title: Large seasonal swings in leaf area of Amazon rainforests.
abstract: Despite early speculation to the contrary, all tropical forests studied to date display seasonal variations in the presence of new leaves, flowers, and fruits. Past studies were focused on the timing of phenological events and their cues but not on the accompanying changes in leaf area that regulate vegetation-atmosphere exchanges of energy, momentum, and mass. Here we report, from analysis of 5 years of recent satellite data, seasonal swings in green leaf area of approximately 25% in a majority of the Amazon rainforests. This seasonal cycle is timed to the seasonality of solar radiation in a manner that is suggestive of anticipatory and opportunistic patterns of net leaf flushing during the early to mid part of the light-rich dry season and net leaf abscission during the cloudy wet season. These seasonal swings in leaf area may be critical to initiation of the transition from dry to wet season, seasonal carbon balance between photosynthetic gains and respiratory losses, and litterfall nutrient cycling in moist tropical forests.
authors.affiliation: Department of Geography and Environment, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, USA.
authors.forename: Ranga B
authors.initials: RB
authors.lastname: Myneni
authors.forename: Wenze
authors.initials: W
authors.lastname: Yang
authors.forename: Ramakrishna R
authors.initials: RR
authors.lastname: Nemani
authors.forename: Alfredo R
authors.initials: AR
authors.lastname: Huete
authors.forename: Robert E
authors.initials: RE
authors.lastname: Dickinson
authors.forename: Yuri
authors.initials: Y
authors.lastname: Knyazikhin
authors.forename: Kamel
authors.initials: K
authors.lastname: Didan
authors.forename: Rong
authors.initials: R
authors.lastname: Fu
authors.forename: Robinson I
authors.initials: RI
authors.lastname: Negrón Juárez
authors.forename: Sasan S
authors.initials: SS
authors.lastname: Saatchi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Ichii
authors.forename: Nikolay V
authors.initials: NV
authors.lastname: Shabanov
authors.forename: Bin
authors.initials: B
authors.lastname: Tan
authors.forename: Piyachat
authors.initials: P
authors.lastname: Ratana
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Privette
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Morisette
authors.forename: Eric F
authors.initials: EF
authors.lastname: Vermote
authors.forename: David P
authors.initials: DP
authors.lastname: Roy
authors.forename: Robert E
authors.initials: RE
authors.lastname: Wolfe
authors.forename: Mark A
authors.initials: MA
authors.lastname: Friedl
authors.forename: Steven W
authors.initials: SW
authors.lastname: Running
authors.forename: Petr
authors.initials: P
authors.lastname: Votava
authors.forename: Nazmi
authors.initials: N
authors.lastname: El-Saleous
authors.forename: Sadashiva
authors.initials: S
authors.lastname: Devadiga
authors.forename: Yin
authors.initials: Y
authors.lastname: Su
authors.forename: Vincent V
authors.initials: VV
authors.lastname: Salomonson
mesh_terms: D001938:Brazil; D005843:Geography; D009929:Organ Size; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000254:growth & development* / Q000528:radiation effects; D011891:Rain; D017215:Satellite Communications / Q000295:instrumentation; D012621:Seasons; D013472:Sunlight; D013997:Time Factors; D014197:Trees / Q000033:anatomy & histology* / Q000254:growth & development* / Q000528:radiation effects