Nitrogen drives the growth of secondary forests in the Amazon: what analogies with temperate and boreal forests? A comment is made on a recent paper published on Nature (Davidson et al. 2007), in which the authors demonstrate that in the young secondary forests in the Amazon a conservative nitrogen cycle prevails and nitrogen is a key factor driving forest growth. Analogies are also discussed with recent findings on the role of nitrogen deposition on the carbon balance of temperate and boreal forests (Magnani et al. 2007).