(a) AmeriFlux tower

The AmeriFlux network, established in 1996, includes more than 40 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. AmeriFlux sites are an infrastructure for making long-term measurements CO2, water, and energy exchanges from a variety of ecosystems. These data have provided a wealth of information on how diverse ecosystems respond to changes in their physical environment, and how they affect their environments in turn. Contributions to carbon cycle science include understanding variation in net carbon uptake with interannual variation in climate, and the influence of disturbance on carbon storage and fluxes.

(b) Free Air CO2 Enrichment (FACE)

Reducing uncertainties in estimates of atmospheric CO2 and carbon sequestration requires narrowing errors in estimates of present and future biosphere-atmosphere CO2 gross fluxes. FACE facilities can tell us how increasing atmospheric CO2 will change terrestrial ecosystem behavior. FACE provides a technology by which the microclimate around growing plants may be modified to simulate climate change conditions. Typically, CO2-enriched air is released from a circle of vertical pipes into plots up to 30 m in diameter, and as tall as 20 m. FACE field data represent plant and ecosystem responses to concentrations of atmospheric CO2 expected in the mid-21st century.

Credit: FACE -- Brookhaven National Laboratory

(c) Elevated CO2 concentration experiment

The Smithsonian Environmental Research Center (SERC) is conducting a series of innovative experiments that expose portions of salt marsh and forest ecosystems to elevated CO2 concentrations in outdoor chambers. SERC has established two sites for studying the impacts of elevated CO2 on plants and ecosystem processes: a wetland study on Chesapeake Bay and a scrub oak site on Merritt Island Wildlife Refuge, Cape Canaveral, Florida.