Free-air Carbon Dioxide Enrichment (FACE) in Global Change Research: A Review

摘要: Summary There have been many experimental studies to evaluate the response of vegetation effect increases in partial pressure carbon dioxide atmosphere (p CO2) that are expected occur during next century. This knowledge is important for future protection food supplies, understanding changes natural ecosystems and quantifying role terrestrial plants regulating rate change p CO2 resulting global climate. Most our about these effects has derived from used open-top or closed chambers. These methods subject “chamber effects” caused by differences energy balance water relations may significantly modify elevated CO2. The small plot sizes imposed techniques add other limitations both interpretation results scope investigations. Free-air enrichment (FACE) provides an technique studying on ecosystem components large unenclosed plots (>20 m diameter). FACE avoids modifications microclimate chamber therefore some most reliable estimates plant Control large-scale experiments now developed extent where performance similar achieved with sophisticated closed-chamber facilities. Experience shown that, when facilities fully utilised, cost per unit usable ground area enriched CO2, lower than alternative methods. scale can support a range integrated same material, thereby achieving more complete analysis possible elevating review considers technical aspects methodology, outlines major summarises advances it allowed. Published data adequate replication limited four crop/vegetation types at three locations. two crops, cotton wheat, Maricopa, Arizona, grassland species, principally ryegrass clover, Eschikon, Switzerland. method also adapted first study mature forest trees, loblolly pine Duke Forest, North Carolina. A number progress use much smaller plots. represent over obtained previous treatment significant terms climate system clear observations wheat crops ratio sensible: latent heat transfer causes daytime warming surface vegetation. decreased loss, evident scales. allowed quantitative detailed dynamics below-ground production C accumulation systems, all surprisingly increases. Of particular note observed grown low N, there was no above-ground biomass, but increased turnover leaves input litter. cultivation appropriate agronomic trials statistically yields pasture although less suggested experiments. Against expectations, Maricopa greater relative increase yield under shortage water-sufficient crops. Acclimatory loss photosynthetic capacity widely anticipated offset photosynthesis follows initial None any evidence such loss; however, which will allow re-optimisation N distribution within reported. demonstrated be feasible effective types. information past greatly improved impacts atmospheric ecosystems.