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Blue Alder Leaf Beetles vs. Silver Birch Seedlings
Reference
Huttunen, L., Niemela, P., Julkunen-Titto, R., Heiska, S., Tegelberg, R., Rousi, M. and Kellomaki, S. 2008. Does defoliation induce chemical and morphological defenses in the leaves of silver birch seedlings under changing climate? Chemoecology 18: 85-98.

What was done
In a study of first-year silver birch (Betula pendula) seedlings grown in climate-controlled closed-top chambers maintained at ambient and twice-ambient atmospheric CO2 concentrations and at ambient and ambient plus 2C air temperatures, the authors examined the additional effects of three levels of added soil nitrogen (none, moderate and high) plus two levels of manual defoliation (25% and 50%), as well as leaf palatability to adult blue alder leaf beetles (Agelastica alni), while they periodically measured a host of seedling parameters related to plant chemical and morphological defense properties.

What was learned
As might be imagined, the researchers' findings were varied and complex, indicative of complicated interactions that had the potential to cascade through several trophic levels and change the dynamics of forest ecosystems. "In the worst scenario," as they describe what could possibly happen, "the consequences may include widespread damage to trees." However, as they report, their study indicated that the blue alder leaf beetle's "total leaf consumption was higher under the ambient climatic conditions than under elevated temperature, elevated CO2, or the combination of elevated temperature and CO2."

What it means
Since Huttunen et al.'s bottom-line findings were just the opposite of what they call the worst thing they could envision happening to silver birch seedlings in a CO2-enriched and warmer world in terms of insect pest herbivory, we can only conclude that elevated temperature alone, elevated CO2 alone, or the combination of elevated temperature and elevated CO2 together actually produced the best thing that could happen to silver birch seedlings with respect to damage that could be inflicted upon them by the blue alder leaf beetle.

Reviewed 23 July 2008