treenet–linking net ecosystem productivity of forests to wood growth and tree water relations with...

Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Roman Zweifel 1

TreeNet – Linking net ecosystem productivity of forests to wood growth and tree water relations with dendrometer-based data

Roman Zweifel (WSL), Matthias Haeni (WSL), Susanne Burri (ETHZ), ReinhardBischoff, (DecentLab), Nina Buchmann (ETHZ), Werner Eugster (ETHZ)

with the financial support of the Swiss Federal Office for the Environment FOEN

ICOS Science Conference, 27-29 September 2016, Helsinki, Finland

TreeNet - The biological drought and growth indicator network

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Monitoring- and research network based on continuously measured and auto-matically stored stem radius change data in a central data base in the cloud.

-> TreeNet Switzerland o near real-time datao 10 min resolutiono about 250 treeso at 30 sites in CHo main tree species

www.treenet.info

-> Financially support by o Federal Office of Environment FOEN o ICOS

o WSLo ETHZo SNFo COSTo Mercator Stiftung

-> Project partner o Institute for Applied Plant Biology IAP

-> Tech partner o DecentLab GmbH

Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Roman Zweifel

TreeNet – The smart technology behind it -> www.treenet.info

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-> Measurement in the field-> Data acquisition-> Data transfer from the field into a data base-> Data/infrastructure monitoring-> Data storage, cleaning, processing and online display-> Data download (user specific)-> Data analysing tools

www.decentlab.com


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Combining eddy covariance-based net ecosystem productivity (NEP) ...

... to dendrometer-based stem radiusincrements (SRI)


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Eddy CovarianceNet ecosystem productivity (NEP)

Point dendrometersWood biomassaccumulationandstem shrinkage due to tree water relations


Linking stem radius fluctuations (SRI) to netecosystem productivity NEP (eddy covariance)

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Seehornwald Davos, CH (Norway spruce forest, 1650 m asl)

adapted from Zweifel et al. (2010), New Phytologist


y = 0.2571x - 107.93 R² = 0.78

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NEP

[g

C m

-2 y

r-1]

GRO [µm yr-1]

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Linking stem radius fluctuations (SRI) to netecosystem productivity NEP (eddy covariance)

High correlation between annualvalues of SRI and NEP(Davos, Norway Spruce)

Potential of TreeNet to extrapolateEddy data from two measurementpoints over entire CHZweifel et al. (2010), New Phytologist

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1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

NEP

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C-S

ou

rce

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ink

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ydra

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SRI

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Linking stem radius fluctuations (SRI) to net ecosystemproductivity NEP (eddy covariance)


PhD

-thes

isM

atth

ias

Hae

ni, E

THZ

2014

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PhD-thesis Matthias Haeni, ETHZ 2014


Estimating net ecosystem productivity (NEP) fromdendrometer measurements (SRI)

-> Very close relationship for all sites-> Site-specific slope

Estimating net ecosystem productivity (NEP) fromdendrometer measurements (SRI)

-> Site-specific slope determinable from SRI data-> time to grow (tg)

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PhD-thesis Matthias Haeni, ETHZ 2014NEPc (i) = tg (SRIc) * SRIc (i)


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The generally close relationship between SRI and NEP ...

... leaves us with the question: why are some adult trees producing a (dendrometer) signal that explains the net gas exchange of the entire forest ecosystem?


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Water flow Water storage (reversible)

Growth(irreversible)

GRO

Analysing stem radius fluctuations (SRI) data


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Bark/PhloemXylem

CambiumSa

tura

ted

tree

stem

Dry

tree

stem

Point dendrometersmeasure:

• water related shrinkage andexpansion of stem (reversible)

• stem growth: cell division andelongation leading to new(irreversible) biomass in thewood and new (temporary) biomass in the bark


Zweifel et al. 2000, Trees

TWD is the missing water of a tree to fully saturate its tissues

Growth = cell division and cell expansion

Zweifel 2015 PCE,Zweifel et al. 2016 New Phytologist

14Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Roman Zweifel

Stem radius changes (SRI) = Growth (GRO) - Tree water deficit (TWD)

Tree rings alone explain less of NEP then SRI

(Rocha et al., 2006)

The secret lays in the bark (growth and reversible shrinking processes)

15Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Roman Zweifel

Stem radius changes (SRI) = Growth (GRO) - Tree water deficit (TWD)

Current year conditions are not fully explaining SRI and NEP

Carry-over effects (time lags) play an important role in determining SRI and NEP

Zielis et al., 2014Gough et al., 2008

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Timing of growth


Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Roman Zweifel 17

Take home message ...

... consistently close link between stem radius increments (SRI) and net ecosystem productivity (NEP)

... SRI consists of growth and tree water relations

... both seems to be important for the close relationship between SRI and NEP -> the secret lays in the bark

... carry-over effects determine SRI and NEP -> indirect coupling

... underlying mechanisms not fully understood yet

... great chance to up-scale results from carbon flux sites to entire landscapes with the help of SRI

... visit www.treenet.info

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Thank you forthe attention


Do you offer data sets combining NEP and SRI?

19Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Roman Zweifel Seehornwald Davos (CH-DAV)