Ecological Lessons From Free-Air CO2 Enrichment Experiments


Numerous DOE sponsored, long-term Free-Air CO2 Enrichment (FACE) experiments have provided novel insights into the ecological mechanisms controlling the cycling and storage of carbon in terrestrial ecosystems. These studies have significantly contributed to our ability to project how ecosystems respond to increasing CO2 concentrations in the Earth’s atmosphere. In this synthesis and review led by Oak Ridge National Laboratory, important lessons emerged by evaluating a set of hypotheses that initially guided the design and longevity of forested FACE experiments. Net primary productivity is increased by elevated CO2, but the response can diminish over time. Carbon accumulation in ecosystems is driven by the distribution of carbon among plant and soil components with differing turnover rates and by interactions between the carbon and nitrogen cycles. Plant community structure may change, but elevated CO2 has only minor effects on microbial community structure. FACE results have provided a strong foundation for next-generation experiments in unexplored ecosystems. FACE results also inform coupled climate-biogeochemical models of the ecological mechanisms controlling ecosystem response to the rising atmospheric CO2 concentration.


Norby, R. J., and D. R. Zak. 2011. “Ecological Lessons from Free-Air CO2 Enrichment (FACE) Experiments,” Annual Review of Ecology, Evolution, and Systematics 42, 181-203. DOI: 10.1146/annurev-ecolsys-102209-144647.