On the role of advec/on for the net ecosystem
carbon dioxide exchange of a subalpine grassland
Georg Wohlfahrt1,
Marta Galvagno2, Edoardo Cremonese2, Umberto Morra di Cella2
1 Ins&tut für Ökologie, Universität Innsbruck, Austria
2 Agenzia Regionale per la Protezione dell’Ambiente del Valle di Aosta, Italy
Background
2
0 0 0
2
0 0 0
' ' ' ' ' '
2
0 0 0
1
1
1
L L h d
L L h
d d d
L L h
d d d
F c dxdydz
L t
uc vc wc dxdydz
L x y z
c u c v c w
dxdydz
L x y z
δχ δ
δ χ δ χ δ χ
δ δ δ
δ χ δ χ δ χ
δ δ δ
= +
⎡ ⎤
+ + +
⎢ ⎥
⎣ ⎦
⎡ ⎤
+ +
⎢ ⎥
⎢ ⎥
⎣ ⎦
∫∫∫
∫∫∫
∫∫∫
' ' 0
h
d d
F c dz c w t
δχ χ
= ∫ δ +
Background
' ' 0
h
d d
F c dz c w t
δχ χ
= ∫ δ +
Complex terrain
me
1000km
draFing his 1995 PCE papers Ray in Canberra 1994
Mt. Arapiles
Complex terrain
2012 Innsbruck
hDp://youtu.be/UshxZSOoeCg
Complex terrain
“… errors associated with measurement uncertain&es outweigh the advantages of the micrometeorological mass balance approach
…” (Leuning et al., 2008)
Study site
• Study site: Torgnon
• Subalpine grassland (2160 m)
• EC site on li[le plateau, bounded by steep slopes
• Complexity at all spa&al scales
• Short canopy (20 cm)
Methods
Study site
Study site
Methods
Methods
Results
Results
Results
Conclusions
• The sum of the ver&cal covariance term and the storage term considerably underes&mated nigh]me ecosystem respira&on as measured by the automated ecosystem chambers.
• Advec&on measurements indicated that both horizontal and (less so) ver&cal advec&on were important terms of the mass balance during nigh]me.
• The NEE calculated by taking advec&on into account closely resembled nigh]me ecosystem respira&on as measured with the automated ecosystem chambers.
• During day&me, advec&on appeared to make a negligible contribu&on to NEE.
• Large spa&al variability in the ver&cal eddy covariance term within short distances.
