The effects of insect herbivory on temperate forest species under experimental CO2 enrichment

Background/Question/Methods: Global climate change is impacting forest health and increasing the frequency and severity of disturbances. It is difficult to thoroughly project future climate scenarios because of the uncertain effects from feedbacks of terrestrial processes to the atmosphere. Measurements of insect herbivory provide insights into patterns of ecosystem change. Nutrients transferred into the soil via herbivory are comparable to the nutrients transferred via other important nutrient sources. In contrast to common theories, herbivory may increase nutrient fluxes of nitrogen and phosphorus even in unproductive ecosystems. Even though insect herbivory has a high impact on forest biogeochemical cycling there is not enough information to accurately predict ecosystem structure and function with the changing environment in global models. Free air carbon dioxide (CO2) enrichment (FACE) experiments are considered the most reliable approach for quantifying our expectations of forest ecosystem responses to changing atmospheric CO2 concentrations. Roughly a 28% increase to 550 ppm carbon dioxide enrichment was applied in a temperate forest in Birmingham, UK for three growing seasons 2017-2019.

Results/Conclusions: It is predicted that CO2 enrichment lowers the nutritional quality of leaves which may increase insect herbivory in order to meet their nutritional demands. Overall, CO2 enrichment suggests no significant differences in insect herbivory patterns between enriched and ambient conditions but does show a significant tree species effect. Preliminary results show a significant decrease in insect herbivory for Cretaegus monogyna and a significant increase of insect herbivory for Quercus robur. Suggesting that herbivory could make major contributions to nutrient cycling, and influence ecosystem change even in enriched CO2 conditions. Understanding the effects of enriched CO2 on herbivory in forest ecosystems globally could help to develop sustainable forest management practices.