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Where does the carbon go? A model-data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites.

De Kauwe MG, Medlyn BE, Zaehle S, Walker AP, Dietze MC, Wang YP, Luo Y, Jain AK, El-Masri B, Hickler T, Wårlind D, Weng E, Parton WJ, Thornton PE, Wang S, Prentice IC, Asao S, Smith B, McCarthy HR, Iversen CM, Hanson PJ, Warren JM, Oren R, Norby RJ - New Phytol. (2014)

Bottom Line: Observed eCO2 effects on allocation were dynamic.Allocation schemes based on constant fractions or resource limitations performed less well, with some models having unintended outcomes.Our recommendations to reduce uncertainty include: use of allocation schemes constrained by biomass fractions; careful testing of allocation schemes; and synthesis of allocation and turnover data in terms of model parameters.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.

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Response (elevated/ambient) of Net Primary Productivity (NPP), foliar biomass, whole-canopyspecific leaf area (SLA) and leaf area index (LAI) to CO2 enhancement at Duke (a) and OakRidge (b). The data shown are means over the years of the experimental measurements (Duke,1996–2005; Oak Ridge, 1998–2008), with error bars indicating interannual variability(± 1 SD). Foliage biomass and LAI data are means of the maximum value simulated/observedduring each year. SLA is calculated as whole-canopy LAI divided by foliage biomass. Observations areshown by the abbreviation ‘OBS’.
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fig04: Response (elevated/ambient) of Net Primary Productivity (NPP), foliar biomass, whole-canopyspecific leaf area (SLA) and leaf area index (LAI) to CO2 enhancement at Duke (a) and OakRidge (b). The data shown are means over the years of the experimental measurements (Duke,1996–2005; Oak Ridge, 1998–2008), with error bars indicating interannual variability(± 1 SD). Foliage biomass and LAI data are means of the maximum value simulated/observedduring each year. SLA is calculated as whole-canopy LAI divided by foliage biomass. Observations areshown by the abbreviation ‘OBS’.

Mentions: Differences in model predictions of ambient LAI are discussed in Walker et al. (2014); here we focus on the predicted eCO2 effecton LAI. This effect depends, first, on the NPP enhancement; second, on the change in allocation ofNPP to foliage; and, third, on any change in specific leaf area (SLA) with eCO2. Fig.4 shows the observed and modelled responses of NPP, foliarbiomass, SLA and LAI to eCO2. Most models predict that eCO2 leads to anincrease in NPP, but there is a reduction in foliage allocation, such that the increase in foliagebiomass is less than the increase in NPP. These predictions are generally consistent with theobservations. The exception to this rule is ISAM at Oak Ridge, where foliage allocation increased,as explained above, leading to a larger response of foliage biomass than of NPP.


Where does the carbon go? A model-data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites.

De Kauwe MG, Medlyn BE, Zaehle S, Walker AP, Dietze MC, Wang YP, Luo Y, Jain AK, El-Masri B, Hickler T, Wårlind D, Weng E, Parton WJ, Thornton PE, Wang S, Prentice IC, Asao S, Smith B, McCarthy HR, Iversen CM, Hanson PJ, Warren JM, Oren R, Norby RJ - New Phytol. (2014)

Response (elevated/ambient) of Net Primary Productivity (NPP), foliar biomass, whole-canopyspecific leaf area (SLA) and leaf area index (LAI) to CO2 enhancement at Duke (a) and OakRidge (b). The data shown are means over the years of the experimental measurements (Duke,1996–2005; Oak Ridge, 1998–2008), with error bars indicating interannual variability(± 1 SD). Foliage biomass and LAI data are means of the maximum value simulated/observedduring each year. SLA is calculated as whole-canopy LAI divided by foliage biomass. Observations areshown by the abbreviation ‘OBS’.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4260117&req=5

fig04: Response (elevated/ambient) of Net Primary Productivity (NPP), foliar biomass, whole-canopyspecific leaf area (SLA) and leaf area index (LAI) to CO2 enhancement at Duke (a) and OakRidge (b). The data shown are means over the years of the experimental measurements (Duke,1996–2005; Oak Ridge, 1998–2008), with error bars indicating interannual variability(± 1 SD). Foliage biomass and LAI data are means of the maximum value simulated/observedduring each year. SLA is calculated as whole-canopy LAI divided by foliage biomass. Observations areshown by the abbreviation ‘OBS’.
Mentions: Differences in model predictions of ambient LAI are discussed in Walker et al. (2014); here we focus on the predicted eCO2 effecton LAI. This effect depends, first, on the NPP enhancement; second, on the change in allocation ofNPP to foliage; and, third, on any change in specific leaf area (SLA) with eCO2. Fig.4 shows the observed and modelled responses of NPP, foliarbiomass, SLA and LAI to eCO2. Most models predict that eCO2 leads to anincrease in NPP, but there is a reduction in foliage allocation, such that the increase in foliagebiomass is less than the increase in NPP. These predictions are generally consistent with theobservations. The exception to this rule is ISAM at Oak Ridge, where foliage allocation increased,as explained above, leading to a larger response of foliage biomass than of NPP.

Bottom Line: Observed eCO2 effects on allocation were dynamic.Allocation schemes based on constant fractions or resource limitations performed less well, with some models having unintended outcomes.Our recommendations to reduce uncertainty include: use of allocation schemes constrained by biomass fractions; careful testing of allocation schemes; and synthesis of allocation and turnover data in terms of model parameters.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.

Show MeSH
Related in: MedlinePlus