The impacts of reactive nitrogen addition has been largely studied, but mostly in the context of N-limited ecosystems such as North America, Europe and other high latitude areas. However, many tropical ecosystems are, in their natural state, N-saturated, probably as a result of high activity of symbiotic and a-symbiotic dinitrogen fixing organisms. I'm looking for research that can contribute to our understanding of how deforestation and conversion to agricultural land uses (fertilization, manure use) is affecting N dynamics within these systems and exports downstream.
We are investigating C dynamics a false time series along a land use transect in Southern Amazonia (www.carbiocial.de). I wouldn't call tropical ecosystems N-rich. Usually, there is a limited amount of N in the game, and only the fast turn-over rates keep most consumers satisfied. As soon as forest is cleared and root uptake from larger depths is reduced because of missing trees, N starts to leach out of the system. If the land is turned into grassland, litter fall is almost comparable to a forest ecosystem. If turned into agriculture, C input is reduced and so the capability to store N in organic substances slowly decreases. Fertilised N rushes through, as most tropical soils have a limited CEC, and also anionic N fixation is limited due to the positive surface charge of the soils rich in sesqui-oxides. Tropical soils under agricultural land use are often high in SOM (~3%), but a large fraction of it is recalcitrant and does not release large amounts of N. N mineralisation of less than 100 kg N ha-1 are typical.
Hope that triggers a nice discussion.