scholarly journals Are there memory effects on greenhouse gas emissions (CO<sub>2</sub>, N<sub>2</sub>O and CH<sub>4</sub>) following grassland restoration?

2021 ◽  
Vol 18 (4) ◽  
pp. 1481-1498
Author(s):  
Lutz Merbold ◽  
Charlotte Decock ◽  
Werner Eugster ◽  
Kathrin Fuchs ◽  
Benjamin Wolf ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Eddy Covariance ◽  
Organic Fertilizer ◽  
Memory Effects ◽  
Process Models ◽  
Grassland Restoration ◽  
Co2 Uptake ◽  
Static Chamber ◽  
Sequestration Potential ◽  
Ch4 And N2o

Abstract. A 5-year greenhouse gas (GHG) exchange study of the three major gas species (CO2, CH4 and N2O) from an intensively managed permanent grassland in Switzerland is presented. Measurements comprise 2 years (2010 and 2011) of manual static chamber measurements of CH4 and N2O, 5 years of continuous eddy covariance (EC) measurements (CO2–H2O – 2010–2014), and 3 years (2012–2014) of EC measurement of CH4 and N2O. Intensive grassland management included both regular and sporadic management activities. Regular management practices encompassed mowing (three to five cuts per year) with subsequent organic fertilizer amendments and occasional grazing, whereas sporadic management activities comprised grazing or similar activities. The primary objective of our measurements was to compare pre-plowing to post-plowing GHG exchange and to identify potential memory effects of such a substantial disturbance on GHG exchange and carbon (C) and nitrogen (N) gains and losses. In order to include measurements carried out with different observation techniques, we tested two different measurement techniques jointly in 2013, namely the manual static chamber approach and the eddy covariance technique for N2O, to quantify the GHG exchange from the observed grassland site. Our results showed that there were no memory effects on N2O and CH4 emissions after plowing, whereas the CO2 uptake of the site considerably increased when compared to pre-restoration years. In detail, we observed large losses of CO2 and N2O during the year of restoration. In contrast, the grassland acted as a carbon sink under usual management, i.e., the time periods 2010–2011 and 2013–2014. Enhanced emissions and emission peaks of N2O (defined as exceeding background emissions 0.21 ± 0.55 nmol m−2 s−1 (SE = 0.02) for at least 2 sequential days and the 7 d moving average exceeding background emissions) were observed for almost 7 continuous months after restoration as well as following organic fertilizer applications during all years. Net ecosystem exchange of CO2 (NEECO2) showed a common pattern of increased uptake of CO2 in spring and reduced uptake in late fall. NEECO2 dropped to zero and became positive after each harvest event. Methane (CH4) exchange fluctuated around zero during all years. Overall, CH4 exchange was of negligible importance for both the GHG budget and the carbon budget of the site. Our results stress the inclusion of grassland restoration events when providing cumulative sums of C sequestration potential and/or global warming potential (GWP). Consequently, this study further highlights the need for continuous long-term GHG exchange observations as well as for the implementation of our findings into biogeochemical process models to track potential GHG mitigation objectives as well as to predict future GHG emission scenarios reliably.

scholarly journals Memory effects on greenhouse gas emissions (CO<sub>2</sub>, N<sub>2</sub>O and CH<sub>4</sub>) following grassland restoration?

2020 ◽  
Author(s):  
Lutz Merbold ◽  
Charlotte Decock ◽  
Werner Eugster ◽  
Kathrin Fuchs ◽  
Benjamin Wolf ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Eddy Covariance ◽  
Organic Fertilizer ◽  
Measurement Techniques ◽  
Memory Effects ◽  
Process Models ◽  
Grassland Restoration ◽  
Co2 Uptake ◽  
Static Chamber ◽  
Ch4 And N2o

