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Long-Term Effects of Atmospheric CO2 Enrichment on Plant-Insect Interactions

Stiling, P., Moon, D., Rossi, A., Forkner, R., Hungate, B.A., Day, F.P., Schroeder, R.E. and Drake, B. 2013. Direct and legacy effects of long-term elevated CO2 on fine root growth and plant-insect interactions. New Phytologist: 10.1111/nph.12295.
In the words of Stiling et al. (2013), "increasing atmospheric CO2 concentrations alter leaf physiology, with effects that cascade to communities and ecosystems." However, they say that "responses over cycles of disturbance and recovery are not well known, because most experiments span limited ecological time." So they thus set out to conduct a study that they hoped would overcome this common limitation.

Specifically, Stiling et al. studied the effects of elevated CO2 on root growth, herbivory and arthropod biodiversity in a woodland from 1996 to 2006, using mini-rhizotrons to study root growth, leaf censuses to study herbivory, and pitfall traps to determine the effects of elevated CO2 on arthropod biodiversity. This they did at NASA's Kennedy Space Center in Florida (USA) in a scrub-oak/palmetto ecosystem that was dominated by three species of oak - myrtle oak (Quercus myrtifolia), sand-live oak (Q. geminata) and Chapman oak (Q. chapmanii) - which together accounted for 85-90% of the ecosystem's plant biomass, while 27 other species (including the nitrogen-fixing legume Galactia elliottii) comprised the rest of the biomass. And it was within this ecosystem that they established 16 open-top chambers, each 2.5 m in height with octagonal sides of 1.4-m length which were maintained at either ambient CO2 or enriched CO2 (ambient + 350 ppm CO2).

Over the course of their study, the eight researchers determined that elevated CO2 reduced the number of leaves damaged by leaf miners, leaf tiers, leaf chewers, eyespot galls and other leaf galls for all three oak species as well as the one legume they studied in both of the years (2001 and 2002) that they focused on this subject. And they report that these results were "similar to those of other studies, most of which have also found reductions in insect herbivory under elevated CO2," citing Lincoln et al. (1993), Watt et al. (1995), Bezemer and Jones (1998), Hunter (2001), Whittaker (2001), Stiling and Cornelissen (2007), Lindroth (2010) and Robinson et al. (2012)." And after the end of their decade-long experiment, Stilling et al. determined that fine-root biomass in the CO2-enriched plots was 18% greater, 14% greater and 23% greater than it was in the ambient-treatment plots in March 2007, August 2007 and May 2008, respectively.

In concluding the report of their findings, Stiling et al. write that "the legacy of 10 years of elevated CO2 on plant-herbivore interactions in this system appear to be minimal, indicating that the effects of elevated CO2 may not accumulate over cycles of disturbance and recovery."

Additional References
Bezemer, T.M. and Jones, T.H. 1998. Plant-insect herbivore interactions in elevated atmospheric CO2, quantitative analyses and guild effects. Oikos 82: 212-222.

Hunter, M.D. 2001. Effects of elevated atmospheric carbon dioxide on insect-plant interactions. Agricultural and Forest Entomology 3: 153-159.

Lincoln, P.E., Fajer, E.D. and Johnson, R.H. 1993. Plant-insect herbivore interactions in elevated CO2. Trends in Ecology and Evolution 8: 64-68.

Lindroth, R. 2010. Impacts of elevated atmospheric CO2 and O3 in forests: phytochemistry, trophic interactions and ecosystem dynamics. Journal of Chemical Ecology 36: 2-21.

Robinson, E.A., Ryan, G.D. and Newman, J.A. 2012. A meta-analytical review of the effects of elevated CO2 on plant-arthropod interactions highlights the importance of interacting environmental and biological variables. New Phytologist 194: 321-336.

Stiling, P. and Cornelissen, T. 2007. How does elevated carbon dioxide (CO2) affect plant-herbivore interactions? A field experiment and meta-analysis of CO2-mediated changes on plant chemistry and herbivore performance. Global Change Biology 13: 1823-1842.

Watt, A.D., Whittaker, J.B., Docherty, M., Brooks, G. , Lindsay, E. and Salt, D.T. 1995. The impact of elevated atmospheric CO2 on insect herbivores. In: Harrington, R. and Stork, N.E. (Eds.). Insects in a Changing Environment: Symposium of the Royal Entomological Society. Academic Press, London, United Kingdom, pp. 507-518.

Whittaker, J.B. 2001. Insects and plants in a changing atmosphere. Journal of Ecology 89: 507-518.

Archived 3 December 2013