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Regional contribution of CO 2 and CH 4 fluxes from the fluvial network in a lowland boreal landscape of Québec
Author(s) -
Campeau Audrey,
Lapierre JeanFrançois,
Vachon Dominic,
Giorgio Paul A.
Publication year - 2014
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/2013gb004685
Subject(s) - fluvial , streams , boreal , greenhouse gas , environmental science , hydrology (agriculture) , atmospheric sciences , physical geography , geology , oceanography , geography , geomorphology , computer network , computer science , paleontology , geotechnical engineering , structural basin
Boreal rivers and streams are known as hot spots of CO 2 emissions, yet their contribution to CH 4 emissions has traditionally been assumed to be negligible, due to the spatially fragmented data and lack of regional studies addressing both gases simultaneously. Here we explore the regional patterns in river CO 2 and CH 4 concentrations ( p CO 2 and p CH 4 ), gas exchange coefficient ( k ), and the resulting emissions in a lowland boreal region of Northern Québec. Rivers and streams were systematically supersaturated in both gases, with both p CO 2 and p CH 4 declining along the river continuum. The k was on average low and increased with stream order, consistent with the hydrology of this flat landscape. The smallest streams (order 1), which represent < 20% of the total river surface, contributed over 35% of the total fluvial greenhouse gas (GHG) emissions. The end of winter and the spring thaw periods, which are rarely included in annual emission budgets, contributed on average 21% of the annual GHG emissions. As a whole, the fluvial network acted as significant source of both CO 2 and CH 4 , releasing on average 1.5 tons of C (CO 2 eq) yr −1 km −2 of landscape, of which CH 4 emissions contributed approximately 34%. We estimate that fluvial CH 4 emissions represent 41% of the regional aquatic (lakes, reservoirs, and rivers) CH 4 emissions, despite the relatively small riverine surface (4.3% of the total aquatic surface). We conclude that these fluvial networks in boreal lowlands play a disproportionately large role as hot spots for CO 2 and more unexpectedly for CH 4 emissions.