Abstract
Polygonal peatlands are carbon-rich permafrost ecosystems that will likely be significantly affected by climate change. However, studies are often constrained to one measurement per day, which impedes assessments of the temporal variability in carbon fluxes. For this reason, we measured ecosystem respiration (ER) of CO2 in a polygonal peatland underlain by continuous permafrost over an entire growing season to determine the effects of temperature and water table depth on the temporal variability of ER. We used four automated closed chambers to measure ER under varying temperature and soil moisture regimes. Temporal variability was approximately the same for the four plots, on both a diurnal and a seasonal scale. Both diurnal and seasonal variations in ER were strongly controlled by changes in soil surface temperature. Fluctuations of the water table depth associated with important rainfall events was also an important factor affecting ER on the seasonal scale. We found that water table level fluctuations below 20–25 cm did not significantly affect ER and that most soil respiration took place in the top 10 cm, likely in the surface 2 cm. Our results highlight the importance of monitoring future changes in tundra hydrology, which will determine the depth of organic matter available for aerobic decomposition.
Highlights
Over the past 30 years, high latitude regions have experienced an increase in surface temperatures greater than any other part of the world (McBean et al 2005; Turner et al 2007)
Ecosystem respiration in the polygonal peatland was mainly controlled by changes in soil surface temperature
Soil surface temperature was the main factor controlling variations in ecosystem respiration on a seasonal scale, but variations were influenced by the fluctuating depth of the water table in the active layer associated with important rainfall events
Summary
Over the past 30 years, high latitude regions have experienced an increase in surface temperatures greater than any other part of the world (McBean et al 2005; Turner et al 2007). Permafrost degradation caused by climate change is a concern because of the potential release of the carbon that is stored in the northern circumpolar permafrost zone. This zone holds the world’s largest soil organic carbon reservoir with a total estimated content of 1455±125 PgC (1 PgC = 1015 grams of carbon), which represents approximately half of the earth’s belowground organic carbon pool (Tarnocai et al 2009; Schuur et al 2015). Projected changes in climate over the long-term are likely to cause widespread permafrost thaw, leading to the release of greenhouse gases from the decomposition of frozen carbon stocks (Walter et al 2006; Davidson and Janssens 2006; Schuur et al 2008, 2009; Schuur and Abbott 2011)
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