A new study shows that oak trees continue to take in carbon dioxide well after their annual growth has stopped. The findings challenge assumptions in climate models about how much carbon forests can store. Researchers tracked sites across the eastern United States and California.
Oak trees in the eastern United States typically grew from May through July but kept photosynthesizing into October. About 36 percent of their yearly carbon uptake occurred after growth ended. In California, growth ran from December to April and stopped by August, with 26 percent of annual carbon assimilation happening afterward.
The study was led by Mukund Palat Rao of the Lamont-Doherty Earth Observatory at Columbia Climate School. "Right now, most models assume that if you have photosynthesis, you have growth," Rao said. "We find that's not the case."
Researchers combined satellite data, canopy CO2 measurements, trunk sensors, and tree ring records from 1950 onward. Growth halted quickly in hot, dry conditions while photosynthesis continued at a reduced rate.
The extra carbon may support leaves, roots, or metabolic needs rather than becoming long-term woody biomass. The team noted that climate variability could widen this gap in the future.