Do elevated atmospheric CO₂ and O₃ affect food quality and performance of folivorous insects on silver birch?

Abstract

The individual and combined effects of elevated CO 2 and O 3 on the foliar chemistry of silver birch (Betula pendula Roth) and on the performance of five potential birch-defoliating insect herbivore species (two geometrid moths, one lymantrid moth and two weevils) were examined. Elevated CO 2 decreased the water concentration in both short-and long-shoot leaves, but the effect of CO 2 on the concentration of nitrogen and individual phenolic compounds was mediated by O 3 treatment, tree genotype and leaf type. Elevated O 3 increased the total carbon concentration only in short-shoot leaves. Bioassays showed that elevated CO 2 increased the food consumption rate of juvenile Epirrita autumnata and Rheumaptera hastata larvae fed with shortand long-shoot leaves in spring and mid-summer, respectively, but had no effect on the growth of larvae. The contribution of leaf quality variables to the observed CO 2 effects indicate that insect compensatory consumption may be related to leaf age. Elevated CO 2 increased the food preference of only two tested species: Phyllobius argentatus (CO 2 alone) and R. hastata (CO 2 combined with O 3 ). The observed stimulus was dependent on tree genotype and the measured leaf quality variables explained only a portion of the stimulus. Elevated O 3 decreased the growth of flush-feeding young E. autumnata larvae, irrespective of CO 2 concentration, apparently via reductions in general food quality. Therefore, the increasing tropospheric O 3 concentration could pose a health risk for juvenile early-season birch folivores in future. In conclusion, the effects of elevated O 3 were found to be detrimental to the performance of early-season insect herbivores in birch whereas elevated CO 2 had only minor effects on insect performance despite changes in food quality related foliar chemistry.

Atmospheric change alters foliar quality of host trees and performance of two outbreak insect species

“…However, efficiency of conversion of digested foliage into biomass was reduced more for forest tent caterpillars than gypsy moths, potentially explaining the more pronounced effect of elevated O 3 on forest tent caterpillars, compared with gypsy moths. Our results agree with a recent study finding that elevated O 3 reduced the performance of multiple early season folivores feeding on silver birch (Peltonen et al 2010). Additionally, our performance results are consistent with findings that forest tent caterpillars fed ozonated foliage preferred birch to aspen, and that aspen foliage from elevated O 3 increases consumption (Agrell et al 2005).…”

“…Nitrogen consistently produced the most positive relationship with growth and the most negative relationship with consumption and frass produced for both herbivores. These results are similar to those of Peltonen et al (2010) who, using PLSR, found that nitrogen had the highest positive and negative relationship with growth and consumption, respectively, for the autumnal moth, Epirrita autumnata. Lignin had the strongest negative relationship with growth for both herbivores.…”

“…This finding is in contrast with recent meta-analyses showing that herbivore growth is often reduced when insects are fed foliage from elevated CO 2 (Zvereva and Kozlov 2006;Stiling and Cornelissen 2007). However, insect performance under elevated CO 2 has been shown to vary depending on both the tree and insect species studied, and findings of unchanged growth or even increased growth of herbivores feeding on foliage from elevated CO 2 environments have been reported multiple times (Lindroth et al 1993;Roth and Lindroth 1995;Kinney et al 1997;Kopper et al 2001;Holton et al 2003;Williams et al 2003;Kopper and Lindroth 2003a;Hättenschwiler and Schafellner 2004;Knepp et al 2007;Peltonen et al 2010;Vigue and Lindroth 2010). Our findings of increased growth by gypsy moths and forest tent caterpillars fed aspen foliage from elevated CO 2 also contrast with previous studies of aspen-herbivore interactions (Lindroth et al 1993;Roth and Lindroth 1995).…”

Responses of leaf beetle larvae to elevated [CO2] and temperature depend on Eucalyptus species

“…Compensatory feeding is often observed at C E in response to decreased foliar [N] (Stiling and Cornelissen 2007;Peltonen et al 2010). Leaf mass consumed by P. atomaria larvae increased at C E , indicating larvae attempted to compensate for the decrease in foliar nutrient content at C E .…”

Ecophysiological Responses of Northern Birch Forests to the Changing Atmospheric CO2 and O3 Concentrations

“…Birch leaves are relatively undesirable as food for insects when the concentrations of CO 2 and O 3 are both high because phenolic compounds increases more under CO 2 + +O 3 enrichment than with CO 2 alone (Peltonen et al, 2010;Karonen et al, 2006;Agrell et al, 2005;Kopper et al, 2001;Lindroth et al, 2001). Besides aboveground C dynamics, atmospheric changes can alter belowground C dynamics through changes in foliar chemistry.…”