Nations of the world face challenges in developing
sound policies and directions for addressing global change. The
scientific community has the responsibility to provide the scientific
basis for those policies. This includes developing the understanding
of the influence of land, ocean and atmospheric processes in climate
change. The goal of AmeriFlux is to develop a coordinated research
network of long-term flux sites in the Americas for quantifying
and understanding the role of the terrestrial biosphere in global
climate change. Specifically, the network aims to provide reliable
estimates of carbon stocks in plants and soil, biological and environmental
controls on carbon dioxide and water vapor exchange between the
land and atmosphere, and improve our description and understanding
of variation from ecosystems to continents and from seasons to decades.
The network provides quantitative information to adequately predict
large-scale long-term responses to changing environmental conditions.
This is accomplished using micrometeorological and biological measurements
at intensive sites coupled with extensive measurements (e.g. surveys
and remote sensing) and modeling. For ecotype and instrumentation details for all AmeriFlux research sites nationwide, visit the
Key science questions of AmeriFlux are:
- What are the magnitudes of carbon storage
and the exchanges of energy, CO2 and water vapor in terrestrial
systems? What is the spatial and temporal variability?
- How is this variability influenced by vegetation
type, phenology, changes in land use, management, and disturbance
history, and what is the relative effect of these factors?
- What is the causal link between climate and the exchanges
of energy, CO2 and water vapor for major vegetation types,
and how does seasonal and inter-annual climate variability
and anomalies influence fluxes?
- What is the spatial and temporal variation of boundary
layer CO2 concentrations, and how does this vary with topography,
climatic zone and vegetation?
- As of January 2011, the AmeriFlux data archive
contains 787 site-years of data from 140 sites. Of these
140 sites, 92 are still active and 48 are inactive. 90 sites are in the United States, 1 in Brazil,
and 1 in Mexico.
- Across sites, an
average of 83% of the total amount of carbon taken up
by the terrestrial systems in photosynthesis was respired
back to the atmosphere.
- Volcanic aerosols from the 1991 Mt. Pinatubo
eruption greatly increased diffuse radiation worldwide
for the following two years.
- AmeriFlux sites bolster progress towards
verifiable regional carbon cycle flux estimates.
- Validation of the satellite remote sensing
MOD17 algorithm (GPP and NPP) is on-going (Running & Heinsch)
- A preliminary study on how representative
AmeriFlux sites are of the ecoregions in the coterminous
US showed that southern, southwestern, and Pacific Northwest
environments are less well represented by the existing
tower sites (Hargrove et al. 2003). Further analysis will
be conducted over the next three years.
- Integrating flux tower methods with ground-based biometry
reveals the importance of disturbance dynamics in controlling
large-scale carbon balance in the Amazon of Brazil.
- AmeriFlux data were used to demonstrate the importance
of phenology to seasonal and interannual variation in
NEE (Gu et al. 2003b).
- AmeriFlux tower flux data were used to examine the role
of climate on soil C decomposition rates.
- Several studies in seasonally drought affected or well-drained
sites have observed large soil respiration responses to
pulse rain events.
- Flux tower data analysis methods continue to be developed
and explored to produce quality data for synthesis activities
and reduce uncertainty in flux estimates.