Recuperation of nitrogen cycling in Amazonian forests following agricultural abandonment

Some 16% of the original Amazon forest has been cleared for agriculture, but much of that land is no longer in use and is starting to regrow. Such 'secondary forests' are becoming increasingly important as tropical land-use change results in larger areas that have gone through agricultural phases. A new study of Amazon forest areas between 3 and 70 years into their recovery reveals nitrogen and phosphorus cycling processes consistent with large losses of nitrogen during land use change. Nitrogen availability is ephemeral, and readily disrupted by either natural or anthropogenic disturbance. Understanding how the nutrient cycling processes of secondary forest succession should contribute to the better management Amazonian ecosystems. Elsewhere in the nitrogen cycle, an analysis of virtually all extant data on open oceanic nitrification, in conjunction with a global ecosystem model, demonstrates that the generally accepted assumptions concerning its distribution are incorrect. Much of the nitrate taken up by the oceans is generated through recent nitrification near the surface and, at the global scale, nitrification accounts for about half of the nitrate consumed by growing phytoplankton. This means that many previous attempts to quantify marine carbon export may be significant overestimates.