Invertebrate herbivory in the tundra is prevalent and sensitive to climate change.

Recent studies have shown that biotic interactions influence macroecological patterns and global dynamics, stressing the need to consider them outside local or regional scales. In the context of global changes affecting the dynamics and fate of whole biomes, we still know little about the role of key biotic interactions. In this study, the intensity of invertebrate background herbivory (low intensity but chronic biomass removal) on one common tundra plant (Betula nana-glandulosa complex) is investigated along the tundra biome in relation to latitude and climate.

Tundra in Svalbard through pinhole (pic by Lauri Laanisto)

C. Guillermo Bueno from the University of Tartu was part of the research team led by Isabel C. Barrio and Mikhail V. Kozlov. They collected samples from 56 locations across the tundra biome in the first coordinated effort to measure invertebrate herbivory in tundra, outside the well-studied effects of insect outbreaks. Background herbivory was detected at nearly all tundra sites. The intensity of background herbivory, although low, was mainly associated with higher temperatures and, as such, is likely to increase in a warmer Arctic. This paper represents the first coordinated effort combining two international research networks in the tundra: the Herbivory Network and NeAT (Network for Arthropods of the Tundra).

Citation: Barrio, I. C., Lindén, E., Te Beest, M., Olofsson, J., Rocha, A., Soininen, E. M., … Bueno, C. G, … & Bråthen, K. A. (2017). Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome. Polar Biology, doi:10.1007/s00300-017-2139-7 (link to full text)

Trend of herbivory (damaged leaves) along the temperature gradient in the tundra sites

Location of the sites, with the size of the circles relative to the number of samples taken (see full publication for details)

Abstract:

Chronic, low intensity herbivory by invertebrates, termed background herbivory, has been understudied in tundra, yet its impacts are likely to increase in a warmer Arctic. The magnitude of these changes is however hard to predict as we know little about the drivers of current levels of invertebrate herbivory in tundra. We assessed the intensity of invertebrate herbivory on a common tundra plant, the dwarf birch (Betula glandulosa-nana complex), and investigated its relationship to latitude and climate across the tundra biome. Leaf damage by defoliating, mining and gall-forming invertebrates was measured in samples collected from 192 sites at 56 locations. Our results indicate that invertebrate herbivory is nearly ubiquitous across the tundra biome but occurs at low intensity. On average, invertebrates damaged 11.2% of the leaves and removed 1.4% of total leaf area. The damage was mainly caused by external leaf feeders, and most damaged leaves were only slightly affected (12% leaf area lost). Foliar damage was consistently positively correlated with mid-summer (July) temperature and, to a lesser extent, precipitation in the year of data collection, irrespective of latitude. Our models predict that, on average, foliar losses to invertebrates on dwarf birch are likely to increase by 6–7% over the current levels with a 1 °C increase in summer temperatures. Our results show that invertebrate herbivory on dwarf birch is small in magnitude but given its prevalence and dependence on climatic variables, background invertebrate herbivory should be included in predictions of climate change impacts on tundra ecosystems.