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Does canopy mean nitrogen concentration explain variation in canopy light use efficiency across 14 contrasting forest sites?

Peltoniemi, Mikko; Pulkkinen, Minna; Kolari, Pasi; Duursma, Remko A.; Montagnani, Leonardo; Wharton, Sonia; Lagergren, Fredrik LU ; Takagi, Kentaro; Verbeeck, Hans and Christensen, Torben LU , et al. (2012) In Tree Physiology 32(2). p.200-218
Abstract
The maximum light use efficiency (LUE = gross primary production (GPP)/absorbed photosynthetic photon flux density (aPPFD)) of plant canopies has been reported to vary spatially and some of this variation has previously been attributed to plant species differences. The canopy nitrogen concentration [N] can potentially explain some of this spatial variation. However, the current paradigm of the N-effect on photosynthesis is largely based on the relationship between photosynthetic capacity (A(max)) and [N], i.e., the effects of [N] on photosynthesis rates appear under high PPFD. A maximum LUE-[N] relationship, if it existed, would influence photosynthesis in the whole range of PPFD. We estimated maximum LUE for 14 eddy-covariance forest... (More)
The maximum light use efficiency (LUE = gross primary production (GPP)/absorbed photosynthetic photon flux density (aPPFD)) of plant canopies has been reported to vary spatially and some of this variation has previously been attributed to plant species differences. The canopy nitrogen concentration [N] can potentially explain some of this spatial variation. However, the current paradigm of the N-effect on photosynthesis is largely based on the relationship between photosynthetic capacity (A(max)) and [N], i.e., the effects of [N] on photosynthesis rates appear under high PPFD. A maximum LUE-[N] relationship, if it existed, would influence photosynthesis in the whole range of PPFD. We estimated maximum LUE for 14 eddy-covariance forest sites, examined its [N] dependency and investigated how the [N]-maximum LUE dependency could be incorporated into a GPP model. In the model, maximum LUE corresponds to LUE under optimal environmental conditions before light saturation takes place (the slope of GPP vs. PPFD under low PPFD). Maximum LUE was higher in deciduous/mixed than in coniferous sites, and correlated significantly with canopy mean [N]. Correlations between maximum LUE and canopy [N] existed regardless of daily PPFD, although we expected the correlation to disappear under low PPFD when LUE was also highest. Despite these correlations, including [N] in the model of GPP only marginally decreased the root mean squared error. Our results suggest that maximum LUE correlates linearly with canopy [N], but that a larger body of data is required before we can include this relationship into a GPP model. Gross primary production will therefore positively correlate with [N] already at low PPFD, and not only at high PPFD as is suggested by the prevailing paradigm of leaf-level A(max)-[N] relationships. This finding has consequences for modelling GPP driven by temporal changes or spatial variation in canopy [N]. (Less)
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Contribution to journal
publication status
published
subject
keywords
canopy nitrogen concentration, eddy covariance, gross primary, production, light use efficiency, quantum yield, vegetation productivity
in
Tree Physiology
volume
32
issue
2
pages
200 - 218
publisher
Oxford University Press
external identifiers
  • wos:000300988800010
  • scopus:84860614677
ISSN
1758-4469
DOI
10.1093/treephys/tpr140
project
BECC
MERGE
language
English
LU publication?
yes
id
00020412-ef57-4df2-992a-eab6edd1713a (old id 2384498)
date added to LUP
2012-03-30 14:23:23
date last changed
2017-01-01 06:04:46
@article{00020412-ef57-4df2-992a-eab6edd1713a,
  abstract     = {The maximum light use efficiency (LUE = gross primary production (GPP)/absorbed photosynthetic photon flux density (aPPFD)) of plant canopies has been reported to vary spatially and some of this variation has previously been attributed to plant species differences. The canopy nitrogen concentration [N] can potentially explain some of this spatial variation. However, the current paradigm of the N-effect on photosynthesis is largely based on the relationship between photosynthetic capacity (A(max)) and [N], i.e., the effects of [N] on photosynthesis rates appear under high PPFD. A maximum LUE-[N] relationship, if it existed, would influence photosynthesis in the whole range of PPFD. We estimated maximum LUE for 14 eddy-covariance forest sites, examined its [N] dependency and investigated how the [N]-maximum LUE dependency could be incorporated into a GPP model. In the model, maximum LUE corresponds to LUE under optimal environmental conditions before light saturation takes place (the slope of GPP vs. PPFD under low PPFD). Maximum LUE was higher in deciduous/mixed than in coniferous sites, and correlated significantly with canopy mean [N]. Correlations between maximum LUE and canopy [N] existed regardless of daily PPFD, although we expected the correlation to disappear under low PPFD when LUE was also highest. Despite these correlations, including [N] in the model of GPP only marginally decreased the root mean squared error. Our results suggest that maximum LUE correlates linearly with canopy [N], but that a larger body of data is required before we can include this relationship into a GPP model. Gross primary production will therefore positively correlate with [N] already at low PPFD, and not only at high PPFD as is suggested by the prevailing paradigm of leaf-level A(max)-[N] relationships. This finding has consequences for modelling GPP driven by temporal changes or spatial variation in canopy [N].},
  author       = {Peltoniemi, Mikko and Pulkkinen, Minna and Kolari, Pasi and Duursma, Remko A. and Montagnani, Leonardo and Wharton, Sonia and Lagergren, Fredrik and Takagi, Kentaro and Verbeeck, Hans and Christensen, Torben and Vesala, Timo and Falk, Matthias and Loustau, Denis and Makela, Annikki},
  issn         = {1758-4469},
  keyword      = {canopy nitrogen concentration,eddy covariance,gross primary,production,light use efficiency,quantum yield,vegetation productivity},
  language     = {eng},
  number       = {2},
  pages        = {200--218},
  publisher    = {Oxford University Press},
  series       = {Tree Physiology},
  title        = {Does canopy mean nitrogen concentration explain variation in canopy light use efficiency across 14 contrasting forest sites?},
  url          = {http://dx.doi.org/10.1093/treephys/tpr140},
  volume       = {32},
  year         = {2012},
}