,This data package was produced by researchers working on the Shortgrass Steppe Long Term Ecological Research (SGS-LTER) Project, administered at Colorado State University. Long-term datasets and background information (proposals, reports, photographs, etc.) on the SGS-LTER project are contained in a comprehensive project collection within the Digital Collections of Colorado (http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429). The data table and associated metadata document, which is generated in Ecological Metadata Language, may be available through other repositories serving the ecological research community and represent components of the larger SGS-LTER project collection. The belowground system in arid and semiarid regions can be of relatively greater importance than in more mesic systems because plant competition is most often for soil water rather than for light in aboveground canopies. Belowground plant biomass in the shortgrass steppe represents approximately 80% of the total. These data, entitled Long-Term Seasonal Root Biomass, were obtained in section 21 of the Central Plains Experimental Range from 1985-2008 in conjunction with a 14C labeling experiment designed to test isotope methods of estimating root production. Paired plots for each of eight replicate 14C labeled plots were established and cored on average six times per year over 13 years (five cores each plot each date as above). There were two primary objectives for collecting these data, 1) to compare estimates of root production (or belowground net primary production - BNPP) obtained using the sequential coring of biomass methods with various isotope, minirhizotron, ingrowth, and other methods, and 2) to examine long-term controls on the temporal dynamics of root biomass. This shortgrass steppe LTER site is the only place we are aware of that has compared most methods of estimating BNPP, including sequential coring, ingrowth cores, and ingrowth donuts, 14C pulse-isotope dilution, 14C pulse-isotope turnover, rhizotron windows, and minirhizotron, and indirect methods including nitrogen budget, carbon flux, simulation carbon flow model, and regression model. All production methods are compared in Milchunas (2009), and more detailed comparisons among particular methods can be found in Milchunas and Lauenroth (1992, 2001), and Milchunas et al. (2005a, and 2005b). Results and conclusions concerning root biomass dynamics and relationships with precipitation, season, and aboveground biomass are reported primarily in Milchunas and Lauenroth (2001). If you are interested in using these data they are downloadable from the SGS website, however we encourage you to seek advice from the researchers on the SGS project before you apply this dataset. Milchunas D. G., and W. K. Lauenroth. 1992. Carbon dynamics and estimates of primary production by harvest, C14 dilution, and C14 turnover. Ecology 73:593-607. Milchunas, D. G., and W. K. Lauenroth. 2001. Belowground primary production by carbon isotope decay and long-term root biomass dynamics. Ecosystems 4:139-150. Milchunas, D. G., J. A. Morgan, A. R. Mosier, and D. LeCain. 2005a. Root dynamics and demography in shortgrass steppe under elevated CO2, and comments on minirhizotron methodology. Global Change Biology 11:1837-1855. Milchunas, D. G., A. R. Mosier, J. A. Morgan, D. LeCain, J. Y. King, and J. A. Nelson. 2005b. Root production and tissue quality in a shortgrass steppe exposed to elevated CO2: Using a new ingrowth method. Plant and Soil 268:111-122. Milchunas, D. G. 2009. Estimating root production: comparison of 11 methods in shortgrass steppe and review of biases. Ecosystems 12:1381-1402. Additional information and referenced materials can be found: http://hdl.handle.net/10217/85665.,,