Carbon and energy exchange processes in Canadian Arctic tundra ecosystems

Subarctic and arctic ecosystems store vast amounts of carbon (C) within soils that are frozen and/or saturated for the majority of the year, however, the response of C cycling in these environments to current and future climate change is uncertain. The net exchange of greenhouse gases such as carbon dioxide (CO2) and methane (CH4) between these ecosystems and the atmosphere dictates whether positive feedbacks associated with surface warming will accelerate climate change.

As part of the Canadian Tundra Carbon Exchange Study established in 2004 with Peter Lafleur at Trent University, our research investigates the biotic and abiotic controls on energy, water, and carbon fluxes between a variety of arctic surfaces and the atmosphere.  This research is located at the Daring Lake Tundra Ecosystem Research Station operated by the Government of the Northwest Territories about 300 km NE of Yellowknife, NT.  The fly-in camp on Daring Lake is about 70 km north of the tree line and hosts a variety of tundra types including wet sedge meadows, tussock tundra, upland low shrub to tall shrub tundra, and wind-swept esker and exposed rocky outcrops.  We currently have four eddy covariance towers running at this site and it is now the longest running collection of flux towers operating in the Canadian Arctic. Tundra sites include CA-DL1 (mixed tundra including tussock-sedge, dwarf-shrub, moss tundra and erect dwarf-shrub tundra), CA-DL2 ( Arctic sedge fen), erect dwarf-shrub tundra and low shrub tundra.

We are also collaborating with researchers from Queen’s University at Cape Bounty on Melville Island (CBAWO).  Our one flux tower there gives us a glimpse on CO2 exchange processes during the short High Arctic summer.

Research Highlights:

AGU EOS magazine (vol. 92 (26), pg. 224) “Earlier Arctic snowmelt does not increase carbon sequestration”
Nature Climate Change (vol. 1, pg. 190) “Research Highlights”

Selected Publications:

Lafleur PM, Humphreys ER. 2018.  Tundra shrub effects on growing season energy and carbon dioxide exchange.  Environmental Research Letters, 13, 055001, doi.org/10.1088/1748-9326/aab863

Ge L, Lafleur PM, Humphreys ER. 2017. Respiration from soil and ground cover vegetation under tundra shrubs. Arctic, Antarctic, and Alpine Research, 49(4):537-550.

Martin AF, Lantz TC, Humphreys ER. 2018. Ice wedge degradation and CO2 and CH4 emissions in the Tuktoyaktuk Coastlands, NT. Arctic Science, 4(1): 130-145,  doi.org/10.1139/as-2016-0011.

Emmerton CA, St Louis VL, Humphreys ER, Gamon JA, Barker JD, Pastorello GZ, 2016. Net ecosystem exchange of CO2 with rapidly changing high Arctic landscapes. Global Change Biology, 22, 1185-1200.

Crawford, A.J. D.R. Mueller, E.R. Humphreys, T. Carrieres, and H. Tran.  2015. Surface ablation model evaluation on a drifting ice island in the Canadian Arctic. Cold Reg. Sci. Technol. 110:170-182, doi: 10.1016/j.coldregions.2014.11.011

Grant, R.F., E.R. Humphreys, P.M. Lafleur, 2015.  Ecosystem CO2 and CH4 exchange in a mixed tundra and a fen within a hydrologically diverse Arctic landscape: 1. Modeling versus measurements, Journal of Geophysical Research-Biogeosciences, 120: 1366-1387.

Campeau, A.B., P.M. Lafleur, and E.R. Humphreys, 2014.  Landscape-scale variability in soil organic carbon storage in the central Canadian Arctic, Canadian Journal of Soil Science.  94(4): 477-488, 10.4141/cjss-2014-018

Emmerton, C.A., St. Louis, V.L., Lehnerr, I., Humphreys, E.R., Rydz, E., Kosolofski, H.R. 2014.  The net exchange of methane with high Arctic landscapes during the summer growing season.  Biogeosciences, 11: 3095–3106.

Mbufong, H.N., Lund, M., Aurela, M., Christensen, T.R., Eugster, W., Friborg, T., Hansen, B.U., Humphreys, E.R., Jackowicz-Korczynski, M., Kutzbach, L. et al.  2014.  Assessing the spatial variability in peak season CO2 exchange characteristics across the Arctic tundra using a light response curve parameterization, Biogeosciences, 11: 4897-4912.

Luus, K.A., Kelly, R.E.J., Lin, J.C., Humphreys, E.R., Lafleur, P.M., Oechel, W.C. 2013.  Modeling the influence of snow cover on low Arctic net ecosystem exchange, Environ. Res. Lett. 8, doi:10.1088/1748-9326/8/3/035045

Lafleur, P.M., Humphreys, E.R., Myklebust, M.C., St. Louis, V.L., Papakyriakou, T., Poissant, L., Barker, J.D., Pilote, M. and Swystun, K.A. 2012. Variation in peak growing season net ecosystem production across the Canadian Arctic.  Environmental Science and Technology, doi.org/10.1021/es300500m.

Humphreys, E. R. and Lafleur, P.M. 2011. Does earlier snowmelt lead to greater CO2 sequestration in two low Arctic tundra ecosystems? Geophysical Research Letters, 38, L09703, doi:10.1029/2011GL047339.

Loranty, M. M., Goetz, S.J., Rastetter, E.B., Rocha, A.V., Shaver, G.R., Humphreys, E.R., and Lafleur, P.M. 2011.  Scaling an instantaneous model of tundra NEE to the Arctic landscape.  Ecosystems, 14: 76-93.

Wilson, K. S. and Humphreys, E.R. 2010.  Carbon dioxide and methane fluxes from arctic mudboils.  Canadian Journal of Soil Science, 90: 441-449

Lafleur, P.M. and Humphreys, E.R. 2007.  Spring warming and carbon dioxide exchange over low Arctic tundra in central Canada.  Global Change Biology, 14: 740-756.