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An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several...
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![Page 1: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/1.jpg)
An empirical model of stand GPP with LUE approach: analysis of eddy
covariance data at several contrasting sites
A. Mäkelä1, M. Pulkkinen1, P. Kolari1, F. Lagergren2, P. Berbigier3,
A. Lindroth2, D. Loustau3, E. Nikinmaa1, T.Vesala4 & P. Hari1
1 Department of Forest Ecology, University of Helsinki, Finland
2 Physical Geography and Ecosystems Analysis, Geobiosphere Center, Lund University, Sweden
3 INRA EPHYSE, France
4 Division of Atmospheric Sciences, Department of Physical Sciences, University of Helsinki, Finland
![Page 2: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/2.jpg)
Photosynthesis
SPP – a detailed process model using half-hourly weather data
Empirical model – daily weather data: APAR, T, VPD
Super Simple Model – annual GPP
Mäkelä et al. 2006, Agric. For. Meteor. 139:382-398
Mäkelä et al. in press, GCB
under development, MereGrowth
![Page 3: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/3.jpg)
Daily light use efficiency (LUE) model
where β = LUE at optimal conditions
Φk = PAR absorbed by canopy during day k
fi, k = modifying factors accounting for suboptimal conditions
in day k, fi,k [0, 1]
ek = random error in day k
Actual LUE in day k: β fL, k fS, k fD, k fW, k
,effffGPP kkW,kD,kS,kL,kk β
![Page 4: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/4.jpg)
Daily LUE model: modifiers
Light:
Temperature (state of acclimation):
1,S
minSf kSmax
k
S
111-kk1-kk TX,XT1
XX τ
0,XmaxS kk 0X
1
1f
kkL
γ
![Page 5: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/5.jpg)
Daily LUE model: modifiers
VPD:
Soil water (relative extractable water):
kDkD eDf κ
1
kW
W11Wf
υ
k
α
υkWα e1Wf kW
1,θθ
θθminWk
PWPFC
PWPk
![Page 6: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/6.jpg)
Estimation data
Sodankylä, Finland, 2001-2002• Scots pine, 50-80 yr, LAI 4.0
Hyytiälä, Finland, 2001-2003• Scots pine, 40 yr, LAI 7.0
Norunda, Sweden, 1995-2002• Scots pine & Norway spruce, 100 yr, LAI 11.7
Tharandt, Germany, 2001-2003• Norway spruce, 140 yr, LAI 22.8
Bray, France, 2001-2002• maritime pine, 30 yr, LAI 4.0
Sites
Variables
GPPk as a function of Tk (→ TERk) and eddy covariance NEEk : ecosystem GPPk
Φk as a constant fraction of above-canopy PARk : canopy Φk
![Page 7: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/7.jpg)
Parameter estimation
• For each year in each site → site-year-specific models
• Over all the years in each site → site-specific models
• Over all the years and sites → whole-data model
• Over all the years and sites with a separate LUE parameter β
for each site → varying-LUE model
Soil water modifier improved the fit significantly only in very few site-year combinations→ the following results are from the models with light, temperature and VPD modifiers
Results
![Page 8: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/8.jpg)
Parameter estimates are correlated within each site as well as across
sites: a "global" parameter set could perhaps be found
![Page 9: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/9.jpg)
Test with independent data
NOBS, Manitoba, Canada, 2000-2002
• black spruce, 160 yr, LAI 10.1
• moist, poor site with paludified areas in the vicinity
Metolius, Oregon, USA, 2002-2004
• ponderosa pine, 60 yr, LAI 8.0• dry, sandy site known for measurements of hydraulic limitation
Data
Test
Compare the measured daily GPP to the GPP predicted with
(i) the whole-data model
(ii) the varying-LUE model with a re-estimated LUE parameter β
![Page 10: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/10.jpg)
Discussion & Conclusions (but presentation continues)
A simple model with APAR, temperature and VPD as input could explain a major part of the day-to-day variation in the GPP of boreal and temperate coniferous canopies
The maximum LUE was found to vary between sites• influential factors omitted or mis-represented in the model: foliar nitrogen, ground floor vegetation, estimation of APAR
Some between-years variation in the GPP remained uncaptured in each site• year-to-year variation in LAI• estimation of GPP from eddy covariance NEE
Against expectation, soil water was not an important explanatory factor• soil water effect possibly embedded in the VPD effect
![Page 11: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/11.jpg)
Surprising finding by Annikki M.
