, Philippe Fu, Rong Ganguly, Sangram Hall, Forrest Hilker, Thomas Huete, Alfredo Jones, Matthew Kimball, John Lyapustin, Alexei I. Mottus, Matti Nemani, Ramakrishna R. Piao, Shilong Poulter, Benjamin Saleska, Scott R. Saatchi, Sassan S. Xu, Liang Zhou, Liming Myneni, Ranga B. |
| Affiliation | Boston Univ, Dept Earth & Environm, Boston, MA 02215 USA. Univ E Anglia, Sch Environm Sci, Climat Res Unit, Norwich NR4 7TJ, Norfolk, England. UVSQ, CEA, CNRS, IPSL,LSCE, F-91191 Gif Sur Yvette, France. Univ Texas Austin, Dept Geol Sci, Austin, TX 78712 USA. NASA, Bay Area Environm Res Inst, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Biospher Sci Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Oregon State Univ, Coll Forestry, Corvallis, OR 97331 USA. Univ Technol Sydney, Plant Funct Biol & Climate Change Cluster, Sydney, NSW 2007, Australia. Univ Montana, Numer Terradynam Simulat Grp, Missoula, MT 59812 USA. NASA, Climate & Radiat Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Helsinki, Dept Geosci & Geog, FI-00014 Helsinki, Finland. NASA, Adv Supercomp Div, Ames Res Ctr, Moffett Field, CA 94035 USA. Peking Univ, Dept Ecol, Beijing 100871, Peoples R China. Chinese Acad Sci, Inst Tibetan Plateau Res, Beijing 100085, Peoples R China. Montana State Univ, Dept Ecol, Bozeman, MT 59717 USA. Univ Arizona, Dept Ecol & Evolutionary Biol, Tucson, AZ 85721 USA. Univ Calif Los Angeles, Inst Environm & Sustainabil, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Radar Sci & Engn Sect, Pasadena, CA 91109 USA. SUNY Albany, Dept Atmospher & Environm Sci, Albany, NY 12222 USA. |
| Keywords | Amazonian rainforests seasonality remote sensing MISR MODIS LEAF-AREA INDEX TROPICAL FOREST DRY SEASON MODIS CARBON PRODUCTIVITY VARIABILITY SENSITIVITY ALGORITHM PHENOLOGY |
| Issue Date | 2015 |
| Publisher | ENVIRONMENTAL RESEARCH LETTERS |
| Citation | ENVIRONMENTAL RESEARCH LETTERS.2015,10,(6). |
| Abstract | Resolving 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. Weattribute 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. |
| URI | http://hdl.handle.net/20.500.11897/419644 |
| ISSN | 1748-9326 |
| DOI | 10.1088/1748-9326/10/6/064014 |
| Indexed | SCI(E) EI |
| Appears in Collections: | 城市与环境学院 |
