Northern Forest Remains Productive After Decade of Elevated CO2 and O3


The accumulation of anthropogenic CO2 in the Earth’s atmosphere and its impact on the rate of climate warming also impacts plant growth. Here, DOE-funded scientists synthesize data from the Rhinelander FACE (Free Air CO2 Enrichment) experiment in which three developing northern forests have been exposed to combinations of elevated CO2 and O3. Enhanced growth (~26% increase) under elevated CO2 was sustained by greater root exploration of soil for growth-limiting nitrogen, as well as rapid rates of litter decomposition and microbial nitrogen release during decay. Despite initial declines in forest productivity under elevated O3, compensatory growth of O3-tolerant trees resulted in equivalent growth under ambient and elevated O3. After a decade, productivity has remained enhanced under elevated CO2 and has recovered under elevated O3. The mechanisms responsible for these CO2 and O3 effects need to be represented in coupled climate-biogeochemical models simulating interactions between the global carbon cycle and climate warming.


Zak, D. R., K. S. Pregitzer, M. E. Kubiske, and A. J. Burton. 2011. “Forest Productivity Under Elevated CO2 and O3: Positive Feedbacks to Soil N Cycling Sustain Decade-Long Net Primary Productivity Enhancement by CO2,” Ecology Letters, DOI: 10.1111/j.1461-0248.2011.01692.x.