Amazon rainforests green‐up with sunlight in dry season

Metabolism and phenology of Amazon rainforests significantly influence global dynamics of climate, carbon and water, but remain poorly understood. We analyzed Amazon vegetation phenology at multiple scales with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite measurements from 2000 to 2005. MODIS Enhanced Vegetation Index (EVI, an index of canopy photosynthetic capacity) increased by 25% with sunlight during the dry season across Amazon forests, opposite to ecosystem model predictions that water limitation should cause dry season declines in forest canopy photosynthesis. In contrast to intact forests, areas converted to pasture showed dry‐season declines in EVI‐derived photosynthetic capacity, presumably because removal of deep‐rooted forest trees reduced access to deep soil water. Local canopy photosynthesis measured from eddy flux towers in both a rainforest and forest conversion site confirm our interpretation of satellite data, and suggest that basin‐wide carbon fluxes can be constrained by integrating remote sensing and local flux measurements.

[1]  P. Sellers.  Canopy reflectance, photosynthesis and transpiration , 1985 .

[2]  C. Field,et al.  A reanalysis using improved leaf models and a new canopy integration scheme , 1992 .

[3]  Carel P. van Schaik,et al.  Light and the Phenology of Tropical Trees , 1994, The American Naturalist.

[4]  E. Davidson,et al.  The role of deep roots in the hydrological and carbon cycles of Amazonian forests and pastures , 1994, Nature.

[5]  Ranga B. Myneni,et al.  The interpretation of spectral vegetation indexes , 1995, IEEE Transactions on Geoscience and Remote Sensing.

[6]  H. Tian,et al.  Effect of interannual climate variability on carbon storage in Amazonian ecosystems , 1998, Nature.

[7]  Alan H. Strahler,et al.  The Moderate Resolution Imaging Spectroradiometer (MODIS): land remote sensing for global change research , 1998, IEEE Trans. Geosci. Remote. Sens..

[8]  D. Roberts,et al.  Spectral changes with leaf aging in Amazon caatinga , 1998, Trees.

[9]  Yadvinder Malhi,et al.  Carbon dioxide transfer over a Central Amazonian rain forest , 1998 .

[10]  A. Huete,et al.  Optical-Biophysical Relationships of Vegetation Spectra without Background Contamination , 2000 .

[11]  G. Asner,et al.  Satellite observation of El Niño effects on Amazon Forest phenology and productivity , 2000 .

[12]  W. Sombroek.  Spatial and Temporal Patterns of Amazon Rainfall , 2001 .

[13]  W. Sombroek,et al.  Spatial and temporal patterns of Amazon rainfall. Consequences for the planning of agricultural occupation and the protection of primary forests. , 2001, Ambio.

[14]  W. Sombroek,et al.  Spatial and Temporal Patterns of Amazon Rainfall , 2001 .

[15]  G. Vourlitis,et al.  Seasonal variations in the net ecosystem CO2 exchange of a mature Amazonian transitional tropical forest (cerradão) , 2001 .

[16]  Eric A. Davidson,et al.  The effects of partial throughfall exclusion on canopy processes, aboveground production, and biogeochemistry of an Amazon forest , 2002 .

[17]  Yadvinder Malhi,et al.  Seasonality in CO2 and H2O flux at an eastern Amazonian rain forest , 2002 .

[18]  A. Huete,et al.  Overview of the radiometric and biophysical performance of the MODIS vegetation indices , 2002 .

[19]  N. Ramankutty,et al.  Long‐term variations of climate and carbon fluxes over the Amazon basin , 2002 .

[20]  M. Keller,et al.  Carbon in Amazon Forests: Unexpected Seasonal Fluxes and Disturbance-Induced Losses , 2003, Science.

[21]  C. Tucker,et al.  Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999 , 2003, Science.

[22]  G. Asner,et al.  Drought stress and carbon uptake in an Amazon forest measured with spaceborne imaging spectroscopy. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[23]  Scott D. Miller,et al.  DIEL AND SEASONAL PATTERNS OF TROPICAL FOREST CO2 EXCHANGE , 2004 .

[24]  Osvaldo L. L. Moraes,et al.  Land‐use change effects on local energy, water, and carbon balances in an Amazonian agricultural field , 2004 .

[25]  M. Hodnett,et al.  Comparative measurements and seasonal variations in energy and carbon exchange over forest and pasture in South West Amazonia , 2004 .

[26]  Scott D. Miller,et al.  SEASONALITY OF WATER AND HEAT FLUXES OVER A TROPICAL FOREST IN EASTERN AMAZONIA , 2004 .

[27]  Michael W. Palace,et al.  CARBON BALANCE AND VEGETATION DYNAMICS IN AN OLD-GROWTH AMAZONIAN FOREST , 2004 .

[28]  G. Vourlitis,et al.  Ecological research in the large-scale biosphere-atmosphere experiment in Amazonia: early results , 2004 .

[29]  S. Frolking,et al.  Satellite-based modeling of gross primary production in a seasonally moist tropical evergreen forest , 2005 .

[30]  Hideki Kobayashi,et al.  Atmospheric conditions for monitoring the long-term vegetation dynamics in the Amazon using normalized difference vegetation index , 2005 .

[31]  D. Sims,et al.  Potential of MODIS EVI and surface temperature for directly estimating per‐pixel ecosystem C fluxes , 2005 .

[32]  Stephen S. O. Burgess,et al.  Hydraulic redistribution in three Amazonian trees , 2005, Oecologia.

[33]  H. G. Baker,et al.  SOIL AND STEM WATER STORAGE DETERMINE PHENOLOGY AND DISTRIBUTION OF TROPICAL DRY FOREST TREES ' , 2007 .