scholarly journals The full greenhouse gas balance of an abandoned peat meadow

2007 ◽  
Vol 4 (3) ◽  
pp. 411-424 ◽  
Author(s):  
D. M. D. Hendriks ◽  
J. van Huissteden ◽  
A. J. Dolman ◽  
M. K. van der Molen
Keyword(s):  
Greenhouse Gas ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Co2 Uptake ◽  
Flux Chamber ◽  
Greenhouse Gas Balance ◽  
Dry Land ◽  
Ch4 Emissions ◽  
Growing Seasons ◽  
Ch4 And N2o

Abstract. Globally, peat lands are considered to be a sink of CO2, but a source when drained. Additionally, wet peat lands are thought to emit considerable amounts of CH4 and N2O. Hitherto, reliable and integrated estimates of emissions and emission factors for this type of land cover have been lacking and the effects of wetland restoration on methane emissions have been poorly quantified. In this paper we estimate the full greenhouse gas (GHG) balance of a restored natural peat land by determining the fluxes of CO2, CH4 and N2O through atmosphere and water, while accounting for the different Global Warming Potentials (GWP's). The site is an abandoned agricultural peat meadow, which has been converted into a wetland nature reserve ten years ago, after which the water level was raised. GHG fluxes were measured continuously with an eddy covariance system (CO2) and flux chamber measurements (CH4 and N2O). Meteorological and hydrological measurements were collected as well. With growing seasons of respectively 192, 168 and 129 days, the annual net ecosystem exchange of CO2 (NEE) was −446+±83 g C m−2 yr−1 for 2004, −311±58 g C m−2 yr−1 for 2005 and −232±57 g m−2 yr−1 for 2006. Ecosystem respiration (Reco) was estimated as 869±668 g C m−2 yr−1 for 2004, 866±666 g C m−2 yr−1 for 2005 and 924±711 g C m−2 yr−1 for 2006. CH4 emissions from the saturated land and water surfaces were high compared to the relatively dry land. Annual weighted CH4 emissions were 31.27±20.40 g C m−2 yr−1 for 2005 and 32.27±21.08 g C m−2 yr−1 for 2006. N2O fluxes were too low to be of significance. The water balance of the area was dominated by precipitation and evapotranspiration and therefore fluxes of carbon and CH4 through seepage, infiltration and drainage were relatively small (17.25 g C m−2 yr−1). The carbon-balance consisted for the largest part of CO2 uptake, CO2 respiration and CH4 emission from water saturated land and water. CO2 emission has decreased significantly as result of the raised water table, while CH4 fluxes have increased. In GWP's the area was a small net GHG sink given as CO2-equiv. of −86 g m−2 yr−1 (over a 100-year period).

scholarly journals The full greenhouse gas balance of an abandoned peat meadow

2007 ◽  
Vol 4 (1) ◽  
pp. 277-316 ◽  
Author(s):  
D. M. D. Hendriks ◽  
J. van Huissteden ◽  
A. J. Dolman ◽  
M. K. van der Molen
Keyword(s):  
Ecosystem Respiration ◽  
Eddy Correlation ◽  
Co2 Uptake ◽  
Ch4 Emission ◽  
Flux Chamber ◽  
Greenhouse Gas Balance ◽  
Dry Land ◽  
Growing Seasons ◽  
Ch4 And N2o ◽  
Water Saturated

Abstract. Globally, peat lands are considered to be a sink of CO2, but a source when drained. Additionally, wet peat lands are thought to emit considerable amounts of CH4 and N2O. Hitherto, reliable and integrated estimates of emissions and emission factors for this type of area have been lacking and the effects of wetland restoration on methane emissions have been poorly quantified. In this paper we estimate the full GHG balance of a restored natural peat land by determining the fluxes of CO2, CH4 and N2O through atmosphere and water, while accounting for the different GWP's. This site is an abandoned agricultural peat meadow, which has been converted into a wetland nature reserve ten years ago by raising the water level. GHG fluxes were measured continuously with an eddy-correlation system (CO2) and flux chamber measurements (CH4 and N2O). Meteorological and hydrological measurements were done as well. With growing seasons of respectively 192 and 155 days, the net annual CO2 uptake was 276±61 g C m−2 for 2004 and 311±58 g C m−2 for 2005. Ecosystem respiration was estimated as 887±668 g C m−2 for 2004 and 866±666 g C m−2 for 2005. CH4 fluxes from water, saturated land and relatively dry land varied: total annual CH4 fluxes are 10.4±19.2 g C m−2 yr−1, 101 g C m−2 yr−1±30 and 37.3±10.9 g C m−2 yr−1, respectively, and a annual weighed total CH4 emission of 31.27±20.44 g C m−2 yr−1. N2O fluxes were too low to be of significance. The carbon-balance consists for the largest part of CO2 uptake, CO2 respiration and CH4 emission from wet land and water. CO2 emission has decreased significantly as result of the raised water table, while CH4 fluxes have increased. In global warming potentials the area is a very small sink of 71 g CO2-equiv m−2 (over a 100-year period).