Abstract. A five-year greenhouse gas (GHG) exchange study of the three major gas species (CO2, CH4 and N2O) from an intensively managed permanent grassland in Switzerland is presented. Measurements comprise two years (2010/2011) of manual static chamber measurements of CH4 and N2O, five years of continuous eddy covariance (EC) measurements (CO2/H2O – 2010–2014) and three years (2012–2014) of EC measurement of CH4 and N2O. Intensive grassland management included both regular and sporadic management activities. Regular management practices encompassed mowing (3–5 cuts per year) with subsequent organic fertilizer amendments and occasional grazing whereas sporadic management activities comprised grazing or similar activities. The primary objective of our measurements was to compare pre-ploughing to post-ploughing GHG exchange and to identify potential memory effects of such a substantial disturbance on GHG exchange and carbon (C) and nitrogen (N) budgets. In order to include measurements carried with different observation techniques, we tested two different measurement techniques jointly in 2013, namely the manual static chamber approach and the eddy covariance technique, to quantify the GHG exchange from the observed grassland site. Our results showed that there were no memory effects on N2O and CH4 emissions after ploughing, whereas the CO2 uptake of the site considerably increased when compared to post-restoration years. In detail, we observed large losses of CO2 and N2O during the year of restoration. In contrast, the grassland acted as a carbon sink under usual management, i.e. the time periods (2010–2011 and 2013–2014). Enhanced emissions/emission peaks of N2O (defined as exceeding background emissions < 0.21 ± 0.55 nmol m−2s−1 (SE = 0.02) for at least two sequential days and the seven-day moving average exceeding background emissions) were observed for almost seven continuous months after restoration as well following organic fertilizer applications during all. Net ecosystem exchange of CO2 (NEECO2) showed a common pattern of increased uptake of CO2 in spring and reduced uptake in late fall. NEECO2 dropped to zero and became positive after each harvest event. Methane (CH4) exchange in contrast to N2O showed minor net uptake of methane seen by the static chambers and small net release of methane seen by the eddy covariance method. Overall, CH4 exchange was of negligible importance for both, the GHG budget as well as for the carbon budget of the site. Our results stress the inclusion of grassland restoration events when providing cumulative sums of C sequestration and/or global warming potentials (GWPs). Consequently, this study further highlights the need for continuous long-term GHG exchange observations as well as the implementation of our findings into biogeochemical process models to track potential GHG mitigation objectives as well as to predict future GHG emission scenarios reliably.

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 North American terrestrial CO2 uptake largely offset by CH4 and N2O emissions: toward a full accounting of the greenhouse gas budget

2014 ◽  
Vol 129 (3-4) ◽  
pp. 413-426 ◽  
Author(s):  
Hanqin Tian ◽  
Guangsheng Chen ◽  
Chaoqun Lu ◽  
Xiaofeng Xu ◽  
Daniel J. Hayes ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
North American ◽  
N2o Emissions ◽  
Co2 Uptake ◽  
Greenhouse Gas Budget ◽  
Ch4 And N2o

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 Estimating greenhouse gas fluxes from an agriculture-dominated landscape using multiple planetary boundary layer methods

2014 ◽  
Vol 14 (3) ◽  
pp. 3231-3267 ◽  
Author(s):  
X. Zhang ◽  
X. Lee ◽  
T. J. Griffis ◽  
J. M. Baker ◽  
W. Xiao
Keyword(s):  
Greenhouse Gas ◽  
Eddy Covariance ◽  
Co2 Flux ◽  
N2o Emissions ◽  
Top Down ◽  
Equilibrium Method ◽  
Flux Aggregation ◽  
Ch4 And N2o ◽  
Ghg Fluxes ◽  
Tall Tower

Abstract. Quantification of regional greenhouse gas (GHG) fluxes is essential for establishing mitigation strategies and evaluating their effectiveness. Here, we used multiple top-down approaches and multiple trace gas observations at a tall tower to estimate GHG regional fluxes and evaluate the GHG fluxes derived from bottom-up approaches. We first applied the eddy covariance, equilibrium, inverse modeling (CarbonTracker), and flux aggregation methods using three years of carbon dioxide (CO2) measurements on a 244 m tall tower in the Upper Midwest, USA. We then applied the equilibrium method for estimating methane (CH4) and nitrous oxide (N2O) fluxes with one-month high-frequency CH4 and N2O gradient measurements on the tall tower and one-year concentration measurements on a nearby tall tower, and evaluated the uncertainties of this application. The results indicate that: (1) the flux aggregation, eddy covariance, the equilibrium method, and the CarbonTracker product all gave similar seasonal patterns of the regional CO2 flux (105–106 km2), but that the equilibrium method underestimated the July CO2 flux by 52–69%. (2) The annual budget varied among these methods from 74 to −131 g C-CO2 m−2 yr−1, indicating a large uncertainty in the annual CO2 flux estimation. (3) The regional CH4 and N2O emissions according to a top-down method were at least six and two times higher than the emissions from a bottom-up inventory (Emission Database for Global Atmospheric Research), respectively. (4) The global warming potentials of the CH4 and N2O emissions were equal in magnitude to the cooling benefit of the regional CO2 uptake. The regional GHG budget, including both biological and anthropogenic origins, is estimated at 7 ± 160 g CO2 eq m−2 yr−1.

