DOI: 10.5063/aa/nceas.198.1
title: Global Distribution of Root Nutrient Concentrations in Terrestrial Ecosystems

description: Nutrient measurements for fine roots were compiled from 56 published studies providing information on 372 different combinations of species, root diameter, rooting depths, and soils at a variety of locations. The compilation was used to examine dynamics of 14 nutrients, including translocation properties of roots of varying size and status. Fine roots are an important source and sink for nutrients in terrestrial biogeochemistry. The data collected come from 56 published studies that give information on fine root (less than 5-mm diameter) nutrient concentrations, root diameters, and retranslocation of nutrients. These studies include diverse vegetation and biomes, including grass, shrub, and tree functional types from temperate, tropical, boreal and tundra systems. The preponderance of data comes from experiments with temperate and coniferous trees. Study sites were a mixture of natural and manipulated ecosystems, including old growth, secondary growth, old fields, and tundra systems. Data from fertilized, potted or greenhouse experiments were excluded. Data are available by diameter class. This listing builds on the database of Jackson et al (1996, 1997) (Jackson, R. B., H. A. Mooney, and E.-D. Schulze. 1997. A global budget for fine root biomass, surface area, and nutrient contents. Proceedings of the National Academy of Sciences, U.S.A. 94:7362-7366.; Jackson, R. B., J. Canadell, J. R. Ehleringer, H. A. Mooney, O. E. Sala, and E.-D. Schulze. 1996. A global analysis of root distributions for terrestrial biomes. Oecologia 108:389-411). Please see Gordon and Jackson (2000) for more information (Gordon, W. S., and R. B. Jackson. 2000. Nutrient concentrations in fine roots. Ecology 81:1:275-280). The following hypotheses were examined (Gordon and Jackson 2000) for fine root nutrients by analyzing these data: (1) that there is an inverse relationship of fine root nutrient concentrations with root diameter, and (2) that retranslocation of nutrients out of fine roots is minimal. Nutrient concentrations of roots less than or equal to 5 mm in diameter were analyzed as a function of root diameter and root status (live, dead, and undifferentiated), including a comparison for coniferous and broad-leaved trees. From the results, mean N concentrations in live and dead fine roots were identical and may imply little retranslocation of root N with senescence, but conflicting evidence from C:N ratios highlights the need for further research (Gordon and Jackson 2000). These results have practical implications for various ecological methods and for the representation of roots in biogeochemical models. A PDF copy of the Gordon and Jackson (2000) paper is available at http://www.biology.duke.edu/jackson/Ecol99.htm. This data set builds on the initial root data compiled by R. B. Jackson in the mid-1990s (see Jackson et al. 1996; Jackson et al. 1997). The expanded and updated data set (Gordon and Jackson 2000) contains nutrient concentrations for approximately 372 site-pit-depths from 56 papers. In addition, the initial Jackson data set has been expanded for studies with root turnover rates (data for 341 site-vegetation combinations for approximately 188 sites from 152 papers in Gill and Jackson 2000: Gill, R., and R. B. Jackson. 2000. Global patterns of root turnover for terrestrial ecosystems. New Phytologist 81:275-280) and rooting depth (data for approximately 298 sites with 565 profiles in Schenk and Jackson 2002: Schenk, H. J., and R. B. Jackson. 2002. The global biogeography of roots. Ecological Monographs 72(3):311-328). The three recent papers include most of the data contained in the initial root data set; however, some observations may have been excluded because of more stringent selection criteria. Many of the source papers provided data for the three recent rooting papers and users are encouraged to review all three data sets.