Modelling carbon and water exchange of a grazed pasture in New Zealand constrained by eddy covariance measurements

Kirschbaum, Miko U. F.; Rutledge, Susanna; Kuijper, Isoude A.; Mudge, Paul L.; Puche, Nicolas; Wall, Aaron M.; Roach, C. G.; Schipper, Louis A.; Campbell, David I.

doi:10.1016/j.scitotenv.2015.01.045

Cited by 34 publications

(22 citation statements)

References 62 publications

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“…For the present work, we used CenW version 4.2, which is available for download, together with its source code and a list of relevant equations available in cenW documentation, version 4.1.1 (A growth and C balance simulation model, © 2017). A number of additional routines were added to run the model for managed pastures [56]. A list of relevant parameters is given in Appendix B.…”

Section: Cenw 42 Overviewmentioning

confidence: 99%

“…It was important to model these processes as the estimates of foliage biomass included a component of dead standing biomass that was not separated out in the data. These processes were modeled by assuming that all senescence, or drought-induced leaf death, initially transferred foliage from a live to a dead foliage pool [56]. The soil is divided into multiple layers and the same calculations driving the behavior of organic matter are applied to all of them, with each layer having its own complement of all organic matter pools.…”

Section: Cenw 42 Overviewmentioning

confidence: 99%

“…To effectively model net carbon fluxes in a managed pasture system, it was essential to know the timing of grazing, feed supplementation, and harvesting carried out on each paddock [56]. For the "grazed" paddock of the Lusignan study farm described above, the model assumed (similar to the study of a dairy farm in New Zealand [56]) that cows consumed, at each grazing event, a given amount of above ground biomass [74]. If grazing was spread over several consecutive days, grazing percentages on individual days were adjusted to add to a total of that fixed percentage at the end of the grazing events.…”

Section: Cenw 42 Overviewmentioning

confidence: 99%

“…The soil organic matter module of the model was derived from the CENTURY model [55], which was originally developed for grasslands (more details are given in Section 2.2). Recently, CenW was successfully parameterized and used to simulate carbon and water fluxes of an intensively grazed dairy pasture in New Zealand [56], and to test effects of different climate and management practices on soil carbon stocks and milk production [57].…”

Section: Introductionmentioning

confidence: 99%

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Modeling Carbon and Water Fluxes of Managed Grasslands: Comparing Flux Variability and Net Carbon Budgets between Grazed and Mowed Systems

et al. 2019

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The CenW ecosystem model simulates carbon, water, and nitrogen cycles following ecophysiological processes and management practices on a daily basis. We tested and evaluated the model using five years eddy covariance measurements from two adjacent but differently managed grasslands in France. The data were used to independently parameterize CenW for the two grassland sites. Very good agreements, i.e., high model efficiencies and correlations, between observed and modeled fluxes were achieved. We showed that the CenW model captured day-to-day, seasonal, and interannual variability observed in measured CO2 and water fluxes. We also showed that following typical management practices (i.e., mowing and grazing), carbon gain was severely curtailed through a sharp and severe reduction in photosynthesizing biomass. We also identified large model/data discrepancies for carbon fluxes during grazing events caused by the noncapture by the eddy covariance system of large respiratory losses of C from dairy cows when they were present in the paddocks. The missing component of grazing animal respiration in the net carbon budget of the grazed grassland can be quantitatively important and can turn sites from being C sinks to being neutral or C sources. It means that extra care is needed in the processing of eddy covariance data from grazed pastures to correctly calculate their annual CO2 balances and carbon budgets.

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Section: Cenw 42 Overviewmentioning

confidence: 99%

Section: Cenw 42 Overviewmentioning

confidence: 99%

Section: Cenw 42 Overviewmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Modeling Carbon and Water Fluxes of Managed Grasslands: Comparing Flux Variability and Net Carbon Budgets between Grazed and Mowed Systems

et al. 2019

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“…that the cows show a temporally representative presence in the flux footprint (see Felber et al, 2015). Otherwise the annual F C-CO 2 ,tot would be affected by a systematic error as also noted by Kirschbaum et al (2015).…”

Section: Applicability Of the Necb Approachesmentioning

confidence: 84%

Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

et al. 2016

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Abstract. Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECB tot for system boundaries including the grazing cows and NECB past for system boundaries excluding the cows. CO 2 and CH 4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small near-neutral C budget: NECB tot −27 ± 62 and NECB past 23 ± 76 g C m −2 yr −1 . The considerable uncertainties, depending on the approach, were mainly due to errors in the CO 2 exchange or in the animal-related fluxes. The comparison of the NECB results with the annual exchange of other GHG revealed CH 4 emissions from the cows to be the major contributor in terms of CO 2 equivalents, but with much lower uncertainty compared to NECB. Although only 1 year of data limit the representativeness of the carbon budget results, they demonstrate the important contribution of the non-CO 2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

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Warming and Elevated CO2 Have Opposing Influences on Transpiration. Which is more Important?

Kirschbaum

McMillan

2018

Curr Forestry Rep

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Plant transpiration is a key component of the terrestrial water cycle, and it is important to understand whether rates are likely to increase or decrease in the future. Plant transpiration rates are affected by biophysical factors, such as air temperature, vapour pressure deficits and net radiation, and by plant factors, such as canopy leaf area and stomatal conductance. Under future climate change, global temperature increases, and associated increases in vapour pressure deficits, will act to increase canopy transpiration rates. Increasing atmospheric CO 2 concentrations, however, is likely to lead to some reduction in stomatal conductance, which will reduce canopy transpiration rates. The objective of the present paper was to quantitatively compare the importance of these opposing driving forces. First, we reviewed the existing literature and list a large range of observations of the extent of decreasing stomatal conductance with increasing CO 2 concentrations. We considered observations ranging from short-term laboratory-based experiments with plants grown under different CO 2 concentrations to studies of plants exposed to the naturally increasing atmospheric CO 2 concentrations. Using these empirical observations of plant responses, and a set of well-tested biophysical relationships, we then estimated the net effect of the opposing influences of warming and CO 2 concentration on transpiration rates. As specific cases studies, we explored expected changes in greater detail for six specific representative locations, covering the range from tropical to boreal forests. For most locations investigated, we calculated reductions in daily transpiration rates over the twenty-first century that became stronger under higher atmospheric CO 2 concentrations. It showed that the effect of CO 2 -induced reduction of stomatal conductance would have a stronger transpiration-depressing effect than the stimulatory effect of future warming. For currently cold regions, global warming would, however, lengthen the growing seasons so that annual sums of transpiration could increase in those regions despite reductions in daily transpiration rates over the summer months.

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Modelling carbon and water exchange of a grazed pasture in New Zealand constrained by eddy covariance measurements

Cited by 34 publications

References 62 publications

Modeling Carbon and Water Fluxes of Managed Grasslands: Comparing Flux Variability and Net Carbon Budgets between Grazed and Mowed Systems

Modeling Carbon and Water Fluxes of Managed Grasslands: Comparing Flux Variability and Net Carbon Budgets between Grazed and Mowed Systems

Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

Warming and Elevated CO2 Have Opposing Influences on Transpiration. Which is more Important?

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