Large seasonal swings in leaf area of Amazon rainforests.
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.
Myneni
Ranga B
RB
Department of Geography and Environment, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, USA.
Yang
Wenze
W
Nemani
Ramakrishna R
RR
Huete
Alfredo R
AR
Dickinson
Robert E
RE
Knyazikhin
Yuri
Y
Didan
Kamel
K
Fu
Rong
R
Negrón Juárez
Robinson I
RI
Saatchi
Sasan S
SS
Hashimoto
Hirofumi
H
Ichii
Kazuhito
K
Shabanov
Nikolay V
NV
Tan
Bin
B
Ratana
Piyachat
P
Privette
Jeffrey L
JL
Morisette
Jeffrey T
JT
Vermote
Eric F
EF
Roy
David P
DP
Wolfe
Robert E
RE
Friedl
Mark A
MA
Running
Steven W
SW
Votava
Petr
P
El-Saleous
Nazmi
N
Devadiga
Sadashiva
S
Su
Yin
Y
Salomonson
Vincent V
VV
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