Integrating Stream, River and Lake Components of CO2 Fluxes into Boreal Landscape Perspective

C Teodoru (teodoru.cristian@courrier.uqam.ca); P A del Giorgio (del_giorgio.paul@uqam.ca); [*Y T Prairie*] (prairie.yves@uqam.ca)
GRIL-Département des sciences biologiques, UQÀM, Box 8888, succ. Centre-ville, Montréal, Qc Canada H3C 3P8 (ph.514-987-3000 x.4870#; fax: 514-987-4647)

We developed some simple empirical rules to predict pCO2 in a variety of streams, rivers and lakes of the boreal landscape near Eastmain, Quebec. These rules were then applied to upscale these three aquatic components in two randomly chosen sections of the landscape, each covering about 970 km2, to estimate the individual contribution of each aquatic compartment (river, lake and stream) in terms of area and CO2 fluxes. Annual C emissions from the ensemble of aquatic ecosystems of the two selected areas were calculated as 3257 and 2343 t C yr-1, and the relative contribution of the various systems to this flux was greatly influenced by the presence or absence of large rivers. Lakes represented 67% and 98%, respectively of the surface area of aquatic systems, and contributed 34% and 74% to the net C emissions, respectively. Large rivers represented 31% and 0.8%, respectively, of the aquatic areas and contributed 41% and 3% to total C emissions. Streams on the other hand, despite their small areal coverage (1.1% and 0.7% of the total aquatic surface) accounted for a surprising 25% and 23%, respectively, of the total aquatic C emissions. We further examined how the variability in relative contribution of the various aquatic components is reduced with increasing spatial scale. Expressed on a whole-watershed areal basis, aquatic CO2 emissions were estimated to range between 2 and 3 g m-2 yr-1, or about equivalent to terrestrial NEP in that region.

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