The availability of molybdenum in soils, and not phosphorous as previously thought, may be limiting the natural input of nitrogen into tropical forests, according to a study published online in Nature Geoscience.
The primary natural input of nitrogen into ecosystems, known as bacterial nitrogen fixation, influences plant growth and carbon exchange from local to global scales. Lars Hedin and colleagues treated soils from a Panamanian forest with molybdenum, phosphorous fertiliser contaminated with molybdenum, and molybdenum-free phosphorous. They find that soils treated with molybdenum show a sharp increase in nitrogen fixation by free-living bacteria. Phosphorous alone has no effect on nitrogen fixation, a result that contradicts current thinking.