Long‐Term Drainage Reduces CO₂ Uptake and CH₄ Emissions in a Siberian Permafrost Ecosystem

Abstract

Permafrost landscapes in northern high latitudes with their massive organic carbon stocks are an important, poorly known, component of the global carbon cycle. However, in light of future Arctic warming, the sustainability of these carbon pools is uncertain. To a large part, this is due to a limited understanding of the carbon cycle processes because of sparse observations in Arctic permafrost ecosystems. Here we present an eddy covariance data set covering more than 3 years of continuous CO2 and CH4 flux observations within a moist tussock tundra ecosystem near Chersky in north‐eastern Siberia. Through parallel observations of a disturbed (drained) area and a control area nearby, we aim to evaluate the long‐term effects of a persistently lowered water table on the net vertical carbon exchange budgets and the dominating biogeochemical mechanisms. Persistently drier soils trigger systematic shifts in the tundra ecosystem carbon cycle patterns. Both, uptake rates of CO2 and emissions of CH4 decreased. Year‐round measurements emphasize the importance of the non‐growing season—in particular the “zero‐curtain” period in the fall—to the annual budget. Approximately 60% of the CO2 uptake in the growing season is lost during the cold seasons, while CH4 emissions during the non‐growing season account for 30% of the annual budget. Year‐to‐year variability in temperature conditions during the late growing season was identified as the primary control of the interannual variability observed in the CO2 and CH4 fluxes.

Where old meets new: An ecosystem study of methanogenesis in a reflooded agricultural peatland

“…Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory (LLNL). Sediment and plant stem gas samples were purified to isolate CH 4 for δ 13 C and ∆ 14 C isotope analyses on a cryogenic extraction line based on Zimov et al (2017) andPetrenko et al (2008). Samples were introduced to the vacuum line at ambient pressure.…”

Species interactions and distinct microbial communities in high Arctic permafrost affected cryosols are associated with the CH4 and CO2 gas fluxes

“…Indeed, laboratory and field warming experiments predict net positive C losses from Arctic permafrost affected soils (Natali et al ., ; Stackhouse et al ., ; Mauritz et al ., ; Raz‐Yaseef et al ., ). These results mirror large‐scale studies demonstrating that permafrost affected soils are current net sources of C, despite increased atmospheric C uptake due to a longer growing season (Belshe et al ., ; Lara et al ., ; Natali et al ., ; Kittler et al ., ).…”

“…Warming will likely increase the amount of C lost to the atmosphere from permafrost soils; however, the ratio of CH 4 :CO 2 released is currently uncertain and would likely be determined by the geomorphology, hydrology, vegetation and microbiology of these soils (Lara et al, 2015;Natali et al, 2015;Mackelprang et al, 2016). Permafrost thaw would affect soil topography and increase moisture content in areas with high ice content in the permafrost but thaw can also induce drying via drainage and changes in hydrology in parts of the Arctic (Natali et al, 2015;Kittler et al, 2017). Drainage disturbance and drying in Arctic tundra habitats increase CO 2 emissions but decrease CH 4 emissions (Kittler et al, 2017), possibly due to anaerobic habitat loss that favours methanogesis.…”

“…Permafrost thaw would affect soil topography and increase moisture content in areas with high ice content in the permafrost but thaw can also induce drying via drainage and changes in hydrology in parts of the Arctic (Natali et al, 2015;Kittler et al, 2017). Drainage disturbance and drying in Arctic tundra habitats increase CO 2 emissions but decrease CH 4 emissions (Kittler et al, 2017), possibly due to anaerobic habitat loss that favours methanogesis. Therefore, a warmer climate with drier soils may decrease CH 4 emissions and increase CH 4 uptake in parts of the Arctic, likely due to aerated soils promoting methanotrophy (Emmerton et al, 2014;Lara et al, 2015).…”

“…Therefore, a warmer climate with drier soils may decrease CH 4 emissions and increase CH 4 uptake in parts of the Arctic, likely due to aerated soils promoting methanotrophy (Emmerton et al, 2014;Lara et al, 2015). However, this could also result in areas of saturated ground that could promote methanogenesis and act as CH 4 sources (Kittler et al, 2017).…”