Researchers working at the Smithsonian Tropical Research Institute in Panama think the discovery that trees "turn up" their ability to capture or "fix" nitrogen from the air and release it into the soil as the forest makes a comeback has far-reaching implications for forest restoration projects to mitigate global warming.
Jefferson Hall, STRI staff scientist said that trees turn nitrogen fixation on and off according to the need for nitrogen in the system.
Hall directs the Agua Salud Project, an experiment spanning more than a square mile of the Panama Canal watershed. Researchers compare land-use options, measuring carbon storage, runoff and biodiversity to find out how mature tropical forest, native trees in forest restoration plots and abandoned pastureland compare.
They compared tree growth rate and nitrogen levels growing on pastureland abandoned two, 12, 30 and 80 years ago with trees growing in mature forests.
Tree species that "fixed" nitrogen from the atmosphere put on carbon weight up to nine times faster than their non-fixing neighbours during early stages of forest recovery. Nitrogen-fixers provided enough nitrogen fertilizer in the soil to facilitate storage of 50,000 kilograms of carbon per hectare during the first 12 years of growth.