EUROFLUX WORKPACKAGES

All the sites will be equipped with a standard equipment for eddy covariance measurements of carbon dioxide, water vapour, sensible heat and momentum fluxes. The standard system consists of the 3D sonic anemometer and a closed path CO2/H2O analyzer. Fluxes are collected every 30 min. and stored. Data will be collected on a continuous basis all year for the duration of the project. Calibration of the analyzer will be carried out at least every 15 days and for some sites the calibration will be automatically performed on a daily basis. In each of the study sites energy balance determination will be carried out. Net radiation will be measured by net radiometers, soil heat flux with a combination of soil heat flux plates and soil temperatures and canopy heat storage by the measurement of vertical temperature profiles. These data will be collected at the same rate as fluxes (30 min) continuously for the duration of the project and will contribute to the project data base.

Two independent tests will be carried out to check the validity of eddy flux data: energy balance closure and spectral analysis. Spectral analysis will be conducted on vertical wind speed, CO2, H2O and temperature data in order to evaluate any deviation from theoretical predictions in the inertial sublayer. In addition a boundary layer analysis will be conducted during night time conditions, to check the response of the eddy covariance system under high atmospheric stability. Eddy flux measurements will be related to the specific source area responsible for them. This analysis will be carried out using the modern concept of "footprint" to determine the source or sink area of a scalar quantity. This technique will be used at each of the sites to relate continuous flux measurements with the spatial distribution of the source areas and thereby, to the ecosystem structural components responsible for these (LAI, biomass, species, etc.).

Group of interest:
Coordinator: J. Moncrieff
Names: P. Berbigier, Shurpali, M. Aubinet, T.Vesala, A. Grelle, J.A. Elbers, Hummelshoj, Bernhofer, Rebman, O.Jensen

Short campaigns will be carried out in order to provide measurements of carbon and oxygen isotopic composition of the air within and above the canopy on a seasonal basis to determine isotopic fluxes. For the determination of isotopic fluxes, two techniques will be used, concentration gradient and eddy accumulation.

Group of interest:
Coordinator: E. Brugnoli
Names: P. Jarvis, B. Kruijt, E-D.Schulze, Guelle

In order to provide basic informations on the carbon distribution within the ecosystem and its changing in time, measurements of biomass components will be carried out in all the sites. Leaf Area Index (LAI) will be estimated both by light interception and direct sampling. Wood increment will be estimated by core sampling at the end of the season and by dendrometer during the vegetation period. Root biomass will be quantified by sampling soil cores during the season and by ingrowth enclosures.

Group of interest:
Coordinator: P. Jarvis
Names: R. Ceulemans, Cermak, A.Granier, Tenhunen, Moren, Loustau, G.Matteucci, M. De Lillis, F. Manes

Soil carbon dioxide fluxes will be estimated by cuvette measurements. Intercomparison exercises are planned in order to evaluate the system performances of each group and to provide a common background for soil respiration measurements. Soil temperatures and soil moistures will be measured in parallel in order to provide functional relationships between climatic factors and fluxes. It will be possible for some sites to have simultaneous measurements of soil CO2 fluxes by eddy covariance during short campaigns. Eddy fluxes will be used to test local derived area integrated cuvettes estimates. Stem and branch respiration will be estimated by cuvettes on selected trees, with the same time schedule of soil respiration. Trees will be selected to be representative of the stand according to diameter distribution, age and species . Leaf level respiration will be measured by portable gas exchgange system during field campaigns and these measurements will be correlated with leaf position within the canopy and other variables, like nutrient status and photosynthetic capacity.

Group of interest:
Coordinator: Lindroth
Names: P. Jarvis, Jaussens, H. Thorgeirsson, Pilegaadr, D.Schulze, Tenhunen, S.Dore

Light interception of the canopy will be measured along the season at different depths. Measurements will be also conducted on leaf level photosynthetic characteristics, leafes nutrient distribution and isotopic composition along a vertical gradient within the canopy. Soil nutrients will be investigated to provide a basic information of the fertility and production potentials of the sites.

Group of interest:
Coordinator: E-D. Schulze
Names: P. Jarvis, D. De Pury

Water inputs will be measured by rainfall gauges and in some sites it will be possible to measure throughfall and stemflow along the season. Soil moisture changes will be followed during the season at each site with a combination of different techniques (soil tensiometers, neutron probe and time domain refractometry). The hydraulic characteristics of the soils will be determined at each site in order to relate soil moisture with matrix potential. Predawn water potentials of small twigs of the trees will be measured along the season using a pressure chamber.

Tree level transpiration studies

Tree transpiration will be measured to provide additional validation potential at selected sites with thermal flowmeters constructed according to dr. Granier and also with the system designed by dr. Cermak, which has been improved by the Bayreuth team. In addition, tree crown conductances will be calculated by sap flow and water potential gradients. The crown conductances will then scaled up at canopy level and compared with canopy conductances determined by eddy fluxes.

Group of interest:
Coordinator: A.Granier
Names: Moors, C.Bernhofer, J. Tenhunen, P. Jarvis, J. Cermak, Cienciala, G. Tirone

Already existing models will be parametrized for a number of sites in order to achieve the following objectives :
1. develop a tool for filling gaps in the long term data series
2. validate model outputs with real flux data.
In particular the following SVAT models will be used: MAESTRO, CANOAK, GAS-FLUX and STANDFLUX.

Group of interest:
Coordinator: J. Tenhunen
Names: P. Martin, A.J. Dolman, P. Jarvis, N.O. Jensen, H. Thorgeirsson, Loustau

During the experimental activity a flow of data will be established between the participating teams in order to create a common data base. At the end of the project a unique set of data of continuous fluxes of various European forests will be available to the external community. Data will be available to the external community after 8 months from the end of the project in the form of CD-ROMs and INTERNET access, providing referencing as European programme EUROFLUX product and citing the principal investigators. Scaling the individual test sites to a European dimension will be carried out mainly bydr. P. Martin and dr. R. Valentini, using regional scale models, like EMU.

Group of interest:
Coordinator: P. Martin
Names: M. Sciortino, R. Valentini, S. Greco, A.Ciaccia

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