While wildfire is considered the dominant disturbance in boreal forests, fire only recently has been recognized as an important control on peatland carbon cycling. With NSERC funding, we are conducting field studies to examine controls on carbon emissions during peatland fires and with ecosystem succession. With funding from NASA, we are conducting integrated field and remote sensing studies to understand the multiscale controls on fire behaviour in complex boreal landscapes.
We are particularly interested in smouldering combustion, and how this generates unique emissions that can have human health consequences and also influence atmospheric radiative forcing. Beyond the immediate effects of fire, we are conducting research on how fire alters long-term vegetation succession and permafrost stability.
The APEX project is funded by the National Science Foundation, with additional support from the Bonanza Creek Long Term Research Program and the U.S. Geological Survey. The overall goal of this research is to further knowledge about peatland carbon cycling through a series of warming and hydrological experiments.
We initiated a drought and flooding experiment in 2004, and since then we have monitored the effects of drought, flooding, and soil warming on peatland vegetation, greenhouse gas fluxes, and hydrology. Students participating in the APEX project spend their summers in Alaska conducting field work. Our field sites are located about 1 hour outside of Fairbanks, and students also interact with LTER scientists. As one of the longest-running peatland manipulation programs in the world, we are able to test paradigms about how these ecosystems function.
Thaw of ice-rich permafrost
Permafrost soils contain more than half of the global soil carbon pool, far exceeding the amount of carbon in the atmosphere. Release of thawing permafrost carbon is one of the most likely positive feedbacks from terrestrial ecosystems to the atmosphere with warming. While many field and modelling studies examine gradual vertical thaw that occurs with thickening of the seasonal active layer, our lab focuses on subsidence and thermokarst expansion occurring with thaw of ice-rich permafrost. There are earth system or climate models currently considering the role of thermokarst in permafrost-climate feedbacks, but we hope to change this!
The effect of plant traits on ecosystem function
A running theme through many of our research projects is the effect of plant physiology and traits on aspects of ecosystem function. Given that most northern wetlands are covered with a near-continuous ground-layer of mosses, we are trying to understand the controls of various moss groups on soil thermal conditions, substrate quality, and nutrient cycling. We often think about the evolutionary and physiological underpinnings of moss traits that influence ground temperatures and nutrient cycling. We also are interested in changing plant community composition (as a result of changing climate or plant invasion), and the consequences of altered biodiversity for carbon and nitrogen cycling.
Changing climate and northern food
We study how permafrost thaw affects the ability of subsistence harvesters to travel and access traditional foods. We are working with communities to identify how thermokarst is affecting culturally important lands. Many models also show that northern Canada will become more suitable for certain crops under future climate change. This makes the north one of the most important agricultural frontiers. Productivity on northern soils will require drainage, which causes large carbon emissions. We are using a number of approaches to help build capacity in northern communities to better adjust to this shifting agricultural landscape and embrace climate-smart food production and agriculture.
Sustainable water and energy in remote regions
Through collaborations with aquatic biologists, land managers, and remote sensing experts, we are linking changes on land occurring with warming, increasing wildfire and permafrost degradation to changes in streamflow, water quality, and aquatic health. Changes in permafrost stability have important consequences for energy availability for several northern cities that depend on hydropower. In recent years, there has been insufficient flow to generate power in Yellowknife, which is linked to permafrost thaw, and the city was forced to switch to diesel power. Photo credit to Peter Griffiths at NASA.
Fun fact - you can see the APEX water table manipulation plots from space! We have maintained this long-term ecosystem experiment since 2004, and have been tracking changes in vegetation, microbial processes, and carbon fluxes ever since. Hover over the field image below to see the layout of our plots.
To complement the water table manipulation experiment highlighted above, we also have been studying ecosystem responses to wetting caused by the thaw of ice-rich permafrost. We have a lot of infrastructure at the field sites pictured below, including two eddy covariance towers, many networks of chambers, snow and ERT transects, and deep versus shallow nutrient fertilization.