Effects of Global Atmospheric Change on Forest Insects

Research Issue

Atmospheric changes, primarily rapidly increasing levels of greenhouse gases such as CO₂ (ca. 2 ppm/yr), ozone, and others are expected to substantially change plant-insect interactions due to their indirect effects on plant defensive and nutritional chemistry that strongly influence both phytophagous and saprophagous insect physiology, behavior, and population dynamics.  Moreover, rising temperatures and changing precipitation and storm patterns are accompanying collateral effects of atmospheric change that also have significant effects on plants and the population processes of insects.

Our Research

We have studied seasonal and annual changes in forest insect populations at the Aspen FACE Experiment site in northern Wisconsin where trees were grown under both elevated CO₂ (+200 ppm above ambient) and ozone (+50% above ambient). Insect parasitoid and diversity abundance studies under these conditions were done to detect patterns of host and parasitoid interaction.  Studies of elevated CO₂ leaf diets from Aspen FACE on respiration rates of laboratory-reared Gypsy moth were done to determine whether effects on first generation metabolism could be discerned.

Expected Outcomes

Paleoecological studies from 50-60 MYA suggest that greenhouse gases suddenly and substantially increased for about 100 thousands years, accompanied by global warming, which triggered increases in herbivory in ancient plant communities.  This may be a foreboding prediction for the 21^st century. Our studies will increase our knowledge about insect parasitoid and diversity abundance under these conditions and a better understanding of host plant-insect-parasitoid interactions.

Research Results

Our data from Aspen FACE studies show that each phytophagous and parasitic forest insect species responds individually to the CO₂ and O₃ effects on plants due to their unique tri-trophic niches, i.e. the confluence of their special plant tissues eaten, interactions with other herbivores, and predators and parasites, all of which are themselves affected by changing levels of greenhouse gases.

Veteli, T.O., Mattson, W.J., Niemelä, P., Julkunen-Tiitto, R., Kellomäki, S., Kuokkanen, K., and Lavola, A.  2007.  Do elevated temperature and CO₂ generally have counteracting effects on phenolic phytochemistry of boreal trees?  J. Chem. Ecol.  33: 287-296.

Mattson, W.J., Julkunen-Tiitto, R., and Herms, D.A. 2005. CO₂ enrichment and carbon partitioning to phenolics: do plant responses accord better with the protein competition or the growth-differentiation balance models?  Oikos 111: 337-347.

Mattson, W.J., Kuokkanen, K., Niemelä , P., Julkunen-Tiitto, R., Kellomäki, S. and Tahvanainen, J.  2004.  Elevated CO₂ alters birch resistance to Lagomorpha herbivores.  Global Change Biology 10: 1402-141.

Research Participants

Principal Investigator

• William J. Mattson, US Forest Service Northern Reserach Station- Research Entomologist Emeritus

Research Partners

• Dan Herms, the Ohio State University, Department of Entomology, Wooster, OH
• Terry Trier, Grand Valley State University, Department of Biology, Allendale, MI 
• Pekka Niemela, Turku University, Biology Department, Turku, Finland
• Riita Julkinen-Tiitto, Joensu University, Biology Department, Joensuu, Finland