scholarly journals The greenhouse gas balance of European grasslands

2010 ◽  
Vol 7 (4) ◽  
pp. 5997-6050 ◽  
Author(s):  
P. Ciais ◽  
J. F. Soussana ◽  
N. Vuichard ◽  
S. Luyssaert ◽  
A. Don ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Eddy Covariance ◽  
Net Primary Productivity ◽  
Carbon Sink ◽  
Management Practice ◽  
Carbon Sinks ◽  
Forage Production ◽  
Greenhouse Gas Balance ◽  
Ch4 And N2o ◽  
Gas Balance

Abstract. The long-term carbon balance (NBP) of grasslands is estimated by combining scarce multi-year eddy-covariance observations at ecosystem observation sites where information on carbon inputs and harvesting removals is available. Following accounting for carbon leached to rivers, we estimated grasslands to be net carbon sinks of 74±10 g C m−2 yr−1. Uncertainties arise from the small number of sites and the short measurement period. Only 11 sites, out of a total of 20 grassland sites in Europe where eddy covariance systems are installed, were set-up for estimating NBP. These 11 selected sites are representative of intensive management practice and we lack information on disturbance history, such as plowing. This suggests that the grassland NBP estimate is likely biased towards overestimating the sink, compared to the European average. Direct measurements of Net Primary Productivity (NPP) are not possible in grasslands given permanent biomass removal by grazing and mowing, uncertainties in rhizodeposition and production of volatile organic carbon compounds lost to the atmosphere. Therefore, the grassland process-based ecosystem model PASIM was used to estimate the spatial-temporal distribution of NPP, providing a European average value of 750±150 g C across extensively grazed, intensively grazed pastures, and forage production systems. In Europe the NPP of grasslands seems higher than that of croplands and forests. The carbon sequestration efficiency of grasslands, defined as the ratio of NBP to NPP, amounts to 0.09±0.10. Therefore, per unit of carbon input, grasslands sequester 3–4 times more carbon in the soil than forests do, making them a good candidate for managing onsite carbon sinks. When using the 100 yr greenhouse warming potential for CH4 and N2O, their emissions due to management of grasslands together offset roughly 70–80% of the carbon sink. Uncertainties on the European grassland greenhouse gas balance, including CO2, CH4 and N2O fluxes are likely to be reduced in the near future, with data being collected from more sites, and improved up-scaling methods.

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 Effects of land use intensity on the full greenhouse gas balance in an Atlantic peat bog

2013 ◽  
Vol 10 (2) ◽  
pp. 1067-1082 ◽  
Author(s):  
S. Beetz ◽  
H. Liebersbach ◽  
S. Glatzel ◽  
G. Jurasinski ◽  
U. Buczko ◽  
...  
Keyword(s):  
Land Use ◽  
Gas Exchange ◽  
Greenhouse Gas ◽  
Peat Bog ◽  
Northwest Germany ◽  
Natural Site ◽  
Sequestration Potential ◽  
Average Annual Temperature ◽  
N2o Fluxes ◽  
Ch4 And N2o

