Measuring and modelling environmental influences on photosynthetic gas exchange in Sphagnum and Pleurozium

Williams, T. G.; Flanagan, Lawrence B.

doi:10.1046/j.1365-3040.1998.00292.x

Cited by 130 publications

(158 citation statements)

References 22 publications

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“…Under non-irradiation-limited conditions, the photosynthesis of C3 plants and mosses is considered to correlate approximately linearly with the ambient CO 2 concentration at CO 2 concentrations between 300 ppm and 400 ppm. This has been shown by several previous studies (Morison and Gifford, 1983;Grulke et al, 1990;Stitt, 1991;Sage, 1994;Luo and Mooney, 1996;Williams and Flanagan, 1998;Griffin and Luo, 1999). Consequently, F P (t) can be modelled for periods with nonirradiation-limited photosynthesis of a canopy consisting of C3 plants and/or mosses, which is typical for tundra and peatlands, as:…”

Section: Development Of the Nonlinear Exponential Modelmentioning

confidence: 69%

CO2 flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

et al. 2007

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Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO 2 ) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO 2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO 2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO 2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO 2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO 2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO 2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO 2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evoCorrespondence to: L. Kutzbach (kutzbach@uni-greifswald.de) lution in the chamber headspace and estimation of the initial CO 2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO 2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO 2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO 2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO 2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO 2 balances than in the individual fluxes. To avoid serious bias of CO 2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

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Section: Development Of the Nonlinear Exponential Modelmentioning

confidence: 69%

CO2 flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

et al. 2007

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“…i assumed based on literature (Givnish, 2002;Reich et al, 1998) so that V max values are higher in evergreens than in deciduous and are in line with the values for trees. j V max of mosses is 14 in the summer and 6.5 in the remaining time (Williams and Flanagan, 1998).…”

Section: Heterotrophic Respirationmentioning

confidence: 98%

“…Williams and Flanagan, 1998;Robroek et al, 2009). In CLASS, evaporation at the soil surface is controlled by a soil evaporation efficiency coefficient β .…”

Section: Soil Layersmentioning

confidence: 99%

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Integrating peatlands into the coupled Canadian Land Surface Scheme (CLASS) v3.6 and the Canadian Terrestrial Ecosystem Model (CTEM) v2.0

Verseghy

Melton

2016

Geosci. Model Dev.

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Abstract. Peatlands, which contain large carbon stocks that must be accounted for in the global carbon budget, are poorly represented in many earth system models. We integrated peatlands into the coupled Canadian Land Surface Scheme (CLASS) and the Canadian Terrestrial Ecosystem Model (CTEM), which together simulate the fluxes of water, energy, and CO 2 at the land surface-atmosphere boundary in the family of Canadian Earth system models (CanESMs). New components and algorithms were added to represent the unique features of peatlands, such as their characteristic ground floor vegetation (mosses), the slow decomposition of carbon in the water-logged soils and the interaction between the water, energy, and carbon cycles. This paper presents the modifications introduced into the CLASS-CTEM modelling framework together with site-level evaluations of the model performance for simulated water, energy and carbon fluxes at eight different peatland sites. The simulated daily gross primary production (GPP) and ecosystem respiration are well correlated with observations, with values of the Pearson correlation coefficient higher than 0.8 and 0.75 respectively. The simulated mean annual net ecosystem production at the eight test sites is 87 g C m −2 yr −1 , which is 22 g C m −2 yr −1 higher than the observed annual mean. The general peatland model compares well with other site-level and regional-level models for peatlands, and is able to represent bogs and fens under a range of climatic and geographical conditions.

