High-CO2 Oaks Unlock 29% More Soil Nitrogen Through Roots, Sustaining Faster Growth
Updated
Updated · Earth.com · Jul 31
High-CO2 Oaks Unlock 29% More Soil Nitrogen Through Roots, Sustaining Faster Growth
3 articles · Updated · Earth.com · Jul 31
Summary
Six years into a Staffordshire field experiment, 180-year-old English oaks exposed to 573 ppm CO2 grew more wood by tapping extra soil nitrogen rather than depleting reserves.
A Science Advances study found the trees fed soil microbes with root exudates, lifting usable nitrogen release 29%—about 23 pounds an acre—while the trees absorbed an extra 12 pounds an acre.
Soil cores under treated oaks showed 39% more fine roots, 26% higher CO2 release and roughly 30% faster microbial nitrogen liberation, with a 75% spring spike at budburst before drought muted the effect.
Nitrogen losses did not rise as expected: nitrate never built up, conversion to nitrate slowed by about half in spring and summer, and nitrous oxide showed no increase in core measurements.
The findings suggest some forests could keep storing more carbon under rising CO2 for decades, though the benefit may fade as accessible nitrogen shrinks or where another nutrient—such as phosphorus—limits growth.