Upscaling of CO2 Fluxes from Heterogeneous Tundra Plant Communities in Arctic Alaska

TitleUpscaling of CO2 Fluxes from Heterogeneous Tundra Plant Communities in Arctic Alaska
Publication TypeJournal Article
Year of Publication2012
AuthorsKade A, Bret-Harte SM, Euskirchen ES, Edgar C, Fulweber RA
JournalJournal of Geophysical Research
Date Published11/2012
Keywordsarctic tundra vegetation, chamber measurements, eddy covariance, Net ecosystem carbon exchange, plant functional types

We characterized the tundra vegetation at three eddy covariance towers located along a

toposequence in northern Alaska and studied seasonal variations in plot-level CO2 fluxes

among the dominant vegetation types with chambers during the summer and with the

gradient-diffusion technique during the winter. We performed footprint analyses to

determine the source areas contributing to the tower fluxes and scaled plot-level to

eddy-covariance CO2 data based on the proportion of vegetation types occurring within the

footprints. At peak growing season, both gross ecosystem exchange and ecosystem

respiration were greater in moist acidic tussock tundra and wet sedge tundra than in dry

heath tundra. This resulted in relatively similar values of net ecosystem exchange as

measured by chambers in July in tussock tundra across all topographic positions and wet

sedge tundra (2.4 to 4.2 mmol CO2/m2/s) but low values in dry heath tundra

(0.4 mmol CO2/m2/s). Winter respiration was highest for tussock tundra in December,

but there were no significant differences among vegetation types in February and April.

Net and gross ecosystem exchange scaled up from summer chamber measurements

compared well to tower data (r2 = 0.84 and r2 = 0.78, respectively), especially on level

terrain, whereas plot-level CO2-flux measurements in the winter did not agree well with

tower data. This is one of few studies to compare plot-level and tower fluxes during both

summer and winter and to demonstrate successful upscaling of carbon exchange in Arctic

tundra systems under certain conditions.