Agricultural and Forest Meteorology 111 (2002) 171–186
Automated closed-system canopy-chamber for continuous
field-crop monitoring of CO
2
and H
2
O fluxes
P. Steduto
a,*
, Ö. Çetinkökü
a
, R. Albrizio
a
, R. Kanber
b
a
CIHEAM-IAMB, via Ceglie 9, 70010 Valenzano (BA), Italy
b
Çukurova University, Adana, Turkey
Received 30 July 2001; received in revised form 12 March 2002; accepted 22 March 2002
Abstract
An automated transient-state closed-system canopy-chamber for gas-exchange determinations of field-crops was developed
to allow unattended day and night, high frequency CO
2
and H
2
O exchange measurements, with short measurement time (15 s)
and high scanning rate (0.5 s). Environment tests on the chamber performance indicated that: atmospheric pressure variation
during operation was 10–20 Pa and limited to a few seconds; leaks introduced maximum errors of 1% in the flux calculation;
turbulence effect on CO
2
and H
2
O fluxes was not detectable; during the measurement period, temperature build-up inside the
chamber was typically within 1–2
◦
C range; photosynthetic photon flux density (R
p
) attenuation by the chamber as a whole
was in the 15–20% range; whereas, net radiation (R
n
) inside the chamber was always higher than outside by 10–20%. The
flux determinations of the automated canopy-chamber were compared with other methods. Daily evapotranspiration (E) of
artichoke obtained by canopy-chamber was at the most 4.2% lower than E obtained by high-precision weighing lysimeter.
Diurnal E and carbon exchange rates (A) of sugarbeet and marjoram crops obtained by canopy-chamber closely followed the
pattern of those obtained by the Bowen-ratio/energy-balance (BREB) method, with maximum daily underestimations of 6–8
and 5–6% for E and A, respectively. No differences in flux calculations came out when the rate of change in CO
2
and H
2
O
concentrations was derived either by linear or quadratic regressions (QR). The results of all tests and comparisons showed
that the automated chamber presented is a valuable and accurate tool for monitoring day and night CO
2
and H
2
O fluxes.
© 2002 Elsevier Science B.V. All rights reserved.
Keywords: Canopy-chamber; Gas-exchange; Evapotranspiration; Carbon exchange rate
1. Introduction
Accurate determinations of CO
2
and H
2
O fluxes of
field-crops are needed for various eco-physiological
investigations. Photosynthesis, dark respiration and
evapotranspiration responses of crops under differ-
ent experimental conditions are, indeed, crucial for
the understanding of growth and productivity and
∗
Corresponding author. Tel.: +39-080-4606224;
fax: +39-080-4606206.
E-mail address: steduto@iamb.it (P. Steduto).
supply valuable information for crop modeling as
well.
Several methods can be used for concurrent mea-
surements of water vapor and CO
2
fluxes, each with
their advantages and limitations. Micrometeorological
methods (Baldocchi et al., 1988) have the advantages
of not disturbing the environment around the plant
canopy, although their large spatial-scale requirement
is not suited for typical agronomic plot experiments
(Sharma, 1984).
Canopy-chamber methods remain the sole approach
for plot-sized experimental agriculture. Two major
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