{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,28]],"date-time":"2026-10-28T11:44:19Z","timestamp":1793187859897,"version":"4.5.0"},"reference-count":40,"publisher":"National Academy of Sciences","issue":"33","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2010,8,17]]},"abstract":"<jats:p>Drought exerts a strong influence on tropical forest metabolism, carbon stocks, and ultimately the flux of carbon to the atmosphere. Satellite-based studies have suggested that Amazon forests green up during droughts because of increased sunlight, whereas field studies have reported increased tree mortality during severe droughts. In an effort to reconcile these apparently conflicting findings, we conducted an analysis of climate data, field measurements, and improved satellite-based measures of forest photosynthetic activity. Wet-season precipitation and plant-available water (PAW) decreased over the Amazon Basin from 1996\u22122005, and photosynthetically active radiation (PAR) and air dryness (expressed as vapor pressure deficit, VPD) increased from 2002\u20132005. Using improved enhanced vegetation index (EVI) measurements (2000\u20132008), we show that gross primary productivity (expressed as EVI) declined with VPD and PAW in regions of sparse canopy cover across a wide range of environments for each year of the study. In densely forested areas, no climatic variable adequately explained the Basin-wide interannual variability of EVI. Based on a site-specific study, we show that monthly EVI was relatively insensitive to leaf area index (LAI) but correlated positively with leaf flushing and PAR measured in the field. These findings suggest that production of new leaves, even when unaccompanied by associated changes in LAI, could play an important role in Basin-wide interannual EVI variability. Because EVI variability was greatest in regions of lower PAW, we hypothesize that drought could increase EVI by synchronizing leaf flushing via its effects on leaf bud development.<\/jats:p>","DOI":"10.1073\/pnas.0908741107","type":"journal-article","created":{"date-parts":[[2010,8,2]],"date-time":"2010-08-02T23:35:49Z","timestamp":1280792149000},"page":"14685-14690","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":277,"title":["Seasonal and interannual variability of climate and vegetation indices across the Amazon"],"prefix":"10.1073","volume":"107","author":[{"given":"Paulo M.","family":"Brando","sequence":"first","affiliation":[{"name":"Instituto de Pesquisa Ambiental da Amaz\u00f4nia, 66035-170 Bel\u00e9m, Brazil;"},{"name":"Department of Biology and School of Natural Resources and Environment and"},{"name":"Woods Hole Research Center, Falmouth, MA 02450"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Scott J.","family":"Goetz","sequence":"additional","affiliation":[{"name":"Woods Hole Research Center, Falmouth, MA 02450"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alessandro","family":"Baccini","sequence":"additional","affiliation":[{"name":"Woods Hole Research Center, Falmouth, MA 02450"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daniel C.","family":"Nepstad","sequence":"additional","affiliation":[{"name":"Woods Hole Research Center, Falmouth, MA 02450"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pieter S. A.","family":"Beck","sequence":"additional","affiliation":[{"name":"Woods Hole Research Center, Falmouth, MA 02450"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mary C.","family":"Christman","sequence":"additional","affiliation":[{"name":"Department of Statistics and Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611; and"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2010,8,2]]},"reference":[{"key":"e_1_3_3_1_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.1146961"},{"key":"e_1_3_3_2_2","doi-asserted-by":"publisher","DOI":"10.1175\/1520-0442(2000)013<0018:CEODAD>2.0.CO;2"},{"key":"e_1_3_3_3_2","doi-asserted-by":"publisher","DOI":"10.1029\/2001JD000717"},{"key":"e_1_3_3_4_2","doi-asserted-by":"publisher","DOI":"10.1175\/1520-0442(1991)004<0957:ADARCC>2.0.CO;2"},{"key":"e_1_3_3_5_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1529-8817.2003.00772.x"},{"key":"e_1_3_3_6_2","doi-asserted-by":"publisher","DOI":"10.1038\/nature06960"},{"key":"e_1_3_3_7_2","doi-asserted-by":"publisher","DOI":"10.1175\/2007JCLI1600.1"},{"key":"e_1_3_3_8_2","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2007.