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great importance; they provide the opportunity to study greenhouse gas dynamics
and its (feedback) mechanics in detail. In the following the most important methods
for quantifying biosphere-atmosphere gas
fluxes will be described.
Micrometeorological techniques, such as the Eddy Covariance (EC) technique,
use the covariance between the vertical air velocity and concentration of an entity to
calculate the
fl
flux of this entity. For EC-measurements, fast (10 Hz) wind and
concentration measurements are required. Fast analyzers for CO
2
and H
2
O are
worldwide available and recent technology developments resulted in fast analyzers
for other gases,
fl
such as CH
4
and N
2
O. However, due
to usual
low
CH
4
concentrations and -exchange, high quality EC-measurements
for these gases are dif
and N
2
O
cult (McDermitt et al.
2011
; Zona et al.
2013
). In contrast,
accumulation techniques are suitable for measurement of minor
fl
fluxes (Grif
th and
Galle
2000
). An example is the
flux gradient method, which was used in this study.
Flux chamber techniques are based on the principle of sealing an area by placing
fl
a
on top. Fluxes are derived from the change in gas concentration in the
chamber headspace. Flux chamber designs vary and have been evaluated exten-
sively (Pumpanen et al.
2004
). In our study, a dynamic
'
chamber
'
flux chamber system is
used. In Table
1
, the advantages (underlined) and disadvantages of micrometeo-
rological and
fl
flux chamber methods are summarized.
Both methods can complement each other; therefore systems combining dif-
ferent flux measurement methods are recommended (Myklebust et al.
2008
; Sturm
et al.
2012
). In this paper, a setup is described in which a Fourier Transform
Infrared Spectrometer (FTIR) is connected to two
fl
flux measurement techniques
which enables the measurement of different (greenhouse) gas emissions simulta-
neously, frequently and continuously.
fl
Table 1 Advantages (underlined) and disadvantages of
ux
chamber methods (Burba and Anderson
2005
; Foken and Nappo
2008
; Myklebust et al.
2008
)
Micrometeorological methods
the micrometeorological and
fl
Flux chamber methods
Terrain and
conditions
Difficult in hilly terrain
Possible in all terrains
Speci
c atmospheric conditions
required
Possible in all weather
conditions
Suitable for low
fl
uxes
Less suitable for low
fl
uxes
Deployment
Technical knowledge required
Easy in use
Not labor intensive
Labor intensive
Results and
representativeness
Demanding data processing
High precision
Large footprint
Small footprint
Suitable for frequent long term
measurements
Potentially influences fluxes in
measured area
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