Improving GPP, NPP, and NEE predictions from space

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Improving GPP, NPP, and NEE predictions from space

• Richard Waring1
• Nicholas Coops2
• Joe Landsberg3
• 1 Oregon State University
• 2 University of British Columbia
• 3 Mt Wilson, NSW 2786, Australia

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Eucalyptus plantation GPP 6,000 g C m-2 yr-1
Brazilian rainforest GPP 3,000 g C m-2 yr-1
Photo Courtesy of Auro Almeida
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Brazilian plantation LAI decreases with age as
trees approach 40 m in height at 7 years when
harvested. Drought reduces LAI more when stand is
young than older
Drought
Drought
Auro Almeida, CSIRO Tasmania, unpublished
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In the Atlantic Coastal Region of
Brazil, native rainforests and eucalyptus
plantations use similar amounts of water although
LAI differs by gt 2 fold. Reason eucalypts are
fertilized have twice the photosynthetic
capacity and twice the max. canopy
conductance of the rainforest.
Auro Almeida, CSIRO Tasmania, unpublished
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Objective to provide ecological insights to
improve predictions of GPP, NPP, and NEE from
space

1. GPP set limits and identify constraints
2. NPP allocation above and below ground
3. NEE correlation with GPP

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Ecosystem Model Structure
Waring, Coops, Landsberg 2009 For. Ecol Mgmt
(in press)
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Leaf chlorophyll conc. linearly related to
maximum photosynthetic capacity (link to soil
fertility)
Zhang et al. 2009. Remote Sen. Env. 113 880-888.
Waring et al. 1995. Plant Cell Env. 18
1201-1218.
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Leaf conductance (g) and photosynthetic capacity
(A) decrease with (relative) tree height
hydraulic conductivity (KL)
Ambrose et al. 2009. Plant, Cell Env. 32
743-757. Hubbard et al. 2001. Plant, Cell Env.
24 113-121.
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Stomatal response to vpd varies by an order of
magnitude among species in boreal forests
Dang et al. 1997. Tree Physiology 17 521-535.
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VPD response is a function of maximum canopy
conductance

• Stomatal sensitivity to vpd is a negative log
  function (slope 0.6) to maximum conductance at ?
  1 kPa (r2 0.75).
• Oren et al. 1999. Plant, Cell
  Env.221515-1535.

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As the soil water deficit increases beyond a
threshold, water loss through transpiration is
progressively reduced below its potential as
stomata close
Eucalyptus maculata
Source Landsberg Gower 1997. Fig. 4.5.
Application of Physiological Ecology to Forest
Management. Academic Press, San Diego, CA
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Root depth determines access to water
Eucalyptus marginata
28 m
depth that roots penetrate
Photo courtesy of Keith Smettem, University of
Western Australia
Photo courtesy of E.D. Schulze
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To evaluate soil water limitations, need to
assess changes in canopy properties (LAI, fPAR,
PRI, wetness)
Canadell et al. 1996. Oecologia 108583-595
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Photosynthetic Reflectance Index(Gamon et al.
1992. Rem. Sen. Env. 4135-44)
8 species in New Zealand
Olive trees
Suarez et al. 2009. Rem.Sen. Env. 113730-744.
Trotter et al. 2002. Int. J. Rem. Sen.23
1207-1212.
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Douglas-fir (sunlite) Campbell River, B.C.
Hall et al. 2008. Remote Sensing of Env. 112
3201-3211
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Partitioning of forest NPP below ground ranges
from 20 to 60 (Waring et al. (1998). When GPP ?
2500 g C m-2 yr-1 (respiration NPPb) minimum
N 38
young ponderosa pine
tropical savanna
black spruce jack pine old ponderosa pine

• Litton et al.

plantations
aspen
Litton et al. 2007. Global Change Biology 13
2080-2109 Chen et al. 2003. Oecologia 137
405-416 Stape et al. 2008. For. Ecol. Mgmt.
255 920-930. Waring et al. 1998. Tree Physiol.
18129-134.
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NEE varies seasonally by type of vegetation, as
does GPP
After Baldocchi 2009 Aust. J. Bot. (in press)
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Predicting Ecosystem Respiration or NEE
(GPP-Reco) as a function of eddy-flux
measured GPP
?0.94
r2 0.9 ?0.77
After Baldocchi 2009 Aust. J. Bot. (in press)
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To improve predictions of GPP, NPP, and NEE from
space

• Chlorophyll light absorbance is better than
  nitrogen content to estimate max. conductance and
  photosynthetic capacity.
• Max. conductance and photosynthetic capacity are
  reduced as trees approach site species-specific
  maximum height.
• PRI is a good check on modeled constraints on GPP
• GPP is more important to estimate accurately than
  NPP, although NPPA would be helpful to validate
  model predictions of growth allocation.
• Allocation of NPP ( respiration) increases
  below-ground if water and nutrients are not
  available, generally not the case if GPP ? 2500 g
  C m-2 yr-1.
• Ecosystem respiration is 75 of GPP in
  undisturbed systems, 95 in
• disturbed systems. Be able to distinguish
  disturbed systems recovery.

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• Email
• Richard.Waring_at_oregonstate.edu
• Nicholas Coops nicholas.coops_at_ubc.ca
• Joe Landsberg jlandsberg_at_netspeed.com.au
• Waring, Coops, Landsberg. 2009.
• Improving predictions of forest growth
• using the 3-PGS model with observations
• made by remote sensing. For. Ecol. Mgmt.
  
• (in press). (RHW Pub. No. 108).
• www.fsl.orst.edu/waring