The US/IBP Grassland Biome program was one of the largest and most ambitious of the biome-based sub-programs under the Analysis of Ecosystems Project funded by the US National Science Foundation (the others included tundra, deserts, coniferous forests and deciduous forests). It was organised around a central study site and management office, with the aim of studying the whole US grassland system, particularly the seasonal biomass and energy dynamics of grasslands across multiple trophic levels (Sims et al., 1978). The ten sites for which net primary productivity (NPP) data are reported encompass six major grassland types across the central and western United States, ranging from latitude 30 to 48 N and longitude 96 to 123 W, and from 390 m to 2340 m in elevation. Mean annual precipitation ranged from 228 mm to 930 mm, and mean annual temperature from 2.7 C to 15.2 C.
Co-ordinated measurements commenced in the 1970 growing season, and continued until the end of 1972 at most sites, with some additional measurements made in 1973 and 1974. A number of peer-reviewed publications came out in the late 1970s, but much of the ecosystem modelling work originally proposed did not take place due to shortage of funds and time. However, the central office of the Grassland Biome, the Grasslands Laboratory at Colorado State University (CSU), metamorphosed into the Natural Resource Ecology Laboratory at CSU, a leading institution in ecological modelling.
The US/IBP Grasslands Biome has yielded a valuable data collection representing diverse sites at which above-ground and below-ground productivity were measured using comparable methods. Apart from the data available here on biomass dynamics and NPP, an enormous wealth of other measurements was collected on insects, birds and other primary and secondary consumers. The objectives of this and other components of the IBP were indeed far-reaching and ahead of their time (particularly with regard to the proposed use of data for ecosystem simulation modelling), and it is regrettable that much of these data reside only in IBP Technical Reports of limited distribution. The NPP data presented here have been retrieved under the NASA-sponsored component of the Global Primary Production Data Initiative. Through the medium of the World-Wide Web, the recent availability of at least some of these historical scientific data and others to the global ecosystem modelling community should ensure that the results of this impressively co-ordinated research programme receive the attention they deserve.
Summary tables are available, listed below, containing estimates of NPP for above-ground and below-ground compartments, for the US/IBP Grassland Biome sites. ANPP estimates are shown as reported in the original literature, and also as calculated using a range of NPP algorithms (1980s data from Konza Prairie have been included for comparison).