Greenhouse gas budget (CO2, CH4and N2O) of intensively managed grassland following restoration

Merbold, Lutz; Eugster, Werner; Stieger, J.; Zahniser, M. S.; Nelson, David D.; Buchmann, Nina

doi:10.1111/gcb.12518

Cited by 172 publications

(115 citation statements)

References 61 publications

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“…4d). The repeating pattern of sign changes of NEP around grazing events is qualitatively similar to that shown by Merbold et al (2014) around harvests. Prior to grazing, daytime NEP was greater than 1 g C m −2 h −1 ; after grazing, daytime NEP became negative, typically for about three days, before returning to positive values.…”

Section: Nep and Et: Fluxes Annual Sums And Partitioningsupporting

confidence: 70%

“…6), indicated that the reduction of leaf area was followed by a drop and then a rise in production. This is typical of grassland sites with repeated grazing or harvest events (Wohlfahrt et al, 2008;Merbold et al, 2014). During the growing season, repeated defoliations kept the grass in a permanent juvenile state, which helped to maintain strong biomass growth throughout.…”

Section: Effects Of Management Practicesmentioning

confidence: 93%

“…Also, the effects of irrigation and fertiliser application on the carbon (C) budget are not clear. Greater GPP may lead to greater soil organic carbon (SOC) stocks, but for pasture, the transfer of atmospheric C to the SOC pool is largely dependent on grazing and irrigation management decisions (Ammann et al, 2007;Merbold et al, 2014). For some pastures, gains in GPP were offset by ecosystem respiration (ER) and C export (Ammann et al, 2007;Kelliher et al, 2012), so that a net loss of C and a negative net ecosystem carbon balance (NECB) resulted.…”

Section: Introductionmentioning

confidence: 99%

“…For some pastures, gains in GPP were offset by ecosystem respiration (ER) and C export (Ammann et al, 2007;Kelliher et al, 2012), so that a net loss of C and a negative net ecosystem carbon balance (NECB) resulted. For others, C inputs exceeded losses, leading to a positive NECB (Ammann et al, 2007;Merbold et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Carbon budgets for an irrigated intensively grazed dairy pasture and an unirrigated winter-grazed pasture

et al. 2016

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Abstract. Intensification of pastoral agriculture is occurring rapidly across New Zealand, including increasing use of irrigation and fertiliser application in some regions. While this enables greater gross primary production (GPP) and livestock grazing intensity, the consequences for the net ecosystem carbon budget (NECB) of the pastures are poorly known. Here, we determined the NECB over one year for an irrigated, fertilised and rotationally grazed dairy pasture and a neighbouring unirrigated, unfertilised, wintergrazed pasture. Primary terms in the NECB calculation were: net ecosystem production (NEP), biomass carbon removed by grazing cows and carbon (C) input from their excreta. Annual NEP was measured using the eddy-covariance method. Carbon removal was estimated with plate-meter measurements calibrated against biomass collections, preand post-grazing. Excreta deposition was calculated from animal feed intake. The intensively managed pasture gained C (NECB = 103 ± 42 g C m −2 yr −1 ) but would have been subject to a non-significant C loss if cattle excreta had not been returned to the pasture. The unirrigated pasture was C-neutral (NECB = −13 ± 23 g C m −2 yr −1 ). While annual GPP of the former was almost twice that of the latter (2679 vs. 1372 g C m −2 yr −1 ), ecosystem respiration differed by only 68 % between the two pastures (2271 vs. 1352 g C m −2 yr −1 ). The ratio of GPP to the total annual water input of the irrigated pasture was 37 % greater than that of the unirrigated pasture, i.e. the former used the water input more efficiently than the latter to produce biomass. The NECB results agree qualitatively with those from many other eddy-covariance studies of grazed grasslands, but they seem to be at odds with long-term carbon-stock studies of other New Zealand pastures.

