AmeriFlux Network Measures Ecosystem Function

Protection of our natural resources in becoming increasingly dependent on careful monitoring, data collection and interpretation of these observations of how our world works.  The AmeriFlux network provides scientific development of methods as well as gathering and analysis of ecosystem data. These scientists quantify and advance understanding of processes regulating carbon assimilation, respiration, and storage, and linkages between carbon, water, energy and nitrogen through measurements and modeling.

The AmeriFlux network includes more than 120 independently funded sites operating across North, Central, and South America. AmeriFlux sites include tundra, grassland, agricultural crops, tropical forests and temperate coniferous and deciduous forests.

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, Ameriflux aims to provide reliable estimates of carbon storage, carbon dioxide and water vapor exchange, and improve our description and understanding of variation, and its causes at relevant temporal and spatial scales. We expect to provide the quantitative information to adequately predict large-scale long-term responses to changing environmental conditions.

This will be accomplished using micrometeorological and biological measurements at the intensive flux sites coupled with extensive measurements (e.g. surveys and remote sensing) and modeling.

The AmeriFlux network was established in 1996. The network provides continuous observations of ecosystem level exchanges of CO₂, water, energy and momentum spanning diurnal, synoptic, seasonal, and interannual time scales and is currently composed of sites from North America, Central America, and South America.

AmeriFlux is part of a "network of regional networks" (FLUXNET) which coordinates regional and global analysis of observations from micrometeorological tower sites. Learn more about FLUXNET and other regional carbon flux networks.

The network role is to address the scientific uncertainties associated with global change. AmeriFlux' focus is to address these scientific questions:

1. 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?


2. 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?


3. 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?


4. What is the spatial and temporal variation of boundary layer CO₂ concentrations, and how does this vary with topography, climatic zone and vegetation?

• Aspirated temperature. The AmeriFlux network needs to ensure temperature measurements are unbiased and stable with time
• Net Radiation. All sites should consistently use aspirators and account for any wind-speed corrections in their radiation measurements.
• Photosynthetic Photon Flux Density (PPFD) and incident radiation.
• Sonic Anemometry. There is no model of sonic anemometer-thermometers (SATs) that is ideal for all situations. Model type should be chosen by the site PI to best suit the site conditions and overall research questions.Scalar density measurements for CO2 and H2O. Precise scalar concentrations are needed to quantify the high frequency turbulent fluctuations of scalar density in making flux measurementsProfile systems. Because any 30-min scalar flux is the sum of both turbulent exchange and the vertical integrated rate of change of the scalar, it is important to have a CO2 profile system particularly at sites that have a developed canopy > 1 m in height.
• Soil respiration. Automated continuous measurements of soil respiration, and accompanying spatial representation with portable chambers, plus soil temperature and moisture profiles should be added to Tier 1 sites, and possibly some Tier 2 sites. We have found that automated chamber measurements of soil respiration (hourly)Water budget components. One key AmeriFlux objective is to explain the processes that control the fluxes of water vapor, and to determine how water vapor flux temporally and spatially affect the exchange of carbon (AmeriFlux Science Plan).
• Reporting calibration records (metadata) and data quality flags (for each 30-min period) in a centralized data repository (i.e., CDIAC) should also be explored to enhance overall network data quality