Free‐air CO₂ enrichment (FACE) of a poplar plantation: the POPFACE fumigation system

Abstract

Summary• A new design of free-air CO 2 enrichment (FACE) is presented that has been used to expose a poplar plantation to elevated atmospheric CO 2 concentrations in otherwise unaltered conditions, in the open.• This system releases pure CO 2 at high velocity, through a large number of small gas jets, causing rapid mixing between CO 2 and air. The theoretical and practical aspects of this design are described, with emphasis on the fluid mechanics of air-CO 2 mixing in sonic jets. Field performance data, including spectral analysis of shortterm fluctuations in CO 2 concentrations as well as temporal and spatial CO 2 control, are reported for the European project POPFACE facility.• Temporal and spatial performances of the operational POPFACE systems were adequate with average long-term CO 2 mole fractions on target. Averages over 1 min measured in the centre of the rings were within ± 20% and ± 10% of the target concentration for > 91% and > 75% of the time, respectively.• The data presented provide convincing evidence that a pure-CO 2 FACE system can achieve reliable control, in terms of the quality of the CO 2 control, with significant simplification of construction and reduced capital cost.

Free atmospheric CO<sub>2</sub> enrichment increased above ground biomass but did not affect symbiotic N<sub>2</sub>-fixation and soil carbon dynamics in a mixed deciduous stand in Wales

“…In total, 4 ambient and 4 elevated [CO 2 ] plots were randomly located within the plantation in order to form a complete replicated block design. Carbon enrichment started in April 2005 and was achieved by injecting pure CO 2 through laser-driller holes in tubing mounted on eight masts (Miglietta et al, 2001). The elevated [CO 2 ], measured at 1 min intervals, was within 30% deviation from the pre-set target concentration of 580 ppm CO 2 for 75-79% of the time during the photosynthetically active part of 2005 -2008.…”

Global food insecurity. Treatment of major food crops with elevated carbon dioxide or ozone under large-scale fully open-air conditions suggests recent models may have overestimated future yields

“…More recent designs have either pumped out of the ring to baffle upwind of the outlets (Karnosky et al 1999) or released pure CO 2 or a high concentration of ozone at supersonic velocity into the wind. At this speed the exiting air is immediately turbulent, entraining and mixing with the surrounding air (Miglietta et al 2001). Although several FACE experiments have been conducted with crops, only five locations have used large rings or plots (greater than or equal to 8 m diameter) with fully replicated (nR3) designs in each year of the experiment (Long et al 2004).…”

Mycorrhizal Hyphal Turnover as a Dominant Process for Carbon Input into Soil Organic Matter

“…The CO 2 concentration was measured at 1 min intervals, and was within 20% of the target value 89, 72 and 65% of the time for the first, second and third years. A detailed description of the FACE installation and the performance of the system is given by Miglietta et al (2001). Each circular plot (22 m diameter) was divided into six segments, and two segments each planted with trees of a single Populus genotype.…”

“…However, an increase in belowground biomass greater than the increase in aboveground biomass is often found (Norby et al, 2002;Lukac et al, 2003). To investigate the effects of elevated atmospheric CO 2 on whole ecosystems, Free Air Carbon Dioxide (CO 2 ) Enrichment (FACE) systems have been developed (Hendrey et al, 1999;Miglietta et al, 2001). FACE systems are almost unanimously considered to be the best systems to expose ecosystems to elevated atmospheric CO 2 concentrations with minimal alteration of the ambient environment (Miglietta et al, 2001).…”

“…To investigate the effects of elevated atmospheric CO 2 on whole ecosystems, Free Air Carbon Dioxide (CO 2 ) Enrichment (FACE) systems have been developed (Hendrey et al, 1999;Miglietta et al, 2001). FACE systems are almost unanimously considered to be the best systems to expose ecosystems to elevated atmospheric CO 2 concentrations with minimal alteration of the ambient environment (Miglietta et al, 2001). In the EUROFACE system, pure CO 2 is released at high velocity into the atmosphere through a very large number of small gas jets.…”