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Section: Nep and Et: Fluxes Annual Sums And Partitioningsupporting

confidence: 70%

Section: Effects Of Management Practicesmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Carbon budgets for an irrigated intensively grazed dairy pasture and an unirrigated winter-grazed pasture

et al. 2016

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“…The eddy-covariance (EC) technique gives long-term, continuous, and spatially integrated measurements, which can fully capture FN2O. Advances in technology for N2O analyzers has increased the 10 number of long-term N2O measurement campaigns using EC methods (Mishurov and Kiely, 2010;Molodovskaya et al, 2012;Merbold et al, 2014;Huang et al, 2014;Rannik et al, 2015;Shurpali et al, 2016;Wang et al, 2016). However, the application has been limited to sites with high-quality power or short-term deployment.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a lower-powered analyser and sampling system for eddy-covariance measurements of nitrous oxide fluxes

Brown¹,

Sargent²,

Wagner‐Riddle³

2017

Preprint

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Abstract. Nitrous oxide (N2O) fluxes measured using the eddy-covariance method capture the spatial and temporal heterogeneity of N2O emissions. Most closed-path trace-gas analyzers for eddy-covariance measurements have large-volume, multi-pass absorption cells that necessitate high flow rates for ample frequency response, thus requiring high-power sample pumps. Other sampling system components, including rain caps, filters, dryers, and tubing can also degrade system frequency 10response. This field trial tested the performance of a closed-path eddy-covariance system for N2O flux measurements with improvements to use less power while maintaining the frequency response. The new system consists of a thermoelectrically cooled tunable diode laser absorption spectrometer configured to measure both N2O and carbon dioxide (CO2). The system features a relatively small, single-pass sample cell (200 ml) that provides good frequency response with a lower-powered pump (~250 W). A new filterless intake removes particulates from the sample air stream with no additional mixing volume that could 15 degrade frequency response. A single-tube dryer removes water vapor from the sample to avoid the need for density or spectroscopic corrections, while maintaining frequency response. This eddy-covariance system was collocated with a previous tunable diode laser absorption spectrometer model to compare N2O and CO2 flux measurements for two full growing seasons (May 2015 to October 2016) in a fertilized cornfield in Southern Ontario, Canada. Both spectrometers were placed outdoors at the base of the sampling tower demonstrating ruggedness for a range of environmental conditions (minimum to maximum 20 daily temperature range: -26.1 to 31.6°C). The new system rarely required maintenance. An in situ frequency response test demonstrated that the cutoff frequency of the new system was better than the old system (3.5 Hz compared to 2.30 Hz), and similar to that of a closed-path CO2 eddy-covariance system (4.05 Hz) using shorter tubing and no dryer that was also collocated at the site. Values of the N2O fluxes were similar between the two spectrometer systems (slope = 1.01, r 2 = 0.96); CO2 fluxes as measured by the short-tubed eddy-covariance system and the two spectrometer systems correlated well (slope = 25 1.03, r 2 = 0.998). The new lower-powered tunable diode laser absorption spectrometer configuration with the filterless intake and single-tube dryer showed promise for deployment in remote areas.Atmos. Meas. Tech. Discuss., https://doi

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Soil Moisture‐Temperature Coupling in a Set of Land Surface Models

Gevaert

Miralles

Jeu³

et al. 2018

JGR Atmospheres

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The land surface controls the partitioning of water and energy fluxes and therefore plays a crucial role in the climate system. The coupling between soil moisture and air temperature, in particular, has been shown to affect the severity and occurrence of temperature extremes and heat waves. Here we study soil moisture‐temperature coupling in five land surface models, focusing on the terrestrial segment of the coupling in the warm season. All models are run off‐line over a common period with identical atmospheric forcing data, in order to allow differences in the results to be attributed to the models' partitioning of energy and water fluxes. Coupling is calculated according to two semiempirical metrics, and results are compared to observational flux tower data. Results show that the locations of the global hot spots of soil moisture‐temperature coupling are similar across all models and for both metrics. In agreement with previous studies, these areas are located in transitional climate regimes. The magnitude and local patterns of model coupling, however, can vary considerably. Model coupling fields are compared to tower data, bearing in mind the limitations in the geographical distribution of flux towers and the differences in representative area of models and in situ data. Nevertheless, model coupling correlates in space with the tower‐based results ( r = 0.5–0.7), with the multimodel mean performing similarly to the best‐performing model. Intermodel differences are also found in the evaporative fractions and may relate to errors in model parameterizations and ancillary data of soil and vegetation characteristics.

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Greenhouse gas budget (CO₂, CH₄and N₂O) of intensively managed grassland following restoration

Cited by 172 publications

References 61 publications

Carbon budgets for an irrigated intensively grazed dairy pasture and an unirrigated winter-grazed pasture

Carbon budgets for an irrigated intensively grazed dairy pasture and an unirrigated winter-grazed pasture

Evaluation of a lower-powered analyser and sampling system for eddy-covariance measurements of nitrous oxide fluxes

Soil Moisture‐Temperature Coupling in a Set of Land Surface Models

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