Global climate change models predict changes in precipitation patterns (larger rainfall events separated by longer dry periods) as well as increased temperatures. Predicting the effects of these forecasted changes on rates of damage from herbivores is not straightforward.  In this study, we compared insect herbivore damage to the common forb, Solidago canadensis (Canada goldenrod), under the rainfall and temperature treatments of the Rainfall Manipulation Plots (RaMPs) at Konza Prairie Biological Station, Manhattan, KS. The experimental shelters that make up the RaMPs project include 6 ambient rainfall treatments and 6 delayed rainfall treatments in which inter-rainfall intervals are increased by 50%. All 12 plots are divided into 4 2x2-m subplots: 2 ambient-temperature controls and 2 warmed by infrared lamps. We censused damage to S. canadensis plants in June and September of 2005 and 2006. We also measured plant size, growth rate, and leaf characteristics including water content, specific leaf mass, and C:N ratio.

Results/Conclusions

Our preliminary analyses indicate weak effects of increased temperature and prolonged dry periods on herbivory, but such differences depended on timing of sampling and year. Rainfall and temperature manipulations affected some leaf traits of relevance to herbivores (leaf water content and C:N ratios), but the strength of effects differed across years. Blister galls formed by a cecidomyiid fly were more frequent on plants in the ambient rainfall and temperature treatment. Our results suggest that interpreting insect responses to climate-related manipulations likely requires more information about the feeding behavior and scale of movement of major herbivores. In addition, insect responses to climate manipulations may depend on how microclimate influences feeding decisions and residence time in patches.