Interactive effects of time, CO2, N, and diversity on total belowground carbon allocation and ecosystem carbon storage in a grassland community

E. Carol Adair, Peter B. Reich, Sarah E. Hobbie, Johannes M.H. Knops

Research output: Contribution to journalArticlepeer-review

97 Scopus citations


Predicting if ecosystems will mitigate or exacerbate rising CO2 requires understanding how elevated CO2 will interact with coincident changes in diversity and nitrogen (N) availability to affect ecosystem carbon (C) storage. Yet achieving such understanding has been hampered by the difficulty of quantifying belowground C pools and fluxes. Thus, we used mass balance calculations to quantify the effects of diversity, CO2, and N on both the total amount of C allocated belowground by plants (total belowground C allocation, TBCA) and ecosystem C storage in a periodically burned, 8-year Minnesota grassland biodiversity, CO2, and N experiment (BioCON). Annual TBCA increased in response to elevated CO 2, enriched N, and increasing diversity. TBCA was positively related to standing root biomass. After removing the influence of root biomass, the effect of elevated CO2 remained positive, suggesting additional drivers of TBCA apart from those that maintain high root biomass. Removing root biomass effects resulted in the effects of N and diversity becoming neutral or negative (depending on year), suggesting that the positive effects of diversity and N on TBCA were related to treatment-driven differences in root biomass. Greater litter production in high diversity, elevated CO2, and enhanced N treatments increased annual ecosystem C loss in fire years and C gain in non-fire years, resulting in overall neutral C storage rates. Our results suggest that frequently burned grasslands are unlikely to exhibit enhanced C sequestration with increasing atmospheric CO2 levels or N deposition.

Original languageEnglish (US)
Pages (from-to)1037-1052
Number of pages16
Issue number6
StatePublished - Sep 2009

Bibliographical note

Funding Information:
We thank the undergraduate BioCON interns for field and lab work and Jared Trost and Dan Bahauddin for experimental maintenance and data acquisition and management. This research was supported by NSF Grants DEB-0322057, DEB-0080382, DEB-0218039, DEB-0219104, DEB-0217631 (BioComplexity and Cedar Creek Long-Term Ecological Research projects).


  • Belowground carbon flux
  • BioCON
  • Carbon budget
  • Carbon cycling
  • Cedar Creek LTER
  • Elevated CO
  • FACE experiment
  • Nitrogen deposition
  • Species richness


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