Recent change of Arctic tundra ecosystems from a net carbon dioxide sink to a source

Wildfires in the Arctic tundra have become increasingly frequent in recent years and have important implications for tundra ecosystems and for the global carbon cycle. Lake sediment–based records are the primary means of understanding the climatic influences on tundra fires. Sedimentary charcoal has been used to infer climate-driven changes in tundra fire frequency but thus far cannot differentiate characteristics of the vegetation burnt during fire events. In forested ecosystems, charcoal morphologies have been used to distinguish changes in fuel type consumed by wildfires of the past; however, no such approach has been developed for tundra ecosystems. We show experimentally that charcoal morphologies can be used to differentiate graminoid (mean = 6.77; standard deviation (SD) = 0.23) and shrub (mean = 2.42; SD = 1.86) biomass burnt in tundra fire records. This study is a first step needed to construct more nuanced tundra wildfire histories and to understand how wildfire will impact the region as vegetation and fire change in the future.

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Arctic tundra: A source or sink for atmospheric carbon dioxide in a changing environment?

Oecologia ◽

10.1007/bf00377129 ◽

1982 ◽

Vol 53 (1) ◽

pp. 7-11 ◽

Cited By ~ 220

Author(s):

W. D. Billings ◽

J. O. Luken ◽

D. A. Mortensen ◽

K. M. Peterson

Keyword(s):

Carbon Dioxide ◽

Atmospheric Carbon Dioxide ◽

Arctic Tundra ◽

Changing Environment ◽

Atmospheric Carbon

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Environmental controls on ecosystem-scale cold-season methane and carbon dioxide fluxes in an Arctic tundra ecosystem

Biogeosciences ◽

10.5194/bg-17-4025-2020 ◽

2020 ◽

Vol 17 (15) ◽

pp. 4025-4042

Author(s):

Dean Howard ◽

Yannick Agnan ◽

Detlev Helmig ◽

Yu Yang ◽

Daniel Obrist

Keyword(s):

Carbon Dioxide ◽

Methane Emission ◽

Arctic Tundra ◽

Cold Season ◽

The Arctic ◽

Future Climate Change ◽

Climate Change Scenarios ◽

Carbon Dioxide Fluxes ◽

Soil Temperatures ◽

Annual Total

Abstract. Understanding the processes that influence and control carbon cycling in Arctic tundra ecosystems is essential for making accurate predictions about what role these ecosystems will play in potential future climate change scenarios. Particularly, air–surface fluxes of methane and carbon dioxide are of interest as recent observations suggest that the vast stores of soil carbon found in the Arctic tundra are becoming more available to release to the atmosphere in the form of these greenhouse gases. Further, harsh wintertime conditions and complex logistics have limited the number of year-round and cold-season studies and hence too our understanding of carbon cycle processes during these periods. We present here a two-year micrometeorological data set of methane and carbon dioxide fluxes, along with supporting soil pore gas profiles, that provide near-continuous data throughout the active summer and cold winter seasons. Net emission of methane and carbon dioxide in one of the study years totalled 3.7 and 89 g C m−2 a−1 respectively, with cold-season methane emission representing 54 % of the annual total. In the other year, net emission totals of methane and carbon dioxide were 4.9 and 485 g C m−2 a−1 respectively, with cold-season methane emission here representing 82 % of the annual total – a larger proportion than has been previously reported in the Arctic tundra. Regression tree analysis suggests that, due to relatively warmer air temperatures and deeper snow depths, deeper soil horizons – where most microbial methanogenic activity takes place – remained warm enough to maintain efficient methane production whilst surface soil temperatures were simultaneously cold enough to limit microbial methanotrophic activity. These results provide valuable insight into how a changing Arctic climate may impact methane emission, and highlight a need to focus on soil temperatures throughout the entire active soil profile, rather than rely on air temperature as a proxy for modelling temperature–methane flux dynamics.

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The role of soil characteristics on measured and modelled carbon dioxide and energy fluxes for Arctic dwarf shrub tundra sites

10.5194/egusphere-egu2020-11913 ◽

2020 ◽

Author(s):

Gesa Meyer ◽

Elyn Humphreys ◽

Joe Melton ◽

Peter Lafleur ◽

Philip Marsh ◽

...

Keyword(s):