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“…The maximum rate of carboxylation (V cmax ) typically varies across peat sites (Rennermalm et al, 2005;Bubier et al, 2011) and further varies with leaf nitrogen, phosphorus content, and specific leaf area (Wright et al, 2004;Walker et al, 2014). For instance, V cmax for Sphagnum at the Old Black Spruce site (53.985 • N, 105.12 • W) in Canada was 5, 14, and 6 µmol m −2 s −1 during spring, summer, and autumn, respectively, while V cmax for Pleurozium was 7, 5, and 7 µmol m −2 s −1 during the three seasons (Williams and Flanagan, 1998). Bui (2013) conducted a fertilization experiment at the Mer Bleue Bog (Canada; 45.41 • N, 75.52 • W) on the dominant ericaceous shrub and reported that V cmax values ranged between 6 and 179 µmol m −2 s −1 , with significantly higher V cmax values after addition of nitrogen (6.4 g N m −2 yr −1 ) at 20 times the growing season ambient wet N deposition rate with or without phosphorus (P) and potassium (K).…”

Section: Modified Peat Plant Parametersmentioning

confidence: 99%

ORCHIDEE-PEAT (revision 4596), a model for northern peatland CO2, water, and energy fluxes on daily to annual scales

et al. 2018

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Abstract. Peatlands store substantial amounts of carbon and are vulnerable to climate change. We present a modified version of the Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface model for simulating the hydrology, surface energy, and CO 2 fluxes of peatlands on daily to annual timescales. The model includes a separate soil tile in each 0.5 • grid cell, defined from a global peatland map and identified with peat-specific soil hydraulic properties. Runoff from non-peat vegetation within a grid cell containing a fraction of peat is routed to this peat soil tile, which maintains shallow water tables. The water table position separates oxic from anoxic decomposition. The model was evaluated against eddy-covariance (EC) observations from 30 northern peatland sites, with the maximum rate of carboxylation (V cmax ) being optimized at each site. Regarding short-term day-to-day variations, the model performance was good for gross primary production (GPP) (r 2 = 0.76; NashSutcliffe modeling efficiency, MEF = 0.76) and ecosystem respiration (ER, r 2 = 0.78, MEF = 0.75), with lesser accuracy for latent heat fluxes (LE, r 2 = 0.42, MEF = 0.14) and and net ecosystem CO 2 exchange (NEE, r 2 = 0.38, MEF = 0.26). Seasonal variations in GPP, ER, NEE, and energy fluxes on monthly scales showed moderate to high r 2 values (0.57-0.86). For spatial across-site gradients of annual mean GPP, ER, NEE, and LE, r 2 values of 0.93, 0.89, 0.27, and 0.71 were achieved, respectively. Water table (WT) variation was not well predicted (r 2 < 0.1), likely due to the uncertain water input to the peat from surrounding areas. However, the poor performance of WT simulation did not greatly affect predictions of ER and NEE. We found a significant relationship between optimized V cmax and latitude (temperature), which better reflects the spatial gradients of annual NEE than using an average V cmax value.

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Measuring and modelling environmental influences on photosynthetic gas exchange in Sphagnum and Pleurozium

Abstract: A mechanistic model has been used to examine the environmental regulation of photosynthetic gas exchange in moss. The effects of water content on conductance to CO 2 and on photosynthetic capacity during desiccation were calculated from the carbon isotope discrimination data of

Cited by 130 publications

References 22 publications

CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

Integrating peatlands into the coupled Canadian Land Surface Scheme (CLASS) v3.6 and the Canadian Terrestrial Ecosystem Model (CTEM) v2.0

ORCHIDEE-PEAT (revision 4596), a model for northern peatland CO<sub>2</sub>, water, and energy fluxes on daily to annual scales

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Measuring and modelling environmental influences on photosynthetic gas exchange in Sphagnum and Pleurozium

Abstract: A mechanistic model has been used to examine the environmental regulation of photosynthetic gas exchange in moss. The effects of water content on conductance to CO 2 and on photosynthetic capacity during desiccation were calculated from the carbon isotope discrimination data of

Cited by 130 publications

References 22 publications

CO&lt;sub&gt;2&lt;/sub&gt; flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

CO&lt;sub&gt;2&lt;/sub&gt; flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

Integrating peatlands into the coupled Canadian Land Surface Scheme (CLASS) v3.6 and the Canadian Terrestrial Ecosystem Model (CTEM) v2.0

ORCHIDEE-PEAT (revision 4596), a model for northern peatland CO&lt;sub&gt;2&lt;/sub&gt;, water, and energy fluxes on daily to annual scales

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Product

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CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

ORCHIDEE-PEAT (revision 4596), a model for northern peatland CO<sub>2</sub>, water, and energy fluxes on daily to annual scales