Estimates of site-specific LUE parameters β:• for the European sites taken from the fitting of the variable-LUE model• for the Ameriflux sites estimated with linear regression
Measured GPP: eddy covariance GPP, mean of yearly totals
ΦTOT: fAPAR times growing season sum of above-canopy PAR, mean of yearly totals
Slope ≈ 0.45
![Page 12: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/12.jpg)
A closer look at GPPtot / ( Φtot) β̂
a);fff(WMb
β̂
efffΦ
β̂
β
β̂
)efffΦ β(
β̂
GPP
β̂
GPP41.0
DSL
kk
kk
kk
kk,Dk,Sk,Lk
kk
kkk,Dk,Sk,Lk
kk
kk
tot
tot
APAR-weighted mean of the daily product of the modifiers
≈ 1 ≈ 0
![Page 13: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/13.jpg)
Additional eddy flux data
At the moment 5 sites, 18 site-years
These additional data & original estimation and test data make altogether 42 site-years
Site Location Elevation
(m) Dominant species
Age (a)
Hdom
(m)
N (ha-1)
Years of data
Brasschaat, Belgium
51°18'N 4°31'E
16 Pinus sylvestris, Quercus robur
75 19 350 1997-1998, 2000-2002, 2004
Sorø, Denmark
55°29' N 11°36' E
40 Fagus sylvatica, Picea abies, Larix decidua
82 28 330 2005-2006
Zotino, Russia
60°45'N, 89°23'E
90 Pinus sylvestris 200 18 450 1999-2000
Wind River, Washington, USA
45°49'N, -121°57'W
371
Pseudotsuga menziesii, Tsuga heterophylla, Thuja plicata, Taxus brevifolia, Abies amabilis
500 52 430 1999-2004
Teshio, Hokkaido, Japan
45°03'N, 142°06'E
70
Quercus crispula, Betula ermanii, B. platyphylla, Abies sachalinensis, Picea jezoensis
165 24 2002
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We are still happy.
![Page 15: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/15.jpg)
Site-specific LUE parameters β vs. foliar nitrogen
![Page 16: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/16.jpg)
Potential usage of the ”super-simple” model: determine site-specific LUE from eddy covariance measurements and predict the future growing-season GPP with predicted growing season APAR
![Page 17: An empirical model of stand GPP with LUE approach: analysis of eddy covariance data at several contrasting sites A. Mäkelä 1, M. Pulkkinen 1, P. Kolari.](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e7b5503460f94b7d42b/html5/thumbnails/17.jpg)
Even more eddy flux data
Still 3 more sites to be included in the analysis (as well as 6 more years in Hyytiälä), 17 site-years
All the data will finally make altogether 59 site-years
Site Location Elevation
(m) Dominant species
Age (a)
Hdom
(m)
N (ha-1)
Years of data
Abisko River Delta, Sweden
68°21'N 18°47'E
376 Betula pubescens 2005
Renon, Italy
46°35'N 11°26'E
1730 Picea abies, Pinus cembra, Larix decidua
0-180 31 270 1999, 2001-2005
Tumbarumba, New South Wales, Australia
35°39'S 148°09'E
1200 Eucalyptus delegatensis, E. dalrymplean
2001-2005
Hyytiälä, Finland
61°51' N 24°18' E
170 Pinus sylvestris 42 14 1450 1997-2000, 2004-2005
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No changes in the degree of happiness.