Plant and Soil Mediation of Elevated CO2 Impacts on Trace Metals
- 253 Downloads
The cycling of trace metals through terrestrial ecosystems is modulated by plant and soil processes. Changes in plant growth and function and soil properties associated with increased atmospheric carbon dioxide (CO2) may therefore also affect the biological storage and stoichiometry of trace metals. We examined CO2 effects on a suite of metal micronutrients and contaminants in forest trees and soils at two free-air CO2 enrichment sites—a loblolly pine forest in North Carolina (Duke) and a sweetgum plantation in Tennessee [Oak Ridge National Laboratory (ORNL)]—and an open-top chamber experiment in a scrub-oak community in Florida [Smithsonian Environmental Research Center (SERC)]. We found that CO2 effects on soil metals were variable across sites; there were significantly higher surface soil metal concentrations with CO2 enrichment at Duke and ORNL (P < 0.05), but a trend of decreased soil metal concentrations at SERC (non-significant). These impacts on metals may be understood in the context of CO2 effects on soil organic matter (SOM); changes in percent SOM with CO2 enrichment were greatest at Duke (18% increase), followed by ORNL (7% increase), with limited effect at SERC (3% increase). There were significant effects of elevated CO2 on foliar metal concentrations at all sites, but the response of foliar metals to CO2 enrichment varied by metal, among sites, and within sites based on plant species, canopy height, and leaf age. Contrary to expectations, we did not find an overall decline in foliar metal concentrations with CO2 enrichment, and some essential plant metals were greater under elevated CO2 (for example, 28% increase in Mn across species and sites). Our results suggest that elevated CO2 impacts on trace metal biogeochemistry can be understood by accounting for both metal function (or lack thereof) in plants and the soil characteristics of the ecosystem.
Key wordsbiogeochemical cycles elevated CO2 free-air CO2 enrichment global change micronutrients soil organic matter trace metals
We thank R. Norby, R. Oren, B. Hungate, and the staff at the FACE and SERC sites for field support, and K. Butterbach-Bahl and two anonymous reviewers for comments on this manuscript. This study was supported by grants from the U. S. Department of Energy, Office of Science (BER), and graduate fellowships from the National Science Foundation (S.M.N.) and Department of Energy (S.M.N.).
- Ellsworth DS, Reich PB, Naumburg ES, Koch GW, Kubiske ME, Smith SD. 2004. Photosynthesis, carboxylation and leaf nitrogen responses of 16 species to elevated pCO(2) across four free-air CO2 enrichment experiments in forest, grassland and desert. Global Change Biology 10: 2121-2138.CrossRefGoogle Scholar
- Farquhar G, von Caemmerer S. (1982). Modelling of photosynthetic response to environmental conditions. In: Lange O, Nobel P, Osmond C, Ziegler H, (ed). Encyclopedia of plant physiology vol.12B: Physiological plant ecology II. New York: Springer-Verlag. p549-587.Google Scholar
- Finzi AC, Allen AS, DeLucia EH, Ellsworth DS, Schlesinger WH. 2001. Forest litter production, chemistry, and decomposition following two years of free-air CO2 enrichment. Ecology 82: 470-484.Google Scholar
- IPCC. 2007. Climate change 2007: The physical science basis. Solomon S, Qin D, Manning Z, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL, editors. Contribution of working group I to the fourth assessment report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press. p996.Google Scholar
- Marschner H. 1995. Mineral nutrition of higher plants, 2nd edn. San Diego: Academic Press. 887p.Google Scholar
- Quinn G, Keough M. 2002. Experimental design and data analysis for biologists. New York: Cambridge University Press. 537p.Google Scholar
- Scheiner SM. (2001). MANOVA: Multiple response variables and multispecies interactions. In: Scheiner SM, Gurevitch J, (ed). Design and analysis of ecological experiments. New York: Oxford University Press. p99-115.Google Scholar
- Schmalzer PA, Hinkle CR. 1992. Recovery of oak-saw palmetto scrub after fire. Castanea 57: 158-173.Google Scholar
- Sterner R, Elser J. (2002). Ecological stoichiometry: the biology of elements from molecules to the biosphere, Princeton. Princeton University Press. p439.Google Scholar
- U.S. Environmental Protection Agency (1991) Method 200.3. Sample preparation procedure for spectrochemical determination of total recoverable elements in biological tissues. In: Methods for the determination of metals in environmental samplesGoogle Scholar
- U.S. Environmental Protection Agency (1996) Method 3050B. Acid digestion of sediments, sludges and soils. In: Test methods for evaluating solid waste, physical/chemical methodsGoogle Scholar