PARENT SESSION
Contributed Oral Session 3: Herbivory: Plant - Herbivore Interaction
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 513 E, Level 5, Palais des congrès de Montréal
Aboveground insect herbivores suppress root growth in a native grassland.
Stacey, Jocelyn*,1, Coupe, Malcolm1, Cahill, James1, 1 University of Alberta, Edmonton, Alberta, Canada
ABSTRACT- Although the vast majority of plant biomass is belowground in grassland communities, the focus of plant-herbivore interactions has historically been primarily aboveground. Only recently have studies emerged which have focused primarily on the impacts of feeding on aboveground tissues on changes in root growth dynamics. Though several studies have been published regarding the impacts of large vertebrates, the impact of insect herbivores has largely been ignored. Due to their small size, rapid turnover, and limited movement, insects may influence plant production differently than mammalian grazers. This study examined the impact of aboveground insect herbivory on root growth through a year in a native grassland in Central Alberta, Canada. Twelve plots were established 6 of which were control plots and 6 were sprayed with an insecticide. Minirhizotron tubes were installed and insecticide application initiated in 2001, with data presented here collected in 2002. Root images were taken approximately once a month during the growing season, with images covering the majority of the rooting zone. Preliminary analyses indicated that there existed a pre-treatment difference in root length among the controlled and sprayed plots, and thus all analyses accounted for these differences (ANCOVA). Spraying plots increased leaf cover by 25%, suggesting insect herbivory was common during the field season. Spraying also increased root number and root length relative to the control plots, with the magnitude of differences among treatments increasing through the field season. These results are counter to the findings of recent studies on the effects of vertebrate herbivory on grassland belowground production which had found a stimulatory effect of grazing on root production. It is unclear whether the directly counter results are due to different types of herbivory or due to different study systems.
Key words: herbivory, root demography, grassland, insect