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Title: Redefining fine roots improves understanding of belowground contributions to terrestrial biosphere processes

Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain due to challenges in consistent measurement and interpretation of fine-root systems. We define fine roots as all roots less than or equal to 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. We demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, fine roots are separated into either individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine root pool. Furthermore, using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally a ca. 30% reduction from previous estimates assuming a single fine-root pool. In the future we hope to develop tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi in fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand belowground processes in the terrestrial biosphere.
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [6] ;  [7] ;  [8] ;  [9] ;  [6] ;  [8] ;  [10] ;  [11] ;  [12] ;  [13] ;  [14]
  1. Chinese Academy of Sciences, Beijing (China)
  2. Lincoln Univ., Canterbury (New Zealand)
  3. Pennsylvania State Univ., University Park, PA (United States)
  4. Cornell Univ., Ithaca, NY (United States)
  5. Univ. of Minnesota, St. Paul, MN (United States)
  6. Univ. of Helsinki, Helsinki (Finland)
  7. Univ. of New Hampshire, Durham, NH (United States)
  8. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  9. Stanford Univ., Stanford, CA (United States)
  10. Indiana Univ., Bloomington, IN (United States)
  11. Univ. of Idaho, Moscow, ID (United States)
  12. College of Charleston, Charleston, SC (United States)
  13. Univ. of Natural Resources and Life Sciences, Vienna (Austria)
  14. Polish Academy of Sciences, Kornik (Poland)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC05-00OR22725; 31350110503
Accepted Manuscript
Journal Name:
New Phytologist
Additional Journal Information:
Journal Volume: 207; Journal Issue: 3; Journal ID: ISSN 0028-646X
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
58 GEOSCIENCES ecosystem; plant traits; net primary productivity (NPP); belowground; mycorrhizal fungi; ecosystem modeling; plant allocation; fine-root order