TY - JOUR
T1 - Leaf flush drives dry season green-up of the Central Amazon
AU - Lopes, Aline Pontes
AU - Nelson, Bruce Walker
AU - Wu, Jin
AU - Graça, Paulo Maurício Lima de Alencastro
AU - Tavares, Julia Valentim
AU - Prohaska, Neill
AU - Martins, Giordane Augusto
AU - Saleska, Scott R.
N1 - Funding Information:
We thank the Max Planck Society; the German Federal Ministry of Education and Research (BMBF contract 01LB1001A); the Brazilian Ministry of Science, Technology and Innovation (MCTI/FINEP contract 01.11.01248.00); the Amazonas State University (UEA); Amazonas State Foundation for Research (FAPEAM); the Large-scale Biosphere-Atmosphere Experiment of Brazil's National Institute for Amazon Research (LBA/INPA); and the Uatumã Sustainable Development Reserve of Amazonas State's Secretariat of Sustainable Development (SDS/CEUC/RDS-Uatumã). FAPEAM financed the GoAmazon project “Understanding the Response of Photosynthetic Metabolism in Tropical Forests to Seasonal Climate Variations”. The Brazilian National Council for Technological and Scientific Development (CNPq) provided fellowships to APL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank Thomas Disper, Reiner Ditz and Hermes Braga Xavier of the ATTO logistics team; Marta Sá, Antonio Huxley and Leonardo Oliveira of the Micrometeorological group of LBA/INPA; Antônio Manzi and Marciel José Ferreira for logistic and financial support; and Carolina Castilho for analysis of PPBio tree inventories. Alexei Lyapustin and Yujie Wang developed the MODIS MAIAC EVI processing procedures and Kaiyu Guan helped extract ten years data for the ATTO site.
Publisher Copyright:
© 2016 Elsevier Inc.
PY - 2016/9/1
Y1 - 2016/9/1
N2 - Understanding how land surface seasonality emerges from individual tree crown phenology is a key challenge of tropical ecology. We used daily images over a full year from a tower-mounted RGB camera to quantify the leaf phenology of 267 individual tree crowns in an evergreen Central Amazon forest. The Green Chromatic Coordinate, an index of each crown's greenness, showed rapid large-amplitude positive and negative changes, each generally occurring once per year. Rapid increase was attributed to leaf flushing and occurred in 85% of all crowns. Rapid negative change occurred in 42% of individuals, caused mostly by massive pre-flush leaf abscission (31% of all crowns). Flushing was concentrated in the five driest months (55% of crowns) compared to the five wettest months (10%). Inter-crown variance of greenness was lowest in the wet season when fewer crowns were abruptly abscising or flushing leaves. With a one month lead, flushing frequency closely tracked seasonal light availability (R = 0.89) and was inversely correlated with rainfall (R = -. 0.88). We linked the post-flush age of each crown's leaf cohort to the Enhanced Vegetation Index (EVI) of crowns at different phenostages on a nadir view QuickBird image. When aggregated to landscape-scale, this camera-based EVI closely followed (R = 0.95) the MODIS MAIAC EVI of the same site, fully corrected for sun-sensor geometry effects. Leaf phenology therefore drives the dry season green-up detected by MODIS in the Central Amazon. It is also consistent with evolutionary strategies to couple photosynthetic efficiency with light availability and to avoid predation and disease on vulnerable young leaves.
AB - Understanding how land surface seasonality emerges from individual tree crown phenology is a key challenge of tropical ecology. We used daily images over a full year from a tower-mounted RGB camera to quantify the leaf phenology of 267 individual tree crowns in an evergreen Central Amazon forest. The Green Chromatic Coordinate, an index of each crown's greenness, showed rapid large-amplitude positive and negative changes, each generally occurring once per year. Rapid increase was attributed to leaf flushing and occurred in 85% of all crowns. Rapid negative change occurred in 42% of individuals, caused mostly by massive pre-flush leaf abscission (31% of all crowns). Flushing was concentrated in the five driest months (55% of crowns) compared to the five wettest months (10%). Inter-crown variance of greenness was lowest in the wet season when fewer crowns were abruptly abscising or flushing leaves. With a one month lead, flushing frequency closely tracked seasonal light availability (R = 0.89) and was inversely correlated with rainfall (R = -. 0.88). We linked the post-flush age of each crown's leaf cohort to the Enhanced Vegetation Index (EVI) of crowns at different phenostages on a nadir view QuickBird image. When aggregated to landscape-scale, this camera-based EVI closely followed (R = 0.95) the MODIS MAIAC EVI of the same site, fully corrected for sun-sensor geometry effects. Leaf phenology therefore drives the dry season green-up detected by MODIS in the Central Amazon. It is also consistent with evolutionary strategies to couple photosynthetic efficiency with light availability and to avoid predation and disease on vulnerable young leaves.
KW - Dry season green-up
KW - Enhanced Vegetation Index
KW - Green Chromatic Coordinate
KW - Leaf abscission
KW - Leaf flush
KW - Phenocam
KW - Tropical forest
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U2 - 10.1016/j.rse.2016.05.009
DO - 10.1016/j.rse.2016.05.009
M3 - Article
AN - SCOPUS:84969850503
VL - 182
SP - 90
EP - 98
JO - Remote Sensing of Environment
JF - Remote Sensing of Environment
SN - 0034-4257
ER -