Wintertime CO₂ efflux from Arctic soils: Implications for annual carbon budgets

Abstract

Abstract. Estimates of annual carbon loss from arctic tundra ecosystems are based nearly entirely on measurements taken during the growing season in part because of methodological limitations but also reflecting the assumption that respiration during winter is near zero. Measurements of CO2 flux during winter, however, indicate significant amounts of carbon loss from tundra ecosystems throughout the 240-day nongrowing season. In our study during the 1996 and 1997 nongrowing seasons, winter carbon losses ranged from 2.0 g CO2 m -2 season '1 in moist dwarf shrub communities to 97 g CO2 m '2 season '1 in natural snowdrift communities, with an average wintertime CO2 efflux of 45 g CO2 m -2 for all Low Arctic tundra communities (0.14 Pg CO2 yr 'l worldwide). These measurements indicate that current estimates of annual carbon loss from tundra ecosystems are low. Inclusion of wintertime losses of CO2 into annual carbon budgets increases the annual carbon efflux of arctic tundra ecosystems by 17% and changes some ecosystems from net annual sinks to net sources of CO2 to the atmosphere.

Winter greenhouse gas fluxes (CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O) from a subalpine grassland

“…CO 2 flux measurements reported in this study were generally in the upper range of winter emissions reported in the literature Skinner, 2007;Sommerfeld et al, 1996;Filippa et al, 2009;Liptzin et al, 2009;Rogiers et al, 2008;Brooks et al, 1997;Fahnestock et al, 1999). Whereas our results showed a clear seasonal pattern with (i) gradual decreases at the beginning of the snow-covered period, (ii) a mid-winter minimum, and (iii) increases in CO 2 flux during snowmelt, studies undertaken in the Rocky Mountains showed completely opposite behavior of steadily increasing CO 2 fluxes with progressing winter (Sommerfeld et al, 1996, Monson et al, 2006a.…”

“…There is also only one single study that explicitly measured the spatial variability of soil CO 2 effluxes for different ecosystem types during winter in Arctic Alaska . Case studies showed that soil CO 2 efflux ranged between 0.7 and 770 g CO 2 -C m −2 during the long snow-covered season, which corresponded to 10 to 40 % of the annual effluxes in arctic and subalpine ecosystems (Winston et al, 1997;Clein and Schimel, 1995;Melloh and Crill, 1996;Nykanen et al, 1995;Aurela et al, 2002;Fahnestock et al, 1999;Björkman et al, 2010b).…”

Response of carbon dioxide emissions to sheep grazing and N application in an alpine grassland – Part 1: Effect of sheep grazing

“…R e outside the growing season contributed 21.5 % in short-term grazing exclusion and 6.8 % in longterm grazing exclusion to the annual respiration emissions, which were similar to a sub-alpine grassland at Rigi Seebodenalpin (23.3 %) (Merbold et al, 2012). In addition, the CO 2 flux (2.1-16.8 mg m −2 h −1 ) outside the growing season from the alpine grassland in our study was comparable with previous studies in arctic tundra (2.5-7.5 mg m −2 h −1 ) (Fahnestock et al, 1999;Bubier et al, 2002), in temperate semiarid steppe (3.3-9.6 mg m −2 h −1 ) (Chen et al, 2013), and in sagebrush steppe (7.5-15.0 mg m −2 h −1 ) (Gilmanov et al, 2004). However, soil CO 2 emissions during the growing season (483.4-504.2 mg m −2 h −1 ) were lower than in subalpine grassland (610.0-810.0 mg m −2 h −1 ) (Rich et al, 2013).…”

Two Decades of Experimental Manipulations of Heaths and Forest Understory in the Subarctic

“…Wintertime C losses can account to a significant part of the annual C budget (Fahnestock et al 1999), and the C efflux is likely to increase if the snow depth increases (Welker et al 2000;Larsen et al 2007a). In the mesic heath, cold-season (October-May) respiration accounted for 22 % of the annual respiratory CO 2 release, and rather surprisingly, photosynthetic activity outside the growing season accounted for 19 % of the annual gross CO 2 uptake, partly compensating for the respiratory C losses (Larsen et al 2007b).…”