scholarly journals Greenhouse gas balance of cropland conversion to bioenergy poplar short-rotation coppice

2016 ◽  
Vol 13 (1) ◽  
pp. 95-113 ◽  
Author(s):  
S. Sabbatini ◽  
N. Arriga ◽  
T. Bertolini ◽  
S. Castaldi ◽  
T. Chiti ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Arable Land ◽  
Hybrid Poplar ◽  
Ghg Emissions ◽  
Net Ecosystem Exchange ◽  
Short Rotation Coppice ◽  
Co2 Uptake ◽  
Greenhouse Gas Balance ◽  
Short Rotation ◽  
Ch4 And N2o

Abstract. The production of bioenergy in Europe is one of the strategies conceived to reduce greenhouse gas (GHG) emissions. The suitability of the land use change from a cropland (REF site) to a short-rotation coppice plantation of hybrid poplar (SRC site) was investigated by comparing the GHG budgets of these two systems over 24 months in Viterbo, Italy. This period corresponded to a single rotation of the SRC site. The REF site was a crop rotation between grassland and winter wheat, i.e. the same management of the SRC site before the conversion to short-rotation coppice. Eddy covariance measurements were carried out to quantify the net ecosystem exchange of CO2 (FCO2), whereas chambers were used to measure N2O and CH4 emissions from soil. The measurements began 2 years after the conversion of arable land to SRC so that an older poplar plantation was used to estimate the soil organic carbon (SOC) loss due to SRC establishment and to estimate SOC recovery over time. Emissions from tractors and from production and transport of agricultural inputs (FMAN) were modelled. A GHG emission offset, due to the substitution of natural gas with SRC biomass, was credited to the GHG budget of the SRC site. Emissions generated by the use of biomass (FEXP) were also considered. Suitability was finally assessed by comparing the GHG budgets of the two sites. CO2 uptake was 3512 ± 224 g CO2 m−2 at the SRC site in 2 years, and 1838 ± 107 g CO2 m−2 at the REF site. FEXP was equal to 1858 ± 240 g CO2 m−2 at the REF site, thus basically compensating for FCO2, while it was 1118 ± 521 g CO2 m−2 at the SRC site. The SRC site could offset 379.7 ± 175.1 g CO2eq m−2 from fossil fuel displacement. Soil CH4 and N2O fluxes were negligible. FMAN made up 2 and 4 % in the GHG budgets of SRC and REF sites respectively, while the SOC loss was 455 ± 524 g CO2 m−2 in 2 years. Overall, the REF site was close to neutrality from a GHG perspective (156 ± 264 g CO2eq m−2), while the SRC site was a net sink of 2202 ± 792 g CO2eq m−2. In conclusion the experiment led to a positive evaluation from a GHG viewpoint of the conversion of cropland to bioenergy SRC.

scholarly journals Annual greenhouse gas budget for a bog ecosystem undergoing restoration by rewetting

2016 ◽  
Author(s):  
Sung Ching Lee ◽  
Andreas Christen ◽  
Andy T. Black ◽  
Mark S. Johnson ◽  
Rachhpal S. Jassal ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Water Table ◽  
Time Horizon ◽  
Ecosystem Respiration ◽  
High Water ◽  
Co2 Uptake ◽  
Raised Bog ◽  
Peat Mining ◽  
Ch4 Emissions ◽  
Carbon Dioxide Co2

