Nitrogen Inputs and Losses in Response to Chronic CO₂ Exposure in a Subtropical Oak Woodland

Authors

B. A. Hungate, Northern Arizona University
B. D. Duval, Northern Arizona University
P. Dijkstra, Northern Arizona University
D. W. Johnson, University of Nevada-Reno
M. E. Ketterer, Northern Arizona University
Peter Stiling, University of South FloridaFollow
W. Cheng, Yamagata University
J. Millman, Horace Mann Bronx Campus
A. Hartley, Florida Gulf Coast University
D. B. Stover, Office of Biological and Environmental Research, US Department of Energy

Document Type

Article

Publication Date

6-23-2014

Digital Object Identifier (DOI)

https://doi.org/10.5194/bg-11-3323-2014

Abstract

Rising atmospheric CO₂ concentrations may alter the nitrogen (N) content of ecosystems by changing N inputs and N losses, but responses vary in field experiments, possibly because multiple mechanisms are at play. We measured N fixation and N losses in a subtropical oak woodland exposed to 11 years of elevated atmospheric CO₂ concentrations. We also explored the role of herbivory, carbon limitation, and competition for light or nutrients in shaping the response of N fixation to elevated CO₂. Elevated CO₂ did not significantly alter gaseous N losses, but lower recovery and deeper distribution in the soil of a long-term ¹⁵N tracer indicated that elevated CO₂ increased leaching losses. Elevated CO₂ had no effect on nonsymbiotic N fixation, and had a transient effect on symbiotic N fixation by the dominant legume. Elevated CO₂ tended to reduce soil and plant concentrations of iron, molybdenum, phosphorus, and vanadium, nutrients essential for N fixation. Competition for nutrients and herbivory likely contributed to the declining response of N fixation to elevated CO₂. These results indicate that positive responses of N fixation to elevated CO₂ may be transient and that chronic exposure to elevated CO₂ can increase N leaching. Models that assume increased fixation or reduced N losses with elevated CO₂ may overestimate future N accumulation in the biosphere.

Rights Information

This work is licensed under a Creative Commons Attribution 3.0 License.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Biogeosciences, v. 11, p. 3323-3337

Scholar Commons Citation

Hungate, B. A.; Duval, B. D.; Dijkstra, P.; Johnson, D. W.; Ketterer, M. E.; Stiling, Peter; Cheng, W.; Millman, J.; Hartley, A.; and Stover, D. B., "Nitrogen Inputs and Losses in Response to Chronic CO₂ Exposure in a Subtropical Oak Woodland" (2014). Integrative Biology Faculty and Staff Publications. 318.
https://digitalcommons.usf.edu/bin_facpub/318