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Which are the most important parameters for modelling carbon assimilation in boreal Norway spruce under elevated [CO2] and temperature conditions?

Hall, Marianne LU ; Medlyn, Belinda E; Abramowitz, Gab; Franklin, Oskar; Räntfors, Mats; Linder, Sune and Wallin, Göran (2013) In Tree Physiology 33(11). p.1156-1176
Abstract
Photosynthesis is highly responsive to environmental and physiological variables, including phenology, foliage nitrogen (N) content, atmospheric CO2 concentration ([CO2]), irradiation (Q), air temperature (T) and vapour pressure deficit (D). Each of these responses is likely to be modified by long-term changes in climatic conditions such as rising air temperature and [CO2]. When modelling photosynthesis under climatic changes, which parameters are then most important to calibrate for future conditions? To assess this, we used measurements of shoot carbon assimilation rates and microclimate conditions collected at Flakaliden, northern Sweden. Twelve 40-year-old Norway spruce trees were enclosed in whole-tree chambers and exposed to elevated... (More)
Photosynthesis is highly responsive to environmental and physiological variables, including phenology, foliage nitrogen (N) content, atmospheric CO2 concentration ([CO2]), irradiation (Q), air temperature (T) and vapour pressure deficit (D). Each of these responses is likely to be modified by long-term changes in climatic conditions such as rising air temperature and [CO2]. When modelling photosynthesis under climatic changes, which parameters are then most important to calibrate for future conditions? To assess this, we used measurements of shoot carbon assimilation rates and microclimate conditions collected at Flakaliden, northern Sweden. Twelve 40-year-old Norway spruce trees were enclosed in whole-tree chambers and exposed to elevated [CO2] and elevated air temperature, separately and in combination. The treatments imposed were elevated temperature, +2.8 °C in July/August and +5.6 °C in December above ambient, and [CO2] (ambient CO2 ∼370 μ mol mol(-1), elevated CO2 ∼700 μ mol mol(-1)). The relative importance of parameterization of Q, T and D responses for effects on the photosynthetic rate, expressed on a projected needle area, and the annual shoot carbon uptake was quantified using an empirical shoot photosynthesis model, which was developed and fitted to the measurements. The functional form of the response curves was established using an artificial neural network. The [CO2] treatment increased annual shoot carbon (C) uptake by 50%. Most important was effects on the light response curve, with a 67% increase in light-saturated photosynthetic rate, and a 52% increase in the initial slope of the light response curve. An interactive effect of light saturated photosynthetic rate was found with foliage N status, but no interactive effect for high temperature and high CO2. The air temperature treatment increased the annual shoot C uptake by 44%. The most important parameter was the seasonality, with an elongation of the growing season by almost 4 weeks. The temperature response curve was almost flat over much of the temperature range. A shift in temperature optimum had thus an insignificant effect on modelled annual shoot C uptake. The combined temperature and [CO2] treatment resulted in a 74% increase in annual shoot C uptake compared with ambient conditions, with no clear interactive effects on parameter values. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Tree Physiology
volume
33
issue
11
pages
1156 - 1176
publisher
Oxford University Press
external identifiers
  • wos:000328374500004
  • pmid:23525155
  • scopus:84890256421
ISSN
1758-4469
DOI
10.1093/treephys/tpt014
project
MERGE
BECC
language
English
LU publication?
yes
id
66d4e9a8-64d7-4c82-a73e-a370fd0ff1ca (old id 3627729)
date added to LUP
2013-06-27 20:33:48
date last changed
2019-08-07 01:13:53
@article{66d4e9a8-64d7-4c82-a73e-a370fd0ff1ca,
  abstract     = {Photosynthesis is highly responsive to environmental and physiological variables, including phenology, foliage nitrogen (N) content, atmospheric CO2 concentration ([CO2]), irradiation (Q), air temperature (T) and vapour pressure deficit (D). Each of these responses is likely to be modified by long-term changes in climatic conditions such as rising air temperature and [CO2]. When modelling photosynthesis under climatic changes, which parameters are then most important to calibrate for future conditions? To assess this, we used measurements of shoot carbon assimilation rates and microclimate conditions collected at Flakaliden, northern Sweden. Twelve 40-year-old Norway spruce trees were enclosed in whole-tree chambers and exposed to elevated [CO2] and elevated air temperature, separately and in combination. The treatments imposed were elevated temperature, +2.8 °C in July/August and +5.6 °C in December above ambient, and [CO2] (ambient CO2 ∼370 μ mol mol(-1), elevated CO2 ∼700 μ mol mol(-1)). The relative importance of parameterization of Q, T and D responses for effects on the photosynthetic rate, expressed on a projected needle area, and the annual shoot carbon uptake was quantified using an empirical shoot photosynthesis model, which was developed and fitted to the measurements. The functional form of the response curves was established using an artificial neural network. The [CO2] treatment increased annual shoot carbon (C) uptake by 50%. Most important was effects on the light response curve, with a 67% increase in light-saturated photosynthetic rate, and a 52% increase in the initial slope of the light response curve. An interactive effect of light saturated photosynthetic rate was found with foliage N status, but no interactive effect for high temperature and high CO2. The air temperature treatment increased the annual shoot C uptake by 44%. The most important parameter was the seasonality, with an elongation of the growing season by almost 4 weeks. The temperature response curve was almost flat over much of the temperature range. A shift in temperature optimum had thus an insignificant effect on modelled annual shoot C uptake. The combined temperature and [CO2] treatment resulted in a 74% increase in annual shoot C uptake compared with ambient conditions, with no clear interactive effects on parameter values.},
  author       = {Hall, Marianne and Medlyn, Belinda E and Abramowitz, Gab and Franklin, Oskar and Räntfors, Mats and Linder, Sune and Wallin, Göran},
  issn         = {1758-4469},
  language     = {eng},
  number       = {11},
  pages        = {1156--1176},
  publisher    = {Oxford University Press},
  series       = {Tree Physiology},
  title        = {Which are the most important parameters for modelling carbon assimilation in boreal Norway spruce under elevated [CO2] and temperature conditions?},
  url          = {http://dx.doi.org/10.1093/treephys/tpt014},
  volume       = {33},
  year         = {2013},
}