The variability of net surface carbon assimilation (Asmax), net ecosystem surface respiration (Rsmax), and net surface evapotranspiration (Etsmax) among and within vegetation types was examined on the basis of a review of studies performed in either a micrometeorological setting or an enclosure setting. The majority of studies involved forests and C3 crops, particularly in the northern hemisphere; however, studies on tropical forests, C4 grasslands or wetlands were included. Data are presented for 133 published studies, although individual studies may not have measure all variables of interest.
Despite large variations within a vegetation type, enclosure studies tended to give highest Asmax rates in comparison with studies using micrometeorological techniques (Buchmann and Schulze 1999). Excluding enclosure studies, the investigators tested the effect of stand age and leaf area index (LAI) on net ecosystem gas exchange. The results from these analyses illustrate where gaps in scientific knowledge exist and how ecosystem properties affect the capacity of net ecosystem gas exchange.
The information was collected from papers with publication dates from 1969 to 1998. Mean maximum flux rates for the period chosen by the authors were used instead of absolute maximum values for flux rates. Positive values stand for CO 2 uptake by the vegetation and negative values represent CO 2 release from the ecosystem. More information about the compilation can be found in Buchmann and Schultze (1999) or the individual studies cited in the data table.
Cite this data set as follows:
Buchmann, N., and E.-D. Schulze. 2003. Net Carbon Dioxide and Water Fluxes of Global Terrestrial Ecosystems, 1969-1998. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/662.
Buchmann, N., and E.-D. Schulze. Net CO 2 and H 2O fluxes of terrestrial ecosystems. 1999. Global Biogeochemical Cycles 13:3:751-760.
The Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) for Biogeochemistry Dynamics organized and formatted these data for long-term archive.
The data file of 133 study sites includes 110 micrometeorological studies and 23 enclosure studies. The type of study (micrometeorological or enclosure) and classification of the ecosystem given by Buchmann were added to each entry. Also, for the geographic coordinates, S and W directions were given negative values, and N and E were given positive values.
The geographic coordinates given in the list should be used with caution because of inconsistency in reporting. The values appear to be decimal degrees, but it appears that sometimes the minutes of the location were rounded and used as the decimal part of the coordinate; i.e., coordinates for the Tennessee site are 35.6° N and 84.2° W. The most probable corresponding site in the FLUXNET network is Walker Branch Watershed, which has coordinates of 35° 57' 31.56 N and 84° 17' 14.76 W and the more precise decimal degrees of 35.9587 and –84.2874.
Data file of CO2 and H2O Fluxes
net_co2_h2o_table.csv or net_co2_h2o_table.txt: (ASCII tab-delimited file). Missing values set to -9999.
Variables Description Study_Type Type of study Classification Ecosystem: Broad-leaved forests, C3 crops, C3 grasslands, C3/C4 savanna, C4 crops, C4 grasslands, Coniferous forests, Salt marsh, Tropical forests, or Tundra Vegetation Vegetation type or area e.g. picea sitkosis, pinus sylvestris, bog fen, etc. Location Country and/or city Latitude Latitude (please see caution in Data Format description) Longitude Longitude (please see caution in Data Format description) LAI_max Maximum canopy leaf area index (LAI) Height Maximum canopy height [m] Age Stand age [years] Time Time of year Asmax Net maximum surface assimilation of carbon [mmol] [m^-2] [s^-1] Rsmax Net maximum ecosystem respiration of carbon [mmol] [m^-2] [s^-1] Gsmax Ecosystem surface conductance values [mm] [s^-1] Etsmax Net maximum daytime evapotranspiration [mm] [d^-1] Reference Numbered reference that can be found in the companion reference file. Stars (*) denote unpublished data or manuscript in preparation at time of publication (1999).
Companion Reference File for Data
net_co2_h2o_references.txt: (also .pdf and .rtf formats)
Text file with references cross-referenced by citation number to data file.
April 8, 2003
April 8, 2003