Tundra Ecology

My primary research interests involve understanding the ecological and evolutionary consequences of climate change in the tundra, particularly in the Arctic. Why the Arctic? This area has experienced the most rapid warming of anywhere in the world, and this trend is predicted to continue. The Arctic is home to an abundance of wildlife (see the photo gallery for proof!) and the permafrost contains an enormous amount of stored soil carbon. Thus, understanding how climate change will affect Arctic ecosystems is important not only for the Arctic itself, but also for the rest of the planet.

Patterns in plant functional traits

Plant functional traits (e.g., maximum canopy height, specific leaf area, wood density) are often directly related to ecosystem functions (for example, plant height can be related to carbon storage potential, SLA is related to maximum photosynthetic rate).

Salix arctica (Arctic willow) leaves

Thus, understanding how warming will lead to changes in PFT’s will have direct implications for expected changes in ecosystem function. We are using a long-term circumpolar vegetation composition dataset to assess patterns of trait variation over space and community trait change over time to determine which traits (and their associated functions) have the greatest potential to respond rapidly to environmental change.

More on this: Bjorkman, AD, IH Myers-Smith, SC Elmendorf, S Normand, N Rüger, et al. 2018. Plant functional trait change across a warming tundra biome. Nature 562: 57–62. (link)

As part of this effort we established the Tundra Trait Team, which now consists of more than 100 members and a database of nearly 92,000 plant trait observations. The database is publicly available (data paper in Global Ecology and Biogeography). If you are interested in joining the team or finding out more about the TTT database, please get in touch!

Phenological responses to warming

The timing of flowering and other life events is widely expected to advance as temperatures warm. This pattern has frequently been demonstrated in temperate ecosystems as well as at some Arctic sites.  We investigated the phenological responses of Arctic plants to 21 years of both experimental and natural warming at Alexandra Fiord on Ellesmere Island.  These experiments were set up in 1992 as part of the ITEX (International Tundra EXperiment) program, and the timing of flowering and seed maturation has been recorded for several species in nearly every year since then.

ITEX plots at Alexandra Fiord
ITEX plots (passive warming chambers + control plots) at Alexandra Fiord

Interestingly, while experimental warming led to the expected advance in flowering and seed maturation, flowering in the control plots did not advance over time, despite nearly 1.5 °C of warming over the 21 years of the study. This unexpected result was due, in part, to a concurrent delay in snowmelt, likely as a result of increasing winter snowfall. The study was published in Global Change Biology and can be accessed here.

Adaptation to warming over space and time

As the climate warms, species can respond in three (not mutually exclusive) ways: individuals might respond through phenotypic plasticity, species/populations could track their optimal climate northward, and populations could adapt to warming through evolution. If the rate of climate change is too great and species are unable to respond quickly enough, extirpation or extinction could occur. Much of recent scientific literature has dealt with the potential for species to migrate northward, but evolutionary adaptation may also be an important (if less visible) response.

Open-top chamber
Open-top chamber at Alexandra Fiord

The long-term warming experiments at Alexandra Fiord provide an ideal opportunity to assess the potential for short-term adaptation to warmer temperatures. We conducted a series of reciprocal transplant experiments with Oxyria digyna (Mountain sorrel) and Papaver radicatum (Arctic poppy), to determine whether populations have responded to long-term experimental warming in two different habitat types.

We also conducted common garden experiments at Alexandra Fiord to determine whether populations of Arctic plants from more southerly latitudes will be able to survive, and thrive, at northern latitudes under warmer conditions (in the experimentally warmed plots). More about that work here.