Terrestrial net primary productivity (NPP) estimates are compiled from the literature for 34 grasslands, 14 tropical forest sites, and 5 boreal forest sites.
The terrestrial net primary productivity (NPP) database at the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) (
Criteria for selecting intensive study sites included the availability of complete and consistent information on NPP or at least partial NPP(components such as litterfall or biomass increment), together with biomass (standing crop of live matter). Site-description metadata, such as latitude, longitude, and elevation, were considered essential for linking the data to model-driving climate variables (which may be interpolated from actual measurement stations to the NPP study sites). Information on vegetation type (biome), soil type, and land-use history was also a prerequisite for inclusion of a study site in the compilation.
Quality assurance included cross-checking the NPP records against other compilations of NPP data, eliminating duplicates or documenting multiple treatments at one study site, mapping the points in geographical space to confirm they coincided with the landforms, and checking data ranges for outlying values. The NPP data were provided or discovered in a variety of forms, ranging from tabulated computer text files to graphs from publications or theses. In addition, we communicated with the original authors, or their successors, to ascertain their interest and to seek additional information, data updates and corrections, and permissions.
In common with many types of ecological and environmental data, our criteria for consistency included the use of common systems of names (e.g., species, vegetation classes), units of measure, and place names conversion or translation was needed in many cases.
Mean annual average temperature and total precipitation were compiled from the literature source containing the NPP data, when available.
Scurlock et al. (2002) examined various methods for estimating NPP from grassland biomass measurements for 31 sites. While that analysis demonstrated a potential bias of NPP estimates depending on which method was used, the grassland NPP estimates presented here rely primarily on the published estimates of NPP.
References for the source of individual site data and NPP estimates for specific years, biomass, climate, and other associated environmental variables for the 53 detailed study sites are available on the ORNL DAAC NPP Web site (http://www.daac.ornl.gov/NPP/npp_home.html) .
Scurlock, J. M. O., and R. J. Olson. 2003. NPP Multi-Biome: Grassland, Boreal Forest, and Tropical Forest Sites, 1939-1996. 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.
Scurlock, J. M. O., K. Johnson, and R. J. Olson. 2002. Estimating net primary production from worldwide extant grassland biomass dynamics measurements. Global Change Biology8:736-748.
Olson, R. J., K. Johnson, D. Zheng, and J. M. O. Scurlock. 2001. Global and Regional Ecosystem Modeling: Databases of Model Drivers and Validation Measurements.ORNL/TM-2001/196. Oak Ridge National Laboratory, Oak Ridge, Tennessee.
The following variables are included in the summary NPP data file from Scurlock and Olson (2002) Appendix A, Table A.1 with additional columns:
February 4, 2003
Document Review Date:
February 4, 2003