Abstract. Many peatlands have been drained and harvested for peat mining, which has turned them from carbon (C) sinks into C emitters. Rewetting of disturbed peatlands facilitates their ecological recovery, and may help them revert to carbon dioxide (CO2) sinks. However, rewetting may also cause substantial emissions of the more potent greenhouse gas (GHG) methane (CH4). Our knowledge on the exchange of CO2 and CH4 following rewetting during restoration of disturbed peatlands is currently limited. This study quantifies annual fluxes of CO2 and CH4 in a disturbed and rewetted area located in the Burns Bog Ecological Conservancy Area in Delta, BC, Canada. Burns Bog is recognized as the largest raised bog ecosystem on North America's West Coast. Burns Bog was substantially reduced in size and degraded by peat mining and agriculture. Since 2005, the bog has been declared a conservancy area, with restoration efforts focusing on rewetting disturbed ecosystems to recover Sphagnum and suppress fires. Using the eddy-covariance (EC) technique, we measured year-round (16th June 2015 to 15th June 2016) turbulent fluxes of CO2 and CH4 from a tower platform in an area rewetted for the last 8 years. The study area, dominated by sedges and Sphagnum, experienced a varying water table position that ranged between 7.7 (inundation) and −26.5 cm from the surface during the study year. The annual CO2 budget of the rewetted area was −179 g CO2-C m−2 year−1 (CO2 sink) and the annual CH4 budget was 16 g CH4-C m−2 year−1 (CH4 source). Gross ecosystem productivity (GEP) exceeded ecosystem respiration (Re) during summer months (June–August), causing a net CO2 uptake. In summer, high CH4 emissions (121 mg CH4-C m−2 day−1) were measured. In winter (December–February), while roughly equal magnitudes of GEP and Re made the study area CO2 neutral, very low CH4 emissions (9 mg CH4-C m−2 day−1) were observed. The key environmental factors controlling the seasonality of these exchanges were downwelling photosynthetically active radiation and 5-cm soil temperature. It appears that the high water table caused by ditch blocking which suppresses Re. With low temperatures in winter, CH4 emission was more suppressed than Re. Annual net GHG flux from CO2 and CH4 expressed in terms of CO2 equivalents (CO2e) during the study period totaled to −55 g CO2e m−2 year−1 (net CO2e sink) and 1147 g CO2e m−2 year−1 (net CO2e source) by using 100-year and 20-year global warming potential values, respectively. Consequently, the ecosystem was almost CO2e neutral during the study period expressed on a 100-year time horizon but was a significant CO2e source on a 20-year time horizon.

scholarly journals Carbon dioxide and methane exchange of a patterned subarctic fen during two contrasting growing seasons

2021 ◽  
Vol 18 (3) ◽  
pp. 873-896
Author(s):  
Lauri Heiskanen ◽  
Juha-Pekka Tuovinen ◽  
Aleksi Räsänen ◽  
Tarmo Virtanen ◽  
Sari Juutinen ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ecosystem Respiration ◽  
Growing Season ◽  
Drought Event ◽  
Flux Chamber ◽  
Ch4 Emissions ◽  
Growing Seasons ◽  
Ecosystem Level ◽  
Community Types ◽  
Carbon Dioxide Co2

Abstract. The patterned microtopography of subarctic mires generates a variety of environmental conditions, and carbon dioxide (CO2) and methane (CH4) dynamics vary spatially among different plant community types (PCTs). We studied the CO2 and CH4 exchange between a subarctic fen and the atmosphere at Kaamanen in northern Finland based on flux chamber and eddy covariance measurements in 2017–2018. We observed strong spatial variation in carbon dynamics between the four main PCTs studied, which were largely controlled by water table level and differences in vegetation composition. The ecosystem respiration (ER) and gross primary productivity (GPP) increased gradually from the wettest PCT to the drier ones, and both ER and GPP were larger for all PCTs during the warmer and drier growing season 2018. We estimated that in 2017 the growing season CO2 balances of the PCTs ranged from −20 g C m−2 (Trichophorum tussock PCT) to 64 g C m−2 (string margin PCT), while in 2018 all PCTs were small CO2 sources (10–22 g C m−2). We observed small growing season CH4 emissions (< 1 g C m−2) from the driest PCT, while the other three PCTs had significantly larger emissions (mean 7.9, range 5.6–10.1 g C m−2) during the two growing seasons. Compared to the annual CO2 balance (−8.5 ± 4.0 g C m−2) of the fen in 2017, in 2018 the annual balance (−5.6 ± 3.7 g C m−2) was affected by an earlier onset of photosynthesis in spring, which increased the CO2 sink, and a drought event during summer, which decreased the sink. The CH4 emissions were also affected by the drought. The annual CH4 balance of the fen was 7.3 ± 0.2 g C m−2 in 2017 and 6.2 ± 0.1 g C m−2 in 2018. Thus, the carbon balance of the fen was close to zero in both years. The PCTs that were adapted to drier conditions provided ecosystem-level resilience to carbon loss due to water level drawdown.

