Rapid warming is predicted to increase insect herbivory across the tundra biome, yet how this will impact the community and ecosystem dynamics remains poorly understood. More insect herbivory could reduce potential gains in Arctic plant growth, by serving as a top–down control on tundra vegetation. Additionally, many tundra ecosystems experience severe insect outbreaks, where large numbers of insects emerge and consume large amounts of leaves and other plant material, which can have leaf lasting damage to shrubs. To explore how tundra-insect herbivore systems respond to warming, we measured shrub traits and leaf herbivory damage at 16 sites along a landscape gradient in western Greenland. Here we show that shrub leaf insect herbivory damage on two dominant deciduous shrubs, grey willow (Salix glauca) and dwarf birch (Betula nana), was positively correlated with increasing temperatures throughout the first half of the 2017 growing season. We found that the majority of insect herbivory damage occurred in July, which was outside the period of rapid leaf expansion that occurred throughout most of June. Leaf-chewing insects caused the most leaf damage in both shrub species. Additionally, insect herbivores removed a larger proportion of dwarf birch leaf biomass in warmer sites, which is due to a combination of increased herbivory with a coinciding decline in leaf biomass. These results suggest that the effects of rising temperatures on both insect herbivores and plants are important to consider when predicting the trajectory of Arctic tundra shrub expansion.
Reference: Finger-Higgens, R., DeSiervo, M., Ayres, M.P. and Virginia, R.A., 2021. Increasing shrub damage by invertebrate herbivores in the warming and drying tundra of West Greenland. Oecologia, pp.1-11.
https://doi.org/10.1007/s00442-021-04899-7
Text by Rebecca Finger-Higgens, Darmouth College.
Picture: Fieldwork in Kangerlussuaq (photo credit: Rebecca Finger Higgens)