Belowground carbon demand causes early culmination of ...€¦ · spruce exposed to drought stress...
Transcript of Belowground carbon demand causes early culmination of ...€¦ · spruce exposed to drought stress...
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Belowground carbon demand causes early culmination of radial stem growth in Norway spruce exposed to drought stress in spring
Walter OberhuberAndreas Gruber
Gina Rainer-LethausAndrea WinklerGerhard Wieser
General Assembly9-13 Apr 2018 Vienna, Austria
Austrian Science Fund
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Dry inner alpine valley
Background
Oetz (775 m)7.3 °C 714 mm
J F M A M J J A S O N D
Prec
ipita
tion
(mm
)
Tem
pera
ture
(°C
)
20
10
0
20
0
40
80
60
100
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Pinus sylvestris, Picea abies, Larix decidua
5 - 10 cm15 - 20 cm
750 m a.s.l.
Background
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Climate-growth relationships
Schuster and Oberhuber (2013) Trees
A M JC
oeffi
cien
t
Precipitation in spring favours radial stem growth
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Early culmination of radial stem growth
Pinus sylvestrisLarix decidua
Picea abies
7.3 oC 714 mm
J F M A M J J A S O N D
Prec
ipita
tion
(mm
)
Tem
pera
ture
(oC
)
20
10
0
20
0
40
80
60
100
Oberhuber et al. (2014) Eur J For Res
Maximum radial stem growth
Intra-annual dynamics of radial stem growth
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Carbon allocation belowground is prioritized over radial stem growthunder drought
90 Norway spruce treesc. 1.5 m height and 6 yr old
watered drought-stressed 18.1 ± 3.9 %
9.0 ± 1.9 %
Hypothesis
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Upper zone (UZ)
Middle zone (MZ)
Lower zone (LZ)
Cambium marking
NSC-content: determined after the growing seasonin UZ, MZ and LZ and coarse roots
Double girdling
cambial zonephloem
bark
P
woundingin mid-May
2014
2015
growth ring boundary
growth after wounding
growth beforewounding
Experimental design
Growth-regulating factors (auxin, cytokinin) ?
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watered trees
drought-stressed trees
growth onset
end
end
Girdling at different phenological stages
double girdlingdates
GD 177 doy
GD 2138 doy
GD 3190 doy
Oberhuber et al. (2017) Env Exp Bot
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Upper zone
2014
2015girdling and ‚pinning‘ in May
cambial zonephloem
growth after girdling
growthbeforegirdling
Girdling during the growing season - watered tree
growth ring boundary
Middle and lower zone
2014
2015
cambial zonephloembark
growthbeforegirdling
NO growthafter girdling
Upper zone
Middle zone
Lower zone
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Winkler and Oberhuber (2017) Tree Physiol
controlgirdling in July
Girdling after the end of the growing season - drought stressed tree
latewood
earlywood
cambialreactivationafter girdling
traumaticresin ducts
cambial zonephloem
bark
cambial zonephloem
bark
drought
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Radial stem growth in response to girdling
drought stressed
watered
girdling datesMarch May July
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minirhizotron technique
Fine root mass in response to girdling
Rainer-Lethaus and Oberhuber (2018) Front Plant Sci
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control
GD doy 77
GD doy 138
GD doy 190
Longitudinal root growth after girdling - drought stressed treeGrowth onset
Rainer-Lethaus and Oberhuber (2018) Front Plant Sci
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Rainer-Lethaus and Oberhuber (2018) Front Plant Sci
Radial root growth in response to girdling
drought stressed
watered
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Carbon status in girdled trees - stem
Oberhuber et al. (2017) Env Exp Bot
drought stressedwatered
control
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Carbon status in girdled trees – coarse root
Oberhuber et al. (2017) Env Exp Bot
drought stressedwatered
control
Decrease in starch content:radial growthmaintenance respirationresin production
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Summary
• radial growth increase was more intense under drought
• reactivation of cambium activity in drought-stressed trees
In response to phloem girdling:
• altered C availability stimulated radial growth
• decrease in starch content (except shoot)
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Conclusion7.3 oC 714 mm
J F M A M J J A S O N D
Prec
ipita
tion
(mm
)
Tem
pera
ture
(oC
)
20
10
0
20
0
40
80
60
100
Thank you for your attention Austrian Science Fund
Belowground carbon demand causes early culmination of radial stem growth under drought
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Shoot growth
Oberhuber et al. (2017) Env Exp Bot