Design and performance of a new FACE (free air carbon dioxide enrichment) system for crop and short vegetation exposure

Publication Type

Journal contribution (peer reviewed)

Authors

Fangmeier, A., Torres-Toledo, V., Franzaring, J., Damsohn, W.

Year of publication

2016

Published in

Environmental and Experimental Botany

Band/Volume

130/

DOI

10.1016/j.envexpbot.2016.06.002

Page (from - to)

151-161

<p><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;"><span style="color: #000000;">Current atmospheric CO</span><span style="color: #000000;">₂ levels are unprecedented for the last 800,000 years and require assessments of their potential effects. Free Air Carbon dioxide Enrichment (FACE) is regarded as the most appropriate exposure system for experimental field investigations. While the early FACE technology involved fans for pre-dilution of CO₂, now systems both with fans and without fans operating with pure CO₂ are employed. The most often used construction in FACE technology involves </span></span><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: DE; mso-bidi-language: AR-SA;"><span style="color: #000000;">peripheral injection</span></span><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;"><span style="color: #000000;"> from a circular or octagonal plenum with CO</span><span style="color: #000000;">₂ release pipes and jet holes surrounding the experimental plot which can create [CO₂] gradients across the plot. Here, we present a new FACE design for short vegetation (crops and grassland) that does not involve peripheral injection but distributes CO₂ directly within the plot canopy. The system involves numerous CO₂ release holes in porous tubes that hang down from the upper canopy surface and stretch into the canopy. They can be adjusted in height according to crop growth. Plot size was 2 m x 2 m which allows for a high number of replicates at low CO₂ consumption costs (6.5 tons CO₂ in one season at five replicate plots = 3.5 kg CO₂ per m² usable plot area and day during 24hr operation). System performance in terms of CO₂ control was very good both in time and space, with 93% of all instantaneous readings during daylight hours matching &plusmn;20% deviation from the set point, and low variation of [CO₂] at a given moment within the exposed canopy. Some shading (c. 4% at full canopy development) resulted from the FACE structure at the plots but hardly any other microclimatic artifacts were observed. The FACE system is of modular construction and highly flexible and adaptable to various types of short vegetation.</span></span></p>