scholarly journals Exchange of CO<sub>2</sub> in Arctic tundra: impacts of meteorological variations and biological disturbance

2016 ◽  
Author(s):  
Efrén López-Blanco ◽  
Magnus Lund ◽  
Mathew Williams ◽  
Mikkel P. Tamstorf ◽  
Andreas Westergaard-Nielsen ◽  
...  
Keyword(s):  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Variable Coefficients ◽  
The Arctic ◽  
Sink Strength ◽  
Co2 Uptake ◽  
Growing Seasons ◽  
Meteorological Effect ◽  
Major Pest

Abstract. An improvement in our process-based understanding of carbon (C) exchange in the Arctic, and its climate sensitivity, is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analyzed the net ecosystem exchange (NEE) of CO2 in West Greenland tundra (64° N) across eight snow-free periods in eight consecutive years, and characterized the key processes of net ecosystem exchange, and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO2, accumulating −30 g C m−2 on average (range −17 to −41 g C m−2) during the years 2008–2015, except 2011 that was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high inter-annual variability in the timing of snowmelt, start and duration of the growing season. The ranges in annual GPP (−182 to −316 g C m−2) and Reco (144 to 279 g C m−2) were > 5 fold larger and they were also more variable (Coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and Reco were sensitive to insolation and temperatures; and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to climate was a result of the correlated meteorological response of GPP and Reco. During the 2011 anomalous year, the studied ecosystem released 41 g C m−2 as biological disturbance reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling although shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge the forecast of upcoming C states.

scholarly journals Exchange of CO<sub>2</sub> in Arctic tundra: impacts of meteorological variations and biological disturbance

2017 ◽  
Vol 14 (19) ◽  
pp. 4467-4483 ◽  
Author(s):  
Efrén López-Blanco ◽  
Magnus Lund ◽  
Mathew Williams ◽  
Mikkel P. Tamstorf ◽  
Andreas Westergaard-Nielsen ◽  
...  
Keyword(s):  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Variable Coefficients ◽  
The Arctic ◽  
Correlated Response ◽  
Sink Strength ◽  
Co2 Uptake ◽  
Growing Seasons ◽  
Major Pest

Abstract. An improvement in our process-based understanding of carbon (C) exchange in the Arctic and its climate sensitivity is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analysed the net ecosystem exchange (NEE) of CO2 in West Greenland tundra (64° N) across eight snow-free periods in 8 consecutive years, and characterized the key processes of net ecosystem exchange and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO2, accumulating −30 g C m−2 on average (range of −17 to −41 g C m−2) during the years 2008–2015, except 2011 (source of 41 g C m−2), which was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high interannual variability in the timing of snowmelt and the start and duration of the growing season. The ranges in annual GPP (−182 to −316 g C m−2) and Reco (144 to 279 g C m−2) were  > 5 fold larger than the range in NEE. Gross fluxes were also more variable (coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and Reco were sensitive to insolation and temperature, and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to meteorology was a result of the correlated response of GPP and Reco. During the snow-free season of the anomalous year of 2011, a biological disturbance related to a larvae outbreak reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling. However, shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge our forecasting of C states.

scholarly journals Annual greenhouse gas budget for a bog ecosystem undergoing restoration by rewetting

2017 ◽  
Vol 14 (11) ◽  
pp. 2799-2814 ◽  
Author(s):  
Sung-Ching Lee ◽  
Andreas Christen ◽  
Andrew T. Black ◽  
Mark S. Johnson ◽  
Rachhpal S. Jassal ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Water Table ◽  
Time Horizon ◽  
Ecosystem Respiration ◽  
High Water ◽  
Co2 Uptake ◽  
Raised Bog ◽  
Peat Mining ◽  
Ch4 Emissions ◽  
Carbon Dioxide Co2

