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Energy Utilization and Carbon Metabolism in Mediterranean Scrub Vegetation of Chile and California. I. Methods: A Transportable Cuvette Field Photosynthesis and Data Acquisition System and Representative Results for Ceanothus greggii

Walter C. Oechel and William T. Lawrence
Oecologia
Vol. 39, No. 3 (1979), pp. 321-335
Published by: Springer in cooperation with International Association for Ecology
Stable URL: http://www.jstor.org/stable/4215823
Page Count: 15
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Energy Utilization and Carbon Metabolism in Mediterranean Scrub Vegetation of Chile and California. I. Methods: A Transportable Cuvette Field Photosynthesis and Data Acquisition System and Representative Results for Ceanothus greggii
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Abstract

A transportable system for field and laboratory measurement of plant CO₂ exchange and transpiration is described. A computer based data acquisition system which controls data-logging has been successfully proven in mediterranean zones of central Chile and southern California and in the taiga of central Alaska. Six Peltier-effect cooled acrylic plastic chambers are utilized in an open infrared gas analysis system for continuous monitoring of CO₂ exchange. Chamber air temperatures automatically track ambient air temperatures or can be preset to maintain a constant temperature. Use of Peltier-effect cooling modules and electric cartridge heaters result in light-weight chambers and heat exchange units with low power requirements. No refrigeration or liquid coolant is required under most operating conditions. A unique sampling method using natural illumination and six chambers allows highly replicated determinations of the temperature and light dependence of photosynthesis and/or respiration to be made over the course of a 6-d sampling period. Measurements are made continuously 24 h/day. Diurnal CO₂ exchange patterns are determined from one chamber that tracks the ambient air temperature. The other five chambers have air temperatures fixed at distinct levels over a 35° C range. Each day the chambers are changed to another temperature level according to a randomized sampling pattern. All the data are pooled at the end of the 6-d run to construct the light and temperature response surfaces of CO₂ exchange typical of the individuals sampled. Simultaneous determinations of conductance, leaf temperature, air temperature, and light are made.

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