Abstract. Wetlands can either be net sinks or net sources of greenhouse gases (GHGs), depending on the mean annual water level and other factors like average annual temperature, vegetation development, and land use. Whereas drained and agriculturally used peatlands tend to be carbon dioxide (CO2) and nitrous oxide (N2O) sources but methane (CH4) sinks, restored (i.e. rewetted) peatlands rather incorporate CO2, tend to be N2O neutral and release CH4. One of the aims of peatland restoration is to decrease their global warming potential (GWP) by reducing GHG emissions. We estimated the greenhouse gas exchange of a peat bog restoration sequence over a period of 2 yr (1 July 2007–30 June 2009) in an Atlantic raised bog in northwest Germany. We set up three study sites representing different land use intensities: intensive grassland (deeply drained, mineral fertilizer, cattle manure and 4–5 cuts per year); extensive grassland (rewetted, no fertilizer or manure, up to 1 cutting per year); near-natural peat bog (almost no anthropogenic influence). Daily and annual greenhouse gas exchange was estimated based on closed-chamber measurements. CH4 and N2O fluxes were recorded bi-weekly, and net ecosystem exchange (NEE) measurements were carried out every 3–4 weeks. Annual sums of CH4 and N2O fluxes were estimated by linear interpolation while NEE was modelled. Regarding GWP, the intensive grassland site emitted 564 ± 255 g CO2–C equivalents m−2 yr−1 and 850 ± 238 g CO2–C equivalents m−2 yr−1 in the first (2007/2008) and the second (2008/2009) measuring year, respectively. The GWP of the extensive grassland amounted to −129 ± 231 g CO2–C equivalents m−2 yr−1 and 94 ± 200 g CO2–C equivalents m−2 yr−1, while it added up to 45 ± 117 g CO2–C equivalents m−2 yr−1 and −101 ± 93 g CO2–C equivalents m−2 yr−1 in 2007/08 and 2008/09 for the near-natural site. In contrast, in calendar year 2008 GWP aggregated to 441 ± 201 g CO2–C equivalents m−2 yr−1, 14 ± 162 g CO2–C equivalents m−2 yr−1 and 31 ± 75 g CO2–C equivalents m−2 yr−1 for the intensive grassland, extensive grassland, and near-natural site, respectively. Despite inter-annual variability, rewetting contributes considerably to mitigating GHG emission from formerly drained peatlands. Extensively used grassland on moderately drained peat approaches the carbon sequestration potential of near-natural sites, although it may oscillate between being a small sink and being a small source depending on inter-annual climatic variability.

scholarly journals Eddy covariance flux measurements confirm extreme CH<sub>4</sub> emissions from a Swiss hydropower reservoir and resolve their short-term variability

2011 ◽  
Vol 8 (9) ◽  
pp. 2815-2831 ◽  
Author(s):  
W. Eugster ◽  
T. DelSontro ◽  
S. Sobek
Keyword(s):  
Greenhouse Gas ◽  
Eddy Covariance ◽  
Land Surface ◽  
Lake Level ◽  
Driving Forces ◽  
Open Water ◽  
Short Term ◽  
Flux Measurements ◽  
Floating Chamber ◽  
Hydropower Reservoir

Abstract. Greenhouse gas budgets quantified via land-surface eddy covariance (EC) flux sites differ significantly from those obtained via inverse modeling. A possible reason for the discrepancy between methods may be our gap in quantitative knowledge of methane (CH4) fluxes. In this study we carried out EC flux measurements during two intensive campaigns in summer 2008 to quantify methane flux from a hydropower reservoir and link its temporal variability to environmental driving forces: water temperature and pressure changes (atmospheric and due to changes in lake level). Methane fluxes were extremely high and highly variable, but consistently showed gas efflux from the lake when the wind was approaching the EC sensors across the open water, as confirmed by floating chamber flux measurements. The average flux was 3.8 ± 0.4 μg C m−2 s−1 (mean ± SE) with a median of 1.4 μg C m−2 s−1, which is quite high even compared to tropical reservoirs. Floating chamber fluxes from four selected days confirmed such high fluxes with 7.4 ± 1.3 μg C m−2 s−1. Fluxes increased exponentially with increasing temperatures, but were decreasing exponentially with increasing atmospheric and/or lake level pressure. A multiple regression using lake surface temperatures (0.1 m depth), temperature at depth (10 m deep in front of the dam), atmospheric pressure, and lake level was able to explain 35.4% of the overall variance. This best fit included each variable averaged over a 9-h moving window, plus the respective short-term residuals thereof. We estimate that an annual average of 3% of the particulate organic matter (POM) input via the river is sufficient to sustain these large CH4 fluxes. To compensate the global warming potential associated with the CH4 effluxes from this hydropower reservoir a 1.3 to 3.7 times larger terrestrial area with net carbon dioxide uptake is needed if a European-scale compilation of grasslands, croplands and forests is taken as reference. This indicates the potential relevance of temperate reservoirs and lakes in local and regional greenhouse gas budgets.

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