Carbon Dioxide ◽

Growing Season ◽

Cold Season ◽

Soil Characteristics ◽

Heat Fluxes ◽

Dwarf Shrub ◽

The Arctic ◽

Sensible Heat ◽

Shrub Tundra ◽

Tundra Ecosystems

Four years of growing season eddy covariance measurements of net carbon dioxide (CO2) and energy fluxes were used to examine the similarities/differences in surface-atmosphere interactions at two dwarf shrub tundra sites within Canada&#8217;s Southern Arctic ecozone, separated by approximately 1000 km. Both sites, Trail Valley Creek (TVC) and Daring Lake (DL1), are characterised by similar climate (with some differences in radiation due to latitudinal differences), vegetation composition and structure, and are underlain by continuous permafrost, but differ in their soil characteristics. Total atmospheric heating (the sum of latent and sensible heat fluxes) was similar at the two sites. However, at DL1, where the surface organic layer was thinner and mineral soil coarser in texture, latent heat fluxes were greater, sensible heat fluxes were lower, soils were warmer and the active layer thicker. At TVC, cooler soils likely kept ecosystem respiration relatively low despite similar total growing season productivity. As a result, the 4-year mean net growing season ecosystem CO2 uptake (May 1 - September 30) was almost twice as large at TVC (64 &#177; 19 g C m-2) compared to DL1 (33 &#177; 11 g C m-2). These results highlight that soil and thaw characteristics are important to understand variability in surface-atmosphere interactions among tundra ecosystems.As recent studies have shown, winter fluxes play an important role in the annual CO2 balance of Arctic tundra ecosystems. However, flux measurements were not available at TVC and DL1 during the cold season. Thus, the process-based ecosystem model CLASSIC (the Canadian Land Surface Scheme including biogeochemical Cycles, formerly CLASS-CTEM) was used to simulate year-round fluxes. In order to represent the Arctic shrub tundra better, shrub and sedge plant functional types were included in CLASSIC and results were evaluated using measurements at DL1. Preliminary results indicate that cold season CO2 losses are substantial and may exceed the growing season CO2 uptake at DL1 during 2010-2017. The joint use of observations and models is valuable in order to better constrain the Arctic CO2 balance. &#160;

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Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

Remote Sensing of Environment ◽

10.1016/j.rse.2003.10.018 ◽

2004 ◽

Vol 89 (3) ◽

pp. 281-308 ◽

Cited By ~ 401

Author(s):

Douglas A Stow ◽

Allen Hope ◽

David McGuire ◽

David Verbyla ◽

John Gamon ◽

...

Keyword(s):

Remote Sensing ◽

Land Cover ◽

Land Cover Change ◽

Arctic Tundra ◽

Tundra Ecosystems

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Spatial and temporal variations in hectare-scale net CO2 flux, respiration and gross primary production of Arctic tundra ecosystems

Functional Ecology ◽

10.1046/j.1365-2435.2000.00419.x ◽

2000 ◽

Vol 14 (2) ◽

pp. 203-214 ◽

Cited By ~ 34

Author(s):

G. L. Vourlitis ◽

Y. Harazono ◽

W. C. Oechel ◽

M. Yoshimoto ◽

M. Mano

Keyword(s):

Primary Production ◽

Gross Primary Production ◽

Co2 Flux ◽

Arctic Tundra ◽

Temporal Variations ◽

Spatial And Temporal Variations ◽

Tundra Ecosystems

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Estimating CO2 exchange at two sites in Arctic tundra ecosystems during the growing season using a spectral vegetation index

International Journal of Remote Sensing ◽

10.1080/014311699213136 ◽

1999 ◽

Vol 20 (4) ◽

pp. 683-698 ◽

Cited By ~ 38

Author(s):

C. E. McMichael

Keyword(s):

Vegetation Index ◽

Growing Season ◽

Arctic Tundra ◽

Co2 Exchange ◽

Tundra Ecosystems

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Effects of Low Temperature and Freeze-Thaw Cycles on Hydrocarbon Biodegradation in Arctic Tundra Soil

Applied and Environmental Microbiology ◽

10.1128/aem.67.11.5107-5112.2001 ◽

2001 ◽

Vol 67 (11) ◽

pp. 5107-5112 ◽

Cited By ~ 97

Author(s):

Mikael Eriksson ◽

Jong-Ok Ka ◽

William W. Mohn

Keyword(s):

Carbon Dioxide ◽

Arctic Tundra ◽

Carbon Dioxide Production ◽

Additional Treatment ◽

Total Carbon ◽

Hydrocarbon Biodegradation ◽

Tundra Soil ◽

Spacer Length ◽

Freeze Thaw ◽

Arctic Tundra Soil

ABSTRACT Degradation of petroleum hydrocarbons was monitored in microcosms with diesel fuel-contaminated Arctic tundra soil incubated for 48 days at low temperatures (−5, 0, and 7°C). An additional treatment was incubation for alternating 24-h periods at 7 and −5°C. Hydrocarbons were biodegraded at or above 0°C, and freeze-thaw cycles may have actually stimulated hydrocarbon biodegradation. Total petroleum hydrocarbon (TPH) removal over 48 days in the 7, 0, and 7 and −5°C treatments, respectively, was 450, 300, and 600 μg/g of soil. No TPH removal was observed at −5°C. Total carbon dioxide production suggested that TPH removal was due to biological mineralization. Bacterial metabolic activity, indicated by RNA/DNA ratios, was higher in the middle of the experiment (day 21) than at the start, in agreement with measured hydrocarbon removal and carbon dioxide production activities. The total numbers of culturable heterotrophs and of hydrocarbon degraders did not change significantly over the 48 days of incubation in any of the treatments. At the end of the experiment, bacterial community structure, evaluated by ribosomal intergenic spacer length analysis, was very similar in all of the treatments but the alternating 7 and −5°C treatment.

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