Global compilation of fine-root nutrient concentrations and root diameter

Fine roots are an important source and sink for nutrients in terrestrial ecosystems. Given the relatively short life-spans of fine roots, understanding the relationship between fine root diameter and nutrient contents, and the extent to which nutrients are retranslocated prior to turnover, is important for estimating nutrient cycling in terrestrial ecosystems. To study patterns of nutrient concentrations in fine roots, we examined published accounts for roots [less than or equal] mm in diameter, building on the database of Jackson et al. (1996, 1997). The synthesized studies included data from a range of ecosystems and biomes, including grass, shrub, and tree functional types from temperate, tropical, boreal, and tundra systems. The preponderance of data came 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 plantations. Data from fertilized systems were excluded, as were results from pot or greenhouse experiments and studies with seedlings. Criteria for inclusion were that each study provide information on root status (i.e., live, dead, or undifferentiated) and that if a range of root sizes were reported (e.g., 1-3 mm, 3-5 mm) the reported range did not exceed 2.5 mm. For information on the 56 studies used for the database and the spreadsheet used in the calculations see the Appendix. References: (1) 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. (2) 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, USA 94:7362-7366.