0036"},{"key":"e_1_3_3_9_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365-3040.2005.01407.x"},{"key":"e_1_3_3_10_2","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2007.0027"},{"key":"e_1_3_3_11_2","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2007.0028"},{"key":"e_1_3_3_12_2","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2007.0019"},{"key":"e_1_3_3_13_2","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2007.0032"},{"key":"e_1_3_3_14_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0133045100"},{"key":"e_1_3_3_15_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.1091165"},{"key":"e_1_3_3_16_2","article-title":"Seasonal controls on the exchange of carbon and water in an Amazonian rain forest","volume":"112","author":"Hutyra LR","year":"2007","unstructured":"LR Hutyra, et al., Seasonal controls on the exchange of carbon and water in an Amazonian rain forest. J Geophys Res 112, G04099. (2007).","journal-title":"J Geophys Res"},{"key":"e_1_3_3_17_2","first-page":"429","volume-title":"Geophys Monogr Ser","author":"Meir P","year":"2009","unstructured":"P Meir, et al., The effects of drought on Amazonian rainforests. Geophys Monogr Ser, pp. 429\u2013459, 10.1029\/2008GM000882. (2009)."},{"key":"e_1_3_3_18_2","doi-asserted-by":"publisher","DOI":"10.1007\/s00442-005-0108-2"},{"key":"e_1_3_3_19_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.1164033"},{"key":"e_1_3_3_20_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.1146663"},{"key":"e_1_3_3_21_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0034-4257(02)00096-2"},{"key":"e_1_3_3_22_2","doi-asserted-by":"publisher","DOI":"10.1029\/2009GL042154"},{"key":"e_1_3_3_23_2","doi-asserted-by":"publisher","DOI":"10.1890\/07-1929.1"},{"key":"e_1_3_3_24_2","first-page":"1632","article-title":"The El Nino Southern Oscillation, variable fruit production, and famine in a tropical forest","volume":"80","author":"Wright SJ","year":"1999","unstructured":"SJ Wright, C Carrasco, O Calderon, S Paton, The El Nino Southern Oscillation, variable fruit production, and famine in a tropical forest. Ecology 80, 1632\u20131647 (1999).","journal-title":"Ecology"},{"key":"e_1_3_3_25_2","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2007.0031"},{"key":"e_1_3_3_26_2","doi-asserted-by":"publisher","DOI":"10.1890\/06-1046.1"},{"key":"e_1_3_3_27_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0611338104"},{"key":"e_1_3_3_28_2","doi-asserted-by":"publisher","DOI":"10.1029\/2005GL025583"},{"key":"e_1_3_3_29_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.rse.2004.08.015"},{"key":"e_1_3_3_30_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0034-4257(02)00091-3"},{"key":"e_1_3_3_31_2","doi-asserted-by":"crossref","unstructured":"DC Nepstad et al. The role of deep roots in the hydrological and carbon cycles of Amazonian forests and pastures. PhD thesis.  (Yale Univ New Haven CT 1994).","DOI":"10.1038\/372666a0"},{"key":"e_1_3_3_32_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0065-2504(08)60029-X"},{"key":"e_1_3_3_33_2","doi-asserted-by":"publisher","DOI":"10.1029\/2007JG000590"},{"key":"e_1_3_3_34_2","doi-asserted-by":"publisher","DOI":"10.1086\/285600"},{"key":"e_1_3_3_35_2","doi-asserted-by":"publisher","DOI":"10.1007\/s00468-002-0185-3"},{"key":"e_1_3_3_36_2","doi-asserted-by":"publisher","DOI":"10.2307\/1939307"},{"key":"e_1_3_3_37_2","doi-asserted-by":"publisher","DOI":"10.1175\/1087-3562(2003)007<0001:GPTCAA>2.0.CO;2"},{"key":"e_1_3_3_38_2","doi-asserted-by":"publisher","DOI":"10.1029\/2001JD000360"},{"key":"e_1_3_3_39_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0038-092X(97)00001-7"},{"key":"e_1_3_3_40_2","doi-asserted-by":"publisher","DOI":"10.1017\/CBO9780511801686"}],"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.0908741107","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,12]],"date-time":"2022-04-12T18:26:54Z","timestamp":1649788014000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/full\/10.1073\/pnas.0908741107"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2010,8,2]]},"references-count":40,"journal-issue":{"issue":"33","published-print":{"date-parts":[[2010,8,17]]}},"alternative-id":["10.1073\/pnas.0908741107"],"URL":"https:\/\/doi.org\/10.1073\/pnas.0908741107","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[2010,8,2]]},"assertion":[{"value":"2010-08-02","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}