Altered performance of forest pests under atmospheres enriched by CO2 and O3

A Corrigendum to this article was published on 09 January 2003


Human activity causes increasing background concentrations of the greenhouse gases CO2 and O31. Increased levels of CO2 can be found in all terrestrial ecosystems2. Damaging O3 concentrations currently occur over 29% of the world's temperate and subpolar forests but are predicted to affect fully 60% by 2100 (ref. 3). Although individual effects of CO2 and O3 on vegetation have been widely investigated, very little is known about their interaction, and long-term studies on mature trees and higher trophic levels are extremely rare4. Here we present evidence from the most widely distributed North American tree species5, Populus tremuloides, showing that CO2 and O3, singly and in combination, affected productivity, physical and chemical leaf defences and, because of changes in plant quality, insect and disease populations. Our data show that feedbacks to plant growth from changes induced by CO2 and O3 in plant quality and pest performance are likely. Assessments of global change effects on forest ecosystems must therefore consider the interacting effects of CO2 and O3 on plant performance, as well as the implications of increased pest activity.

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Figure 1: The effects of elevated CO2 and O3 on the growth of trembling aspen.
Figure 2: The effects of CO2 and O3 on physical and chemical leaf defences in trembling aspen.
Figure 3: Effects of CO2 and O3 on one pathogen and two important herbivorous insects found on aspen a, Melampsora medusae infection; we note that rust increased on leaves exposed to O3 relative to both the control and those exposed to CO2 alone.
Figure 4: Long-term effects of enhanced CO2 and O3 atmospheres on the abundance of aphids (filled circles) and natural enemies (open squares) feeding on aspen.


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The FACTSII: Aspen FACE project is supported by the US Department of Energy-Office of Biological and Environmental Research (DOE-BER) through its Program for Ecosystem Research. The research described herein is supported by companion grants from the US Forest Service Northern Global Change Program, Michigan Technological University, the USDA National Research Initiatives Program, the Canadian Federal Panel on Energy Research and Development (PERD), Natural Resources Canada-Canadian Forest Service, the National Science Foundation, the Natural Environmental Research Council of the United Kingdom, the British Ecological Society and the Praxair Foundation. The Aspen FACE project is an experiment within the International Biosphere Geosphere Programme and the only open-air site in the world that combines the effects of CO2 and O3. It is a multi-agency, interdisciplinary project with 50 scientists from seven countries.

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Correspondence to Kevin E. Percy.

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Percy, K., Awmack, C., Lindroth, R. et al. Altered performance of forest pests under atmospheres enriched by CO2 and O3. Nature 420, 403–407 (2002).

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