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Field Evaluation of Open System Chambers for Measuring Whole Canopy Gas Exchanges
Author(s) -
Baker Jeffrey T.,
Gitz Dennis C.,
Lascano Robert J.
Publication year - 2014
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2013.0449
Subject(s) - canopy , environmental science , enclosure , photosynthetically active radiation , atmospheric sciences , transpiration , infrared thermometer , microclimate , gas analyzer , fiber crop , relative humidity , hydrology (agriculture) , photosynthesis , meteorology , agronomy , malvaceae , chemistry , botany , infrared , ecology , physics , telecommunications , biochemistry , geotechnical engineering , computer science , environmental chemistry , optics , biology , engineering
The ability to monitor whole canopy CO 2 and H 2 O fluxes of crop plants in the field is needed for many research efforts ranging from plant breeding to the study of climate change effects on crops. Four portable, transparent, open system chambers for measuring canopy gas exchanges were field tested on well‐watered and fertilized cotton ( Gossypium hirsutum L.) over 6 d at Lubbock, TX, in 2010. Our objective was to (i) characterize changes in canopy microclimate variables due to chamber enclosure and (ii) evaluate chamber‐to‐chamber variability in canopy gas‐exchange parameters on ground as well as leaf area basis. Chamber wall materials reduced photosynthetically active radiation (PAR) by about 13%. Programmable data loggers controlled variable speed fans and, with one minor exception, limited heat buildup in the chambers to a maximum of <1.0°C above ambient air temperature. Differentials between incoming and outgoing atmospheric CO 2 and H 2 O concentrations were used to calculate canopy net assimilation ( A ) and transpiration ( E ) at 10‐s intervals using solenoid valve actuated sample lines connected to an infrared gas analyzer. Water use efficiency (WUE = A / E ) was then calculated and these data were averaged over both 5‐min and hourly intervals. Coefficient of variation (CV) for midday A , E , and WUE averaged 12.3, 9.7, and 5.8%, respectively. Expressing these parameters on a canopy leaf area basis produced similar CV results. These results will help guide experimental design for future research using these or similar chambers.