Recommended core and desired Meteorological and Flux Measurements to be carried out at each AmeriFlux site. X's indicate aspects measured in the CARBONO project.

I. EDDY FLUX DENSITIES

A. CORE MEASUREMENTS
X 1. sensible heat
X 2. latent heat (evapotranspiration)
X 3. CO2
X 4. momentum

II. STORAGE FLUXES

A. CORE MEASUREMENTS
X 1. CO2 storage in canopy air layer (CO2 profile)

B. DESIRED MEASUREMENTS
X 1. heat storage in canopy air (temperature profile)

III. SOIL FLUXES

A. CORE MEASUREMENTS
X 1. CO2 flux
X 2. heat flux

B. DESIRED MEASUREMENTS
X 1. water vapor flux

IV. METEOROLOGY

A. CORE MEASUREMENTS
X 1. air temperature (ventilated shielded)
X 2. net radiation
X 3. global radiation or photosynthetically active photon flux density (PPFD)
X 4. RH, or dewpoint temperature or wet bulb temperature
X 5. precipitation
X 6. wind speed and direction

B. DESIRED MEASUREMENTS
X 1. diffuse radiation or PPFD
X 2. absorbed PPFD
X 3. longwave radiation
X 4. canopy wetness
X 5. pressure

Recommended core and desired environmental, soil and biological measurements for forested ecosystems for data interpretation and model execution and testing and application (adopted by the AmeriFlux Science team on the recommendation of the Ecological Measurements Subcommittee of the Science Team, Oct. 29-30, 1997, St. Louis, MO; contributors to this list were: Jiquan Chen, Ken Clark, Peter Curtis, Henry Gholz, Dave Hollinger, RayHunt, Hank Loescher, Ram Oren, and Jess Parker.). A similar list for grassland and crop systems has yet to be finalized although a tentative list is included.

Statement of the Committee The overall objectives of making these measurements are to facilitate among-site comparison and to provide biological process-level interpretation to the eddy covariance flux measurements. Matching ecological measurements with parameterization needs of forest carbon and nutrient flux models is important for both these objectives.

This list is divided into three sections: stand characteristics, stand physiology, and soil characteristics. Within each section we enumerate 'Core' and 'Desired' measurements. Following each measurement is the suggested frequency of collection and occasionally additional notes in brackets. For the most part, no mention is made regarding methods. We have attempted to keep this list as short as possible, recognizing that not all sites are appropriately staffed or funded to carry out extensive ecophysiological studies. However, we feel very strongly that a core set of ecological measurements is critical to the success of the Ameriflux network.

FORESTED ECOSYSTEMS

I. STAND CHARACTERISTICS

A. CORE MEASUREMENTS
X 1. Species composition: single
X 2. Aboveground biomass: single, {basal area, sapwood area, stem density; by species}
X 3. Root biomass: single, {soil cores}
X 4. Canopy height: single
X 5. Maximum leaf area index: annual, {direct - annual litterfall and/or indirect - IPAR}
X a) Seasonal change in canopy LAI: annual
X b) Understory LAI: annual
X 6. Max IPAR: annual.
X 7. Seasonal litterfall: annual
X 8. Site history: single
9. Atmospheric N deposition: annual

B. DESIRED MEASUREMENTS
X 1. LAI profile: single
2. Ground (soil and litter) albedo and canopy albedo: single
X 3. High resolution, muti-spectral satellite image: annual
X 4. Aerodynamic roughness length and zero plane distribution: single

II. STAND PHYSIOLOGY

A. CORE MEASUREMENTS
X 1. Annual aboveground growth increment: annual
X 2. Bole temperature: repeated
X 3. Leaf total nitrogen and carbon content: repeated
X a) Specific leaf area: repeated
b) Total woody tissue and sapwood nitrogen and carbon content: annual

B. DESIRED MEASUREMENTS
1. Stomatal conductance: repeated {max, leaf water potential or VPD at closure}
a) Minimum spring leaf water potential
X b) Sap flow: repeated
2. Annual below ground growth increment: repeated {in-growth cores, minirhizotron tubes}
X 3. Leaf photosynthesis: repeated
a) light response curves: annual {Ic, Amax}
b) A/Ci curves: annual
X 4. Foliar and bole respiration: repeated
5. Leaf and woody tissue total non-structural carbohydrate content: repeated
X a) Tissue 13C/12C ratio: annual
X b) Atmospheric 13C/12C ratio: repeated

III. SOIL CHARACTERISTICS

A. CORE MEASUREMENTS
X 1. Soil temperature profiles: repeated
X 2. Soil moisture: repeated {content, capacity}
X 3. Soil bulk density and porosity: single
X a) soil texture (clay, sand, silt): single
X b) root depth: single
X 4. Soil CO2 flux: repeated
5. litter decomposition rate: annual {bags}

B. DESIRED MEASUREMENTS
X 1. Litter carbon, nitrogen, lignin: single
X 2. Soil carbon and nitrogen: single
3. Nitrogen mineralization rate: single
4. Soil thermal and hydraulic conductivities: single
X 5. Cation exchange capacity: single