Interactive Effects of Time, CO₂, N, and Diversity on Total Belowground Carbon Allocation and Ecosystem Carbon Storage in a Grassland Community

• Published in: Ecosystems (New York) Vol. 12; no. 6; pp. 1037 - 1052
• Main Authors: Carol Adair, E, Reich, Peter B, Hobbie, Sarah E, Knops, Johannes M. H
• Format: Journal Article
• Language: English
• Published: New York New York : Springer-Verlag 01.09.2009; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Carbon dioxide; Ecology; Environmental Management; Fundamental and applied biological sciences. Psychology; General aspects; Geoecology/Natural Processes; Grasslands; Hydrology/Water Resources; Life Sciences; Nitrogen; Plant Sciences; Predictions; Synecology; Zoology; carbon cycling; BioCON; species richness; belowground carbon flux; Cedar Creek LTER; carbon budget; nitrogen deposition; FACE experiment; elevated CO; Grassland; Atmospheric fallout; Carbon dioxide; Diversity; Increase; Nitrogen; Carbon; Carbon cycle; Medium enrichment; Storage; Ecosystem; Community; Species richness
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-009-9278-9

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 CO₂, 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.