Abstract. Many peatlands have been drained and harvested for peat mining, agriculture, and other purposes, which has turned them from carbon (C) sinks into C emitters. Rewetting of disturbed peatlands facilitates their ecological recovery and may help them revert to carbon dioxide (CO2) sinks. However, rewetting may also cause substantial emissions of the more potent greenhouse gas (GHG) methane (CH4). Our knowledge of the exchange of CO2 and CH4 following rewetting during restoration of disturbed peatlands is currently limited. This study quantifies annual fluxes of CO2 and CH4 in a disturbed and rewetted area located in the Burns Bog Ecological Conservancy Area in Delta, BC, Canada. Burns Bog is recognized as the largest raised bog ecosystem on North America's west coast. Burns Bog was substantially reduced in size and degraded by peat mining and agriculture. Since 2005, the bog has been declared a conservancy area, with restoration efforts focusing on rewetting disturbed ecosystems to recover Sphagnum and suppress fires. Using the eddy covariance (EC) technique, we measured year-round (16 June 2015 to 15 June 2016) turbulent fluxes of CO2 and CH4 from a tower platform in an area rewetted for the last 8 years. The study area, dominated by sedges and Sphagnum, experienced a varying water table position that ranged between 7.7 (inundation) and −26.5 cm from the surface during the study year. The annual CO2 budget of the rewetted area was −179 ± 26.2 g CO2–C m−2 yr−1 (CO2 sink) and the annual CH4 budget was 17 ± 1.0 g CH4–C m−2 yr−1 (CH4 source). Gross ecosystem productivity (GEP) exceeded ecosystem respiration (Re) during summer months (June–August), causing a net CO2 uptake. In summer, high CH4 emissions (121 mg CH4–C m−2 day−1) were measured. In winter (December–February), while roughly equal magnitudes of GEP and Re made the study area CO2 neutral, very low CH4 emissions (9 mg CH4–C m−2 day−1) were observed. The key environmental factors controlling the seasonality of these exchanges were downwelling photosynthetically active radiation and 5 cm soil temperature. It appears that the high water table caused by ditch blocking suppressed Re. With low temperatures in winter, CH4 emissions were more suppressed than Re. Annual net GHG flux from CO2 and CH4 expressed in terms of CO2 equivalents (CO2 eq.) during the study period totalled −22 ± 103.1 g CO2 eq. m−2 yr−1 (net CO2 eq. sink) and 1248 ± 147.6 g CO2 eq. m−2 yr−1 (net CO2 eq. source) by using 100- and 20-year global warming potential values, respectively. Consequently, the ecosystem was almost CO2 eq. neutral during the study period expressed on a 100-year time horizon but was a significant CO2 eq. source on a 20-year time horizon.

scholarly journals Comparison of soil greenhouse gas fluxes from extensive and intensive grazing in a temperate maritime climate

2012 ◽  
Vol 9 (8) ◽  
pp. 10057-10085
Author(s):  
U. Skiba ◽  
S. K. Jones ◽  
J. Drewer ◽  
C. Helfter ◽  
M. Anderson ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Net Ecosystem Exchange ◽  
Ground Vegetation ◽  
Co2 Uptake ◽  
Gas Fluxes ◽  
Greenhouse Gas Fluxes ◽  
Temperature Radiation ◽  
Ch4 And N2o ◽  
Ghg Fluxes ◽  
Grazed Grassland

Abstract. Greenhouse gas (GHG) fluxes from a seminatural, extensively sheep grazed drained moorland and intensively sheep grazed fertilised grassland in SE Scotland were compared over 4 yr (2007–2010). Nitrous oxide and CH4 fluxes were measured by static chambers, respiration from soil including ground vegetation by a flow through chamber and the net ecosystem exchange of CO2 by eddy covariance. All GHG fluxes displayed high temporal and interannual variability. Temperature, radiation, water table height and precipitation could explain a significant percentage of seasonal and interannual variations. Greenhouse gas fluxes were dominated by the net ecosystem exchange of CO2, emissions of N2O from the grazed grassland (384 g CO2eq m−2 yr−1) and emissions of CH4 from ruminant fermentation (147 g CO2eq m−2 yr−1). Methane emissions from the moorland were small (6.7 g CO2eq m−2 yr−1). Net ecosystem exchange of CO2 and respiration were much larger on the productive fertilised grassland (−1624 and +7157 g CO2eq m−2 yr−1, respectively) than the seminatural moorland (−338 and +2554 g CO2eq m−2 yr−1, respectively). Large CH4 and N2O losses from the grazed grassland counteracted the CO2 uptake by 35%, whereas the small N2O and CH4 emissions from the moorland did only impact the NEE by 2%.The 4 yr average GHG budget for the grazed grassland was 1006 g CO2eq m−2 yr−1 and 331 g CO2eq m−2 yr−1 for the moorland.

scholarly journals Greenhouse gas flux measurements in a forestry-drained peatland indicate a large carbon sink

2011 ◽  
Vol 8 (11) ◽  
pp. 3203-3218 ◽  
Author(s):  
A. Lohila ◽  
K. Minkkinen ◽  
M. Aurela ◽  
J.-P. Tuovinen ◽  
T. Penttilä ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Accumulation Rate ◽  
Peat Soil ◽  
Net Ecosystem Exchange ◽  
Flux Measurement ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Flux Measurements ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) change: due to the accelerated decomposition of peat in the presence of oxygen, drained peatlands are generally considered to lose peat carbon (C). We measured CO2 exchange with the eddy covariance (EC) method above a drained nutrient-poor peatland forest in southern Finland for 16 months in 2004–2005. The site, classified as a dwarf-shrub pine bog, had been ditched about 35 years earlier. CH4 and N2O fluxes were measured at 2–5-week intervals with the chamber technique. Drainage had resulted in a relatively little change in the water table level, being on average 40 cm below the ground in 2005. The annual net ecosystem exchange was −870 ± 100 g CO2 m−2 yr−1 in the calendar year 2005, indicating net CO2 uptake from the atmosphere. The site was a small sink of CH4 (−0.12 g CH4 m−2 yr−1) and a small source of N2O (0.10 g N2O m−2 yr−1). Photosynthesis was detected throughout the year when the air temperature exceeded −3 °C. As the annual accumulation of C in the above and below ground tree biomass (175 ± 35 g C m−2) was significantly lower than the accumulation observed by the flux measurement (240 ± 30 g C m−2), about 65 g C m−2 yr−1 was likely to have accumulated as organic matter into the peat soil. This is a higher average accumulation rate than previously reported for natural northern peatlands, and the first time C accumulation has been shown by EC measurements to occur in a forestry-drained peatland. Our results suggest that forestry-drainage may significantly increase the CO2 uptake rate of nutrient-poor peatland ecosystems.

scholarly journals Delayed responses of an Arctic ecosystem to an extreme summer: impacts on net ecosystem exchange and vegetation functioning

2014 ◽  
Vol 11 (20) ◽  
pp. 5877-5888 ◽  
Author(s):  
D. Zona ◽  
D. A. Lipson ◽  
J. H. Richards ◽  
G. K. Phoenix ◽  
A. K. Liljedahl ◽  
...  
Keyword(s):  
Extreme Events ◽  
Extreme Event ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Co2 Uptake ◽  
Lag Effects ◽  
Tundra Ecosystem ◽  
Co2 Sink ◽  
The Impact

Abstract. The importance and consequences of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. In the summer of 2007 in Barrow, Arctic Alaska, there were unusually high air temperatures (the fifth warmest summer over a 65-year period) and record low precipitation (the lowest over a 65-year period). These abnormal conditions were associated with substantial desiccation of the Sphagnum layer and a reduced net Sphagnum CO2 sink but did not affect net ecosystem exchange (NEE) from this wet-sedge arctic tundra ecosystem. Microbial biomass, NH4+ availability, gross primary production (GPP), and ecosystem respiration (Reco) were generally greater during this extreme summer. The cumulative ecosystem CO2 sink in 2007 was similar to the previous summers, suggesting that vascular plants were able to compensate for Sphagnum CO2 uptake, despite the impact on other functions and structure such as desiccation of the Sphagnum layer. Surprisingly, the lowest ecosystem CO2 sink over a five summer record (2005–2009) was observed during the 2008 summer (~70% lower), directly following the unusually warm and dry summer, rather than during the extreme summer. This sink reduction cannot solely be attributed to the potential damage to mosses, which typically contribute ~40% of the entire ecosystem CO2 sink. Importantly, the return to a substantial cumulative CO2 sink occurred two summers after the extreme event, which suggests a substantial resilience of this tundra ecosystem to at least an isolated extreme event. Overall, these results show a complex response of the CO2 sink and its sub-components to atypically warm and dry conditions. The impact of multiple extreme